~-&;~ ~
Lecture Notes in Earth Sciences Editors: S. Bhattacharji, Brooklyn G. M. Friedman, Brooklyn and Troy H. J. Neug...
15 downloads
757 Views
29MB Size
Report
This content was uploaded by our users and we assume good faith they have the permission to share this book. If you own the copyright to this book and it is wrongfully on our website, we offer a simple DMCA procedure to remove your content from our site. Start by pressing the button below!
Report copyright / DMCA form
~-&;~ ~
Lecture Notes in Earth Sciences Editors: S. Bhattacharji, Brooklyn G. M. Friedman, Brooklyn and Troy H. J. Neugebauer, Bonn A. Seilacher, Tuebingen
- iZ',','g
46
Gianni Galli
Temporal and Spatial Patterns in Carbonate Platforms
Springer-Verlag Berlin Heidelberg NewYork London Paris Tokyo Hong Kong Barcelona Budapest
Author Dr. Gianni Galli Via Samacchini 5 1-40141 Bologna
"For all Lecture Notes in Earth Sciences published Ull now please see final pages of the book"
ISBN 3-540-56231-1 Springer-Verlag Berlin Heidelberg New York ISBN 0-387-56231-1 Springer-Verlag New York Berlin Heidelberg
Library of Congress Cataloging-in-Publication Data Galli, Gianni, 1956Temporal and spatial patterns in carbonate platforms / Gianni Galli. p. cm. - (lecture notes in earth sciences; 46) Includes bibliographical references. ISBN 3-540-56231 - 1 (Berlin: acid-free). - ISBN 0-387-56231-1 (New York: acid-free) 1. Rocks, Carbonate. 2. Sedimentation and deposition. I. Title. II. Series. QE471.15.C3G35 1993 552' .58-dc20 93-8317 This work is subject to copyright. All rights are reserved, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, re-use of illustrations, recitation, broadcasting, reproduction on microfilms or in any other way, and storage in data banks. Duplication of this publication or parts thereof is permitted only under the provisions of the German Copyright Law of September 9, 1965, in its current version, and permission for use must always be obtained from Springer-Verlag. Violations are liable for prosecution under the German Copyright Law. © Springer-Verlag Berlin Heidelberg 1993 Printed in Germany Typesetting: Camera ready by author 32/3140-543210 - Printed on acid-free paper
ACKNOWLEDGMENTS
I w o u l d like to e x p r e s s my h e l p e d me d u r i n g t h i s 1 2 - y r
s i n c e r e t h a n k s to long work project,
all of t h o s e w h o s t a r t e d in 1981.
Prof.G.B.Vai ( U n i v e r s i t y of B o l o g n a ) a l l o w e d me to m a k e a f r e s h s t a r t at the b e g i n n i n g by i n t r o d u c i n g me to the f i e l d g e o l o g y of the C a r n i c A l p s a n d l a t e r a c t i n g as a s u p e r v i s o r of m y P h D thesis, He also oriented my mental attitude towards a neocatastrophist a p p r o a c h of g e o l o g i c a l p r o c e s s e s . Prof.R.N.Ginsburg allowed Florida platform in 1987 enjoying the fresh breeze Fullbright tenure,
me to s t u d y Pleistocene cores of and put me in the condition of of F i s h e r Island Station during a
Prof.C.G,St.C,Kendall g a v e a c c e s s to South Carolina University, probably s i m u l a t i o n p r o g r a m s e x i s t i n g today,
the one
S e d p a k p r o g r a m at the of the m o s t p o w e r f u l
D r , M i a V a n S t e e n w i n k e l q u i t e k i n d l y s e n t me h e r t h e s i s in 1 9 8 8 which allowed the development of the sequence stratigraphy a p p r o a c h to the c a s e h i s t o r i e s s u m m a r i z e d in this work. I am a l s o i n d e b t e d to Prof. J o n a t h a n T e n n e n b a u m (Fusion Energy Foundation) who pushed me to develop section V on the relativistic distribution of e v e n t h o r i z o n s ,
TABLE OF C O N T E N T S
1
INTRODUCTION ..................................................
PART
Krikogenetic
rejuvenation
Krikogenetic
quiescence
periods periods
........................
..........................
I ........................................................ INTRODUCTION ............................................. FACIES BELTS ............................................ Shallow
ramp .......................................
Thin-bedded
alternations
Thick-bedded
alternations
Proximality-distality Intermediate Deep
......................
trends
0nlap
geometry
0fflap
SEQUENCE Shelf
17
~I ~6
tract
tract tract
surface
Transgressive Maximum
tract
facies
facies
Ravinement
~I
....................................
facies
Lowstand
27 31
RAMPS . . . . . . . . . . . . . . . . . . . . . . . . . .
facies
margin
15
2A
STRATIGRAPHY ...................................
Highstand
13
.....................................
geometry
Transgressive
8 12
.......................
ramp ..................................
OF I N T R A S H E L F
A 7
.....................
ramp ..........................................
GEOMETRIES
3
..........................
............................. ..............................
.................................
surface
flooding
.........................
..............................
surface
...........................
51 55 57 57 57 58 58 59
M E C H A N I S M S OF F O R M A T I O N O F O N L A P R A M P S . . . . . . . . . . . . . . . . . . 60 FORT THOMPSON FORMATION,PLEISTOCENE,FLORIDA P L A T F O R M .... 6 9 Introduction
.......................................
69
Lithofacies
and
71
Marine
swamp
associations Shallow Deep
Maximum
Early Late
flooding
.........................
............................ surface
facies
highstand
facies facies
......................
tract
....................
tract tract
88 88
95
........
..................................
associations
83 83
...................
.........................................
Shallow
78 78
92
.......................................
studies
76
..................
FORMATION,JURASSIC,VENETIANALPS
Introduction area
..............................
surface
highstand
GRIGI"
Facies
75
surface
Transgressive
Study
73
................................
sequence
Ravinement
71
..............................
ramp .....................................
Transgressive
Previous
..............
ramp ..................................
Depositional
"CALCARI
setting
Bay ....................................
Freshwater Facies
environmental
97 97 99 I01
...............................
I01
ramp .................................
102
Vlll
Oncolite
grainstones
Bioclast-lithoclast Lime
mudstones
Intermediate
wackestones
....................
107 109
sequence
.............................
facies
margin
tract ...................
facies
highstand
tract ..................
121
tract ....................
122
D E V O N I A N CARBONATE P L A T F O R M , C A R N I C
...............................
ramp .................................
Pond
facies .............................
Intermediate
ramp ............................
Intraclast
shoal ........................
142 143
grain-wackestones
SHORELINE sequence
.............................
facies
tract ........................
Highstand
facies
facies
remarks
tract ...................
tract .......................
................................
PART II . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C O M P U T E R SIMULATION OF CLASTIC WEDGES . . . . . . . . . . . . . . . . . . Introduction
......................................
pattern
Convergent
..................................
pattern pattern
Concludin~ Introduction
Highstand
155 155 159
179
sequence
MASSIF.181
.......................
thinning-upward and
unit .............
thickening-upward sequence
facies
Transgressive
154
169
depositional
Lowstand
153
................................
...................................... and
153
.................................
depositional Fining-
151 152
162
(CRETACEOUS-PALEOCENE),GARGANO
Coarsenin E-
149 151
................................
remarks
SLOPE CARBONATES
144
SEQUENCE,PLEISTOCENE .......... 149
......................................
Lowstand
Concludin~
............
model ................................
Transgressive
Second
142 143
Introduction
First
139 142
Brachiopod
Depositional
Diversent
130 139
ramp ....................................
Depositional
Parallel
124
ALPS,ITALY .......... 130
......................................
Shallow
117 I19
...............................
associations
i15 117
tract .................
facies facies
deposition
Introduction
...................
...................................
highstand
Shelf
"CAPO RIZZUTO"
I05 109
Early
Deep
105
.................
wackestones
Transgressive
Facies
105
Lithiotis Depositional
of
.... 1 0 4
..........................
ramp ....................................
Paleobathymetry
Model
..... 1 0 2
grain-packstones
Skeletal
Late
and
ramp ............................
Oolite Deep
packstones
grain-packstones
facies
184
unit ....... 187
......................
tract ........................
facies
181 184
tract ...................
tract .......................
19A 19d i97 207
IX
Shelf
margin
facies
Distal Proximal Third
sequence
facies
Transgressive Highstand
facies
Proximal
MIDDLE
Introduction Shallow
tract
...................
215
........................
216
clinoforms
.....................
216
.......................
216
................................
BUILDUPS,DOLOMITES
...........
......................................
ramp .................................
ramp .........................................
Deep PART
213 215
ramp ......................................
Intermediate
209
.......................
tract
CARBONATE
209 209
........................
clinoforms
remarks
TRIASSIC
tract
facies
Distal Concluding
....................
lobe ...........................
depositional Lowstand
tract
lobe .............................
218 223 223 225 226 227
III ....................................................
229
MODAL SEQUENCE ......................................... PART IV ..................................................... SHORT-TERM SEA-LEVEL FALLS : AN INDICATOR OF GEOIDAL PULSES? ................................................
230
Megabreccias
......................................
Seismoturbidites Are or
megabreccias vertical
Drowning Relief
PART
..................................
of
the
product
of
Hierarchy Geometrical Biological Event
2~9
tectonics?
............................
252
platforms
258
...................
.................................
......................................
Relativistic
Generation
237
carbonate
inversions
Neg-entropy
23A
oompressional
V ...................................................... RELATIVISTIC DISTRIBUTION OF "EVENT HORIZONS". ......... Introduction
233
concept
of
event
.....................
....................................... of of
singularities singularities
distribution evolution
horizons
261 281 282 282 286 288
.......................
289
........................
290
of
singularities
.........
..............................
....................................
REFERENCES ..................................................
291 295 297 300
I n t r o d u o t ion
"The geological history,as expressed by the stratigraphic column,is basically composed of cycles of sedimentation, stratification and magmatism which correlate with relative changes in sea level d e t e r m i n e d in turn by d i f f e r e n t types of crustal movements. The classical sequence of stages "transgression - inundation - differentiation - regression emergence" is b e l i e v e d to reflect the d e f o r m a t i o n p h a s e s of a g e o t e c t o n i c cycle" (Wezel,1988: p.37). The concept of g e o t e c t o n i c cycle is f u n d a m e n t a l in because it links t e c t o n i c s with s e d i m e n t a r y p r o c e s s e s .
geology
According to Wezel (1988) the geotectonic cycle is an e x p r e s s i o n of c y c l i c v a r i a t i o n s in the b e h a v i o r of the crust; more precisely,it is a g e o d y n a m i c response to the Earth's variations in the rate of r o t a t i o n (M~rner,19869 Whyte,1977~ Carey,1976).Based on a g l o b a l analysis of g e o t e c t o n i c data, synchronous e p i s o d e s of intense global swelling, governed by cyclically ordered diastrophic processes, were identified (Wezel,1985;1988). The p r o c e s s l e a d i n g to these swells was t e r m e d k r i k o g e n e s i s (Wezel, 1988).It b a s i c a l l y c o n s i s t s of not steady, localized, migratory vertical movements linked to m a n t l e diapirism and c o n c e n t r a t e d in single z o n e s . T h e o v e r l y i n g crust a d j u s t s itself to mantle motions induced by k r i k o g e n e s i s , w i t h the f o r m a t i o n of transient troughs and swells ('touche-de-piano' tectonics).This mechanism was individuated in several areas (Wezel,1988). The h i s t o r y of the E a r t h is d e s c r i b e d by six e p i s o d e s that repeat in the same way in the c o u r s e of g e o l o g i c a l time.Their d u r a t i o n p r o g r e s s i v e l y d e c r e a s e s : t h e first c y c l e has a d u r a t i o n of about 200 m i l l i o n years, the f o l l o w i n g , y o u n g e r c y c l e s lasted 1 5 0 , I 1 5 , 6 5 , A 5 and 20 m.y. These cycles can be t r a c e d along a time-spiral,its length representing the time (Fig.l). Each cycle of d e p o s i t i o n and uplift can be subdivided into the following phases: krikogenesis, inundation, regression and e m e r g e n c e . The last phase is p r e c e e d e d by a t e c t o g e n i c phase, linked to an i n c r e a s e in t e c t o n i c a c t i v i t y (Fig.2).
G EOSYNCLIlv4 I NUNDA.I.IOIv
uPPE. oo _
\
0 0
LU
co
uj
0
h..
o
0
0
+ "eln~. otv
"~
\
flOGEN! c
Fig.l - Time spiral showing the six ma~or sedimentary cycles of Earth history, each separated by a tectogenetic phase (Wezel,1976:p.87).Each cycle is divisible into four main phases. The geological history is marked by the rhythm of k riko~enetic rejuvenation and k~ikogenetic quiescence periods (Wezel,1988), each punctuated by a recurrent set of changes of different organic and inorganic processes.
== =_
== 13Z O
~oOoOoO O 0 )O ° O ~ O G o oDD •
[ ~
skeletal wackestone hurricane mud mangrove peat fresh-water mudstone peat Pleistocene
Fig.lO - Schematic profile Everglades (Scholi,1963).
of
the
recent
sediments
close
to
the
T h e s e a r e a s m a y be t h e s i t e s of f o r m a t i o n of p i s o i d s a n d v a d o s e diagenetic features which may also form on top of shoals. Radial oolite horizons may occur in the more sheltered, hypersaline intershoal areas. Shoals and intershoal associations:
areas
are
organized
into
I) t h i n - b e d d e d alternations; 2) t h i c k - b e d d e d a l t e r n a t i o n 8
two
main
facies
and
Thin-bedded alternations
These alternations consist of a few cm to 20 cm thin, calcarenite calcisiltite layers interbedded with black, cm-thin argillaceous calcilutites which contain vegetal debris and plant remains. Bases and tops of calcarenite and calcisiltite beds are sharp. Physical sedimentary structures are gutter casts at the bases of coarser grained beds, pinch-outs within calcilutites and very thin mm to c m thin lenses of shell debris, or cm-thiok mud storm horizons (Fig.ll). Calcarenite and calcisiltite mud layers frequently display a vertical thickening-upward trend which is a c c o m p a n i e d by an increase in t h i c k n e s s a n d n u m b e r of s t o r m h o r i z o n s and grain size (Fig,12). In o t h e r cases thicker beds are homogeneous mudstones with rare ostracods.
]6
Fig.ll - Thin-bedded alternations. A,B: m u d s t o n e s intercalated w i t h m a r l s ( ' C a l c a r i G r i g i ' F o r m a t i o n , s e c t i o n s #5 a n d #19). C; very thin, storm-generated lamination (Giver i a n - F r a s n i a n platform, Belgium). D: H u r r i c a n e and winter-storm senerated l a y e r s ( C r a n e Key: F l o r i d a B a y ) . There
are
basically
two
end-members
I) c a l c a r e n i t e s with fragments 2) s t r u c t u r e l e s s mud.
of
of
thicker
bioclasts
and
beds: shell
debris;
There is a l a t e r a l transition, over short distances, between these two end members,accompanied by a set of s t r u c t u r e and compositional variations, as is s h o w n in F i g . 1 3 . A modern analogue of these marlstone - limestone alternations o c c u r s c l o s e to t h e l a n d w a r d m o s t termination of F l o r i d a Bay, c l o s e to t h e land ( F i g . l O ) . T h e r e , mud layers are aragonite and contain sparse detritus of m o l l u s k s , foraminifers and
]7
cross laminated mud with vegetal debris
hummocky
_."::L.-c..--" ---." ----,.
algal stromatolite
-L :.".'.'.'....-:-.-:
:'.:'1
•
.
,
.
-
poorly sorted calcarenite laminae
,~-4,#~.~.J,,4;,'~:A
-.... •.'..'.'"
: J,"'" ~ " ' ~ ' " ; '
15 cm
,
.
.
roots
.J
winter storm deposit
.
°
.
•
-- algal mats
t
~,---~ ~-,--~.. ~, :.~:~':.~:~ . ~%~t ~ " ~_~.'~-[t
"dli "..:' :~." ~ f e n est rae •
algal laminae
_
cmO
.
carbonate grains & algal mats poorly sorted c a l c a re n i t e algal laminated
~--sediment Fig.12 Florida
Details of recent Bay (Galli,1990),
calcareous angiosperms
algae. The and peat,
mud
thin-bedded
contains
alternations
mangrove
plant
from
debris,
Sharp bases, l a c k of b i o t u r b a t i o n and lags at the b a s e s of individual interbeds evidence for 'event' deposition. These thin calcarenite-calcisiltite interbeds are analogous to interpreted distal tempestites d e s c r i b e d by B r e t t ( 1 9 8 3 ) , A i g n e r (1985) and Van Steenwinkel (1988). Their location and stratigraphic relationships with other facies types suggest that they formed in a very shallow setting, They are interpreted as the finer tails of onshore storms directed towards progressively shallower zones. Interbeds are also similar to hurricane-generated thinly bedded grainstones interbedded with organic-rich layers d e s c r i b e d by W a n l e s s , et al. (1988) f r o m C a i c o s p l a t f o r m , Mud layers represent hurricane-generated deposits~ they are s i m i l a r to m u d l a y e r s d e p o s i t e d by h u r r i c a n e s Donna and Betsy in F l o r i d a B a y ( P r a y , 1 9 6 6 ; ~ G a l l i , 1 9 9 0 9 F i g , 1 2 ) .
Thick-bedded
These
are
characterized
by
alternations
fining-upward
calcarenites
and
18
19
=last grains 2
..~,~.. ~ ~ . 4.4 ?~.~,..~£~:..~~/ ".-..3 ~-~..'xC.¢4
shells
•"[-... '.'.-'..
,J
m0-
matr,×
~ ~ s" ~ t- -_i n_t_ _ _ _ ~racla _
grains
Fig.13 - Fining-leftward grain size trends and compositional c h a n g e s of t h i n - b e d d e d alternations (Devonian platform, Carnic Alps) :brachiopod coquina (A)-->bioclast and intraclast grains (B)-->peloidal detritus with sparse bioclasts interbedded with mud laminae (C)-->mud laminae with sparse detritus interbedded with mudstones (D). T h e s e t r e n d s r e s u l t f r o m an o n s h o r e storm c u r r e n t ( t o w a r d s t h e left). T h e s k e t c h s h o w s a reconstruction of the paleoenvironment and the corresponding strat igraphic log.
calcisiltites, normally between 0.70 and 2m thick, interbedded with thin calcareous black mudstones containing scarse fossils. Thick beds are characterized b y the f o l l o w i n g m o d a l t r i p a r t i t e division I)
2) 3)
(Fig.14):
a b a s a l s h e l l lag; an i n t e r m e d i a t e mudstone-wackestone unit; and a parallel-laminated, well sorted upper grainstone
The upper mudstones
u n i t m a y be is planar
missing. The lower contact to e r o s i o n a l , as is s h o w n
unit.
above black by erosional
20
Fig. IA Thick-bedded alternation ('Calcari Grigi' Formation:section #25). This composite bed consists of a s c o u r e d c o n t a c t a b o v e l i m e m u d s t o n e s , a b a s a l lag z o n e c o m p o s e d of L i t h i o t i s shells and other bioclasts (B), a n i n t e r m e d i a t e wackestone unit consisting of a m a l g a m a t e d dm-thick layers, and an upper, hummocky-cross bedded unit with well sorted grainstones (A). t r a c e s a n d g u t t e r c a s t s . T h e l o w e r s h e l l l a g is p o o r l y sorted and contains lithoclasts eroded from the underlying muddy interface, in a d d i t i o n to v a r i o u s t y p e s of u n s o r t e d bioclasts. Imbrications w i t h i n m o r e d e n s e l y p a c k e d u n i t s c o n t r i b u t e to t h e development of a better sorting. The transition to the intermediate u n i t is s h a r p 9 the m u d d y u n i t a p p e a r s h o m o g e n e o u s 9 sedimentary structures were possibly present (such as faint
21
PROXIMAL
DISTAL
INTERMEDIATE RAMP
SHALLOW RAMP
f ~
i
lw
THIN-BEDDED ALTERNATIONS
THICK-BEDDED
m0m 0
E
l m
22
undulations: Fig. IA) but were destroyed by non figurative b i o t u r b a t i o n w h i c h is of v a r y i n g i n t e n s i t y . The t r a n s i t i o n to the o v e r l y i n g unit is diffuse. The thinner upper unit is characterized by well sorted, laminated grainstones with h u m m o c k y , to w a v e r i p p l e l a m i n a t i o n , or p a r a l l e l lamination. This s e q u e n c e is s i m i l a r to o t h e r nearshore storm deposits d e s c r i b e d by K r e i s a (1982), B r e n c h l e y , et a i . ( 1 9 7 9 ) and K u m a r and S a n d e r s (1976), among others.Storms and hurricanes are m a i n l y r e s p o n s i b l e for the f o r m a t i o n of these sequences. High flow r e g i m e s can be i n f e r r e d from a n u m b e r of features, such as spar c a l c i t e cement, s h e l t e r p o r o s i t y cement, a m a l g a m a t e d beds, well s o r t e d laminae and h u m m o c k y c r o s s - l a m i n a t i o n . B a s e d on d i f f e r e n t p r o p o r t i o n s of the i n t e r m e d i a t e and lower units, different types of s e q u e n c e s can be r e c o g n i z e d . They r e p r e s e n t a s p e c t r u m of l a n d w a r d to s e a w a r d t r a n s i t i o n s , w i t h a landward tendency towards a decrease in shell percentage. Fig.15, t a k e n from the 'Calcari Grigi' Formation, illustrates c h a n g e s in b e d d i n g styles g o i n g from the i n t e r m e d i a t e ramp to marsh environments typical of the landwardmost site of the s h a l l o w ramp. This t r e n d is a n a l o g o u s to that o c c u r r i n g in F l o r i d a Bay9 the Holocene platform, 36 km wide, does not e x c e e d 12 m in depth. The floor which gently dips towards south and southeast
Fig.15 - A~B~C: c h a n g e s in b e d d i n g s t y l e s of t h i c k - b e d d e d and t h i n - b e d d e d a l t e r n a t i o n s from a r e a s c l o s e r to the s h a l l o w ramp (right) to the i n t e r m e d i a t e r a m p (left) in the 'Calcari Grigi' Formation (sections #19 : A,B-->#6 : C), Closer to the intermediate ramp (C) there are no m u d s t o n e interbeds within thin-bedded alternations which are distinguished from the underlying thick-bedded alternations by their small thicknesses. In more distal positions lime mudstone become predominating and t h i c k - b e d d e d alternations, interbedded with b i o t u r b a t e d t h i c k e r sets of lime m u d s t o n e s , s t a n d out c l e a r l y on o u t c r o p faces. P r o x i m a l and d i s t a l t h i n - b e d d e d a l t e r n a t i o n s are o r g a n i z e d into t h i c k e n i n s - u p w a r d t r e n d s (cf. Fis.12). D~E~F: c l o s e r v i e w s of c o m p o s i t i o n a l changes from the s h a l l o w ramp (D,E) to the i n t e r m e d i a t e ramp (F), w h e r e s h a l l o w - w a t e r forms of L ~ t h i o t ~ s are r e p l a c e d by t h i n - s h e l l e d m o l l u s k s . The sketches below show proximal (section #6) and distal (section #19) alternations, and facies types ('Calcari Grigi'Formation).
23
NW
SE
"~. mud banks
patch r e ~ s ' ~ ~ J ~
Florida Ray
sand shoal
outer reeP--
5
4
3 2 km
t
1
20m
0
sJ.
LAND
SEA
~"
"-"[
r," "
Crane Key 2 Safety Valve 3
mangrove 1 i mud bank 1 flat Murray K e y 1
.'.•_.
-.- ~ iiii
"', ::... "-'.
",.C :.'£' ...
!?I
:'.'2, •
(~
I
angiosperm
grainstone
gastropod
packstone
peneroplid
wacke-mudstone
Halimeda lm
-~-~-.- pelecypod
'-'--]
fresh
water swamps
.... .... ... •• ,...
.i
.... ... . . :-" :
- :5
Molasses 4 reef
red mangrove peat .... MBH4•.I
coral
Fig,16 Bathymetric profile of the Florida platform (Enos,1977) and s t r a t i g r a p h i c logs (I: C r a i g h e a d , 1 9 6 9 ; 2 : E n o s and P e r k i n s , 1 9 7 9 ; 3 : A i g n e r , 1 9 8 5 ; A : E n o s , 1 9 7 7 ) .
(Atlantic Ocean) is complicated by topographic relieves c o n s t i t u t e d by c a r b o n a t e shoals, banks and p a t c h - r e e f s . S e d i m e n t a t i o n took place d u r i n g a phase of r e l a t i v e s e a - l e v e l rise (Scholl,et ai.,1969). The flooding of the platform i n i t i a t e d 8500 years ago. A s l o w i n g in the s e a - l e v e l rise took place 5500 years ago (30 c m / 1 0 0 0 years). The cross s e c t i o n of Fig.16, oriented normal to the strike of the p l a t f o r m , from open to s e m i r e s t r i c t e d e n v i r o n m e n t s
northwestsoutheast, reflects a transition (Enos,1977).
The cycles a c t u a l l y d e v e l o p i n g in F l o r i d a Bay are a s y m m e t r i c , transgressive sequences c a p p e d by i n t e r t i d a l and s u p r a t i d a l d e p o s i t s (Enos and P e r k i n s , 1 9 7 9 ) . T h e y c o n s i s t of: i) a basal c o a r s e m o l l u s k g r a i n s t o n e and p a c k s t o n e (shallow m a r i n e bay);
24
2) a mud b a n k c o n t a i n i n g few s c a t t e r e d o r g a n i s m s 9 and 3) an upper island d e p o s i t consisting of algal l a m i n a t e d s e d i m e n t s and c m - t h i c k s t o r m layers. These banks are intercepted by onshore directed storms ( h u r r i c a n e s and w i n t e r storms) and in s e c t i o n show a w i n d w a r d side and a l e e w a r d side dipping downcurrent (Fig.17). The w i n d w a r d side is steep and c h a r a c t e r i z e d by a nip and a b e a c h ridge c o v e r e d by shells, i n t r a c l a s t s and v e g e t a l debris. T h e s e keys c o n s i s t of l o w - i n c l i n e d sets c o m p o s e d of s t a c k e d graded layers each given by a basal lag (packstones, w a c k e s t o n e s w i t h m o l l u s k s and f o r a m i n i f e r s ) o v e r l a i n by m o l l u s k foraminifer mudstones. The leeward side is covered by an i n t e r t i d a l - s u p r a t i d a l flat w h i c h is the site of d e p o s i t i o n of fine-grained peloidal and bioclast detritus. A similar s t r u c t u r e is shown in F i g . 1 7 (below).
In both m o d e r n and a n c i e n t s i t u a t i o n s l a n d w a r d c h a n g e s in c y c l e thicknesses, composition and grain-size trends reflect the a c t i o n of o n s h o r e - d i r e c t e d s t o r m flows d e c r e a s i n g in i n t e n s i t y towards s h a l l o w e r areas. T h e s e trends are a n a l o g o u s to those d e s c r i b e d by B o u r r o u l h - l e Jan, et a i . ( 1 9 8 5 ) and to the case h i s t o r y r e p o r t e d by A i g n e r (1985) w h o d e t a i l e d the s t r u c t u r e of spillover lobes consisting of s u c c e s s i v e inputs of onshore d i r e c t e d sediments.
Proximality-distality
trends
The d e c r e a s e of s t o r m e f f e c t s t o w a r d s deeper, offshore water was demonstrated by Aigner (1985) in modern and ancient s i t u a t i o n s d o m i n a t e d by a p r o g r a d a t i o n a l , r e g r e s s i v e trend. It shows that: "The p e r c e n t a g e of sand, s t o r m layer t h i c k n e s s and grain size, as well as the d e g r e e of a m a l g a m a t i o n show a continuously decreasing trend from s h a l l o w to d e e p e r water, while bioturbation generally decreases" (Aigner,1982,1985). This c o n c e p t is not a p p l i c a b l e in the c a s e s e x a m i n e d f u r t h e r b e l o w w h e r e the v a r i o u s p a r a m e t e r s d i s p l a y o p p o s i t e trends. A distal p o s i t i o n for t h i n - b e d d e d the f o l l o w i n g features:
alternations
is
indicated
by
25 Windward
C
o
Leeward
n
g
l
o
~
~
,
.
~
,
k Wacl<estone
\ Basal sheet lag
lOOm
0m
eagrass
20 m
,,,,,,,,,
INI "I
II
~i
I
II
II
I IIIIIIIIII
I
IIIIII
III
II
4
Fig.17 - Above: cross s e c t i o n of a m u d m o u n d from F l o r i d a Bay (Upper C r o s s Bank: Bosence,1988). Below: front view of an a n c i e n t a n a l o g u e from the 'Calcari GriEi' Formation (section #6) formed by a stacked lenses of skeletal wackestones i n t e r b e d d e d with thin lime m u d s t o n e s
I. lack of basal units; 2. flat bases; 3. s c a r c i t y of a m a l g a m a t i o n s ; 4. small t h i c k n e s s e s and fine g r a i n e d A proximal position by the following:
for
the
size
thick-bedded
of material. alternations
is
shown
I. o c c u r r e n c e of complete storm sequences (tripartite division); 2. e r o s i o n a l surfaces; 3. thick basal u n i t s with lags and a g r a i n s t o n e texture; ~. amalEamations of sequences; s t a c k i n E of basal units. S t o r m d e p o s i t s here are a main result of an o n s h o r e s e d i m e n t t r a n s p o r t in a shallow, n e a r s h o r e water, as a direct e f f e c t of w i n d - d r i f t currents. There are two p o s s i b l e c a u s e s for this: I) the deep ramp is not deep e n o u E h to f a v o u r o f f s h o r e s e d i m e n t
26
t r a n s p o r t d u e to g r a d i e n t c u r r e n t s a n d 2) the o v e r a l l t r e n d is t r a n s g r e s s i v e .
bottom
return
flows;
and
'Proximal' and 'distal' here are used in a relative meaning:they r e f e r to the n e a r n e s s to t h e s o u r c e a r e a of the material which is transported landward, Variations in the a m o u n t s of b i o c l a s t s v e r s u s m u d c o n t e n t , and thickness of b e d s interbedded with lagoonal micrites reflect proximality distality trends. P r o x i m a l b e d s o c c u r in m o r e d e e p e r l a g o o n a l a r e a s w h i c h a r e the s o u r c e of t h e b i o c l a s t m a t e r i a l transported landward; they are bioclast-rich, thick-bedded grainstones and packstones located s e a w a r d , c l o s e to t h e i n t e r m e d i a t e ramp. Distal beds are mud-supported thin beds containing scattered b i o c l a s t s . T h e f r e q u e n c y of t e m p e s t i t e s decreases landward, as is s h o w n in a ' i s o t e m p e s t i t e ' map obtained from the 'Calcari Grigi' Formation' (Galli,1990:Fig.2). In t h e s e 180 ° out
situations of phase
the proximality - distality criterions are w i t h r e s p e c t to t h e proximality-distality
Proximal
Distal
~ _ . . . . 9 ~ Y ~.'~~'.;-" ~ "
grainstone
-
lag Intraclasts Amalgamations
r-
Grain size
C
Bed thickness
-
-] Peat Bioclasts
Thick- bedded alternations Fig.18 - Proximality-distality shallow ramp.
Thin-bedded alternations trends
in
the
intermediate
-
27
trends d e s c r i b e d by A i g n e r (1985), and others, mainly b e c a u s e the s i t u a t i o n s e n c o u n t e r e d are c h a r a c t e r i z e d by t r a n s g r e s s i v e , r e t r o g r a d a t i o n a l trends, w h e r e a s the t r e n d s d e s c r i b e d by A i g n e r (1985) a p p l y to p r o g r a d a t i o n a l , r e g r e s s i v e systems. In o r d e r to avoid m i s l e a d i n g i n t e r p r e t a t i o n s , t h e use of the p r o x i m a l i t y d i s t a l i t y c r i t e r i o n must be c o n f r o n t e d w i t h other i n d e p e n d e n t p e t r o g r a p h i c and g e o l o g i c a l data.
Intermediate
ramp
The i n t e r m e d i a t e r a m p is located b e t w e e n the lower and the upper limit of wave action. This is a high-energy area c h a r a c t e r i z e d by a rough t o p o g r a p h y and i n t e r c e p t e d by waves and c u r r e n t s which are m a i n l y r e s p o n s i b l e for a c o m p l e x and l e n t i c u l a r geometry. The large size of bedforms, several m in wavelength, points to a d e p o s i t i o n as sand blankets. C o m m o n sedimentary structures are e r o s i o n a l features, channels and m e g a r i p p l e s m i g r a t i n g u n d e r e p i s o d i c h i g h - e n e r g y conditions. The distribution of sediment in close proximity to the i n t e r m e d i a t e ramp is c o n t r o l l e d by the u n d e r l y i n g t o p o g r a p h i c s u r f a c e s . T h e r e are d i f f e r e n t belts: n a m e l y I) skeletal sands9 and 2) c o l d - r i c h sands. T h e y form r e s p e c t i v e l y I) h i g h - e n e r g y skeletal beaches; and 2) sandwaves. T h e s e two belts may o c c u r
Beach sands Sandwaves Lagponal,calcareous
muds
Lagoon '! siliciclastic mu6s "~
/
,~ ~.... • •':.~.~.. -...~
Oolite shoal Offshore sediments FiS.19 - E x a m p l e of facies a s s e m b l a g e s and facies d i s t r i b u t i o n in the intermediate ramp (Dinantian platform: from Van Steenwinkel,1988:Fig.6.13).
28
in the same d e p o s i t i o n a l system; for e x a m p l e (1988) d e s c r i b e d a s i t u a t i o n w h e r e b e a c h e s are w i t h r e s p e c t to s a n d w a v e s (Fig.19).
Van Steenwinkel located landward
In the F l o r i d a p l a t f o r m the i n t e r m e d i a t e ramp is a c o m p l e x a r e a o c c u p i e d by a d i s c o n t i n u o u s alignment of n e a r s h o r e banks and small tidal deltas l o c a t e d c l o s e to the tidal inlets and to the t r a n s i t i o n from F l o r i d a Bay and the Gulf of M e x i c o (Fig.20). The d y n a m i c s of banks d e s c r i b e d by A i g n e r (1985) takes p l a c e by i n c r e m e n t s of s e d i m e n t v o l u m e s t r a n s p o r t e d by h u r r i c a n e s . The 'event' a c c r e t i o n d y n a m i c s leads to a l a n d w a r d t r a n s i t i o n from beaches and shell islands,to skeletal banks and mud banks (Aigner,1985: F i g . 1 8 ) . T h e w i n d w a r d side of lobes and s u b a q u e o u s dunes is e n r i c h e d in shells; b i o o l a s t b e a c h e s may form on t h e i r top; the l e e w a r d side c o n v e r s e l y is m u d d i e r in c o m p o s i t i o n . O n s h o r e s t o r m floods also p r o d u c e s p i l l o v e r lobes (Bali,1967), A s i t u a t i o n s i m i l a r to that d e s c r i b e d by A i g n e r (1985) from Florida Bay occurs in the Devonian platform (Carnic Alps, Italy) w h e r e s h o r e f a c e bars, s t o r m bars and b e a c h bars r e s u l t e d
SKELEB TA~L ~~'~a~~ ~ ~ 0
1
F i g , 2 0 - S k e l e t a l banks of F l o r i d a Bay, ramp (from G i n s b u r g , R . N . , w i t h p e r m i s s i o n ) .
in
2Krn
.~,"
LAND
the
intermediate
29
from the p i l i n g up of shells in a s t r a n d l i n e e n v i r o n m e n t . The c o m p o s i t i o n of the b e a c h was built up by s t e p w i s e a s s e m b l a g e s of sand b o d i e s of d i f f e r e n t p r o v e n a n c e , such as open lagoons and reef flats (Galii,1986; Fig.21). Open l a g o o n s are a s s o c i a t e d w i t h s a n d w a v e s and bars located in the i n t e r m e d i a t e ramp. T h e y are c o n s t i t u t e d by skeletal sands and p o p u l a t e d by thin- and t h i c k - s h e l l e d mollusks, o t h e r than g a s t r o p o d s , c r i n o i d s , f o r a m i n i f e r s and corals. The open lagoon facies are g e n e r a l l y transitional to the shallow ramp and located at both l a n d w a r d and s e a w a r d sides of s a n d w a v e bodies. More sheltered areas are b i o t u r b a t e d . Open lagoons located s e a w a r d are the sites of f o r m a t i o n of m - t h i c k bars, whereas those l o c a t e d t o w a r d s the s h a l l o w ramp, on the other side of the barrier, more c o m m o n l y d i s p l a y f i n i n g - u p w a r d s e q u e n c e s and b i o c l a s t lags t r a n s i t i o n a l to those of the s h a l l o w ramp. In the B a h a m a s s k e l e t a l sands are less than 2 km wide; they are w i d e r (iO km) a l o n g the n o r t h e r n m a r g i n and e x t e n d from the u p p e r s l o p e a c r o s s the o u t e r m a r g i n to w a t e r depths of about I0 m. T h e y t e r m i n a t e a b r u p t l y a g a i n s t cold sands and islands. In the J u r a s s i c 'Calcari Grigi' F o r m a t i o n the main l i t h o f a c i e s of the i n t e r m e d i a t e ramp are c o n s t i t u t e d by o o l i t e g r a i n s t o n e s and packstones, and skeletal wackestones, with subordinate amounts of nodular wackestones and mudstones. Here the intermediate ramp is d o m i n a t e d by o o l i t e sandwaves, such as that e x e m p l i f i e d in Fig,22: the sect.ion may be d i v i d e d into a lower and an u p p e r member. The basal m e m b e r is a p o o r l y s o r t e d l i t h o f a c i e s w i t h s u r f i c i a l o o l i t e s and lumps and an a d m i x t u r e of s k e l e t a l g r a i n s w h i c h c o n s t i t u t e the nuclei of the colds, intraclasts, p e l o i d s and c o a t e d grains. The u p p e r l i t h o f a c i e s is a well s o r t e d g r a i n s t o n e with t a n g e n t i a l colds, S e d i m e n t a r y structures are m a s s i v e bedding at the base, hummocky-cross b e d d i n g in the m i d d l e and wide, c r o s s - b e d d e d shallow channel fills r e m i n i s c e n t of the s w a l e y cross s t r a t i f i c a t i o n (Leckie and W a l k e r , 1 9 8 2 ) at the top. I n d i v i d u a l f i n i n g - u p w a r d s e q u e n c e s w i t h i n h u m m o c k y c r o s s - b e d d e d sets c o n t a i n internal s e q u e n c e s of structures comparable to the 'b-c-d' Bouma sequence: planar lamination (Walker,at ai.,1983) v e r t i c a l l y g r a d i n g to t r o u g h cross lamination with normal graded sets (of. Dott and Bourgeois,1982). The basal m a s s i v e bedded oolite grainstones and p a c k s t o n e s are i n t e r p r e t e d as shoals and s a n d w a v e s s i t u a t e d in a s t o r m - d o m i n a t e d area, at a s h a l l o w w a t e r depth. Ooid sand m i g r a t i o n took p l a c e u n d e r the influence of storms, Van Steenwinkel (1988) interpreted similar 'oolitic lump facies' f r o m a C a r b o n i f e r o u s ramp in B e l g i u m as a t r a n s g r e s s i v e
30
-,(--- Deep
Intermediate
ramp
Submerged sketetal bars
hwI
Emergent bars
ramp
Ridge
- - Sha{|ow
ramp
Pond
....................................................................................................................................................................................................................
".%
-% Well sorted grainstone
Mudstone 2Mudstone
3 , b ' 6 :'6-
1
,,~,'.-q~
Brachiopod coquina 2
8rachiopod coquina
Skeletal wackestone m 0
,~'~*.~,.o~: •
Poorly sorted skeletal ,int raclast packstone
,, ',¢e~o~,-
Mudstone 1
mO
Fig.21 B a t h y m e t tic profile intermediate ramp occurring platform, Italy ( G a l i i , 1 9 8 6 ) .
Skeleta! wackestone
and facies types in the Devonian
Mudstone
of the carbonate
lag d e p o s i t f o r m e d d u r i n g an i n c i p i e n t d r o w n i n g . B r i e f e p i s o d e s of bottom agitation alternated with longer, quiet periods c h a r a c t e r i z e d by a s l o w s e d i m e n t a t i o n rate, She c o m p a r e d s u c h grapestone lumps w i t h the g r a p e s t o n e lumps o c c u r r i n g at L i l y B a n k (little B a h a m a Bank) and at Cat Cay P l a t f o r m (Great B a h a m a Bank) where oolitically coated sands migrated landward in r e s p o n s e to an i n c r e a s e in the s e a - l e v e l rise and s u b s e q u e n t l y b e c a m e i n a c t i v e and the site of s e a - g r a s s g r o w t h and g r a p e s t o n e f o r m a t i o n . M i g r a t i o n takes p l a c e m a i n l y d u r i n g large s t o r m s and hurricanes. Oolitic sand shoals are common along the edges of s e v e r a l B a h a m a areas (Cat I s l a n d p l a t f o r m , J o u l t e r s Cay, B e r r y Islands, and so on). T h e y o c c u r as a c t i v e c o l d s h o a l s m a r g i n a l to the o p e n sea, and as s t a b i l i z e d b l a n k e t s h e e t s of o o l i t e sand flats w h i c h are g r a d a t i o n a l with other platform sediments (Multer, 1977). S k e l e t a l a d m i x t u r e s are g r e a t e s t in d e e p e r w a t e r areas. M o d e r n o o l i t e s a n d w a v e s m i g r a t e l a n d w a r d in r e s p o n s e to a s l o w s e a - l e v e l rise. S u b a q u e o u s d u n e s are e l o n g a t e d p a r a l l e l to the
31 4'.'o'~ ~ ' 6 ~D~
o oo
~ o
• ~ G 0 © u ' .© ©. / o
• o...
o '0'
J!:."?..o..o ; o." "oo
e e
.
.
.
".."
.. .o.
.Ovo •
'.
''
'o
o
~"
~ : -'.) j~;o.o°-: "
Oolitic grainstone
Mudstone Oncolite packstone
Oolitic lump facies
m
Fig.22 - Oolitic Formation,Venetian
v
sequence occurring Alps ( s e c t i o n #22).
in
the
'Calcari
direction of p r e v a i l i n g currents. Active shoals i n a c t i v e m i x e d o o l i t e facies and b e c o m e s t a b i l i z e d growth.
Grigi'
overlie the by s e a - g r a s s
Deep ramp The deep ramp is a deep lagoon; the lagoonal floor, located 5 to 15 as m u c h as 20 m b e l o w wave base, is t y p i c a l l y p o p u l a t e d by o l i g o t y p i c , h i g h - d e n s i t y and l o w - d i v e r s i t y mollusks. B i v a l v e s form t i g h t l y packed accumulations embedded in a w a c k e s t o n e
32
{0
o
•
r.) ..o ~1
~
,~
~
o-- "o
.~, 0
"0
•,~, "~ ',4 ::~: (~ o P-, ..c: .~ •,'.I
4.~
,.~ ..~ ~ ,~ ~
r"
,~ ~
,el
o~ 0
QJ
~°~ ~.o,o oOH ~
N
~
0
• .~ 0
~ ,~
o
~~.~
..o ~
o
~
o
"o ~
,~
0
.~ ~ , ,,,-4 ' ~
~
o ~
o
o~ ~.-~~ ~.~~ 0
-
m
0
4.~
,.~
(11 ' ' t
'~
~
03 ~
~
0
33
matrix (Fig.23A,B,C). Mudstones alternate with fossiliferous wackestones. These fossils and o r g a n i s m s are also found in other sectors of the ramp, but they do not form big v o l u m e s of sediment as in the deep ramp; here they b e c o m e a r r a n g e d as c a t c h - u p reefs, b i o s t r o m e s and banks r e a c h i n g 3 as much as 7 9 m in t h i c k n e s s (Fig.23 D,E). Walkden and Gutteridge (198~,1987) and Gutteridge (1987) described different styles of mud mounds from the late B r i g a n t i a n Eyam L i m e s t o n e in the D e r b y s h i r e c a r b o n a t e p l a t f o r m (Fig.2~). The mounding styles (tabular dome-shaped l a t e r a l l y and v e r t i c a l l y a c c r e t e d mounds) were d e t e r m i n e d by the w a t e r depth of d e p o s i t i o n . Laterally accreted mounds are u s u a l l y found in the s h a l l o w ramp, w h e r e a s v e r t i c a l l y a c o r e t e d mounds occur in the deep ramp. In c o n t r a s t to the laterally a c c r e t e d mounds, flank facies of v e r t i c a l l y a c c r e t e d m o u n d s are poorly developed;the s e d i m e n t s u r r o u n d i n g bases of v e r t i c a l l y a c c r e t e d mounds d i s p l a y some cross b e d d i n g e v i d e n c i n g for an initial shallow water of deposition. The core, composed of peloidal mud, does not show any z o n a t i o n w h i c h rules out a c h a n g e in the w a t e r d e p t h t h r o u g h o u t d e p o s i t i o n , except at the very top, where v a d o s e d i a g e n e t i c features point to p e r i o d s of subaerial exposure. A n a l o g o u s bank styles o c c u r in the J u r a s s i c s h a l l o w ramp in the V e n e t i a n Alps (Fig.2~). Small mounds, 1 m thick to 5 m wide, together with multiply truncation scours infilled with L i t h i o t i s shells, occur in the s h a l l o w ramp. Banks o c c u r r i n g as s t e e p l y inclined, s i g m o i d a l to u n d u l a t i n g beds, may c o r r e s p o n d to the flank facies of l a t e r a l l y accreted Lithiotis banks d e v e l o p e d close to the i n t e r m e d i a t e ramp. The g r o w t h of t h i c k L i t h i o t i s banks o c c u r r e d in deeper, subsiding areas of the lagoon, as is s u g g e s t e d by the lack of m e c h a n i c a l structures within banks, a h i g h faunal density, uniformity, large, 'in situ' shell sizes, and o c c u r r e n c e of cross b e d d i n g only at the base and top of the banks (Fig.23). The L i t h i o t i s banks were i n t e r p r e t e d by B o s e l l i n i (1972) to h a v e been d e p o s i t e d w i t h i n a system of m i g r a t i n g tidal p o i n t bars (Fig.25). Accord.ing to that i n t e r p r e t a t i o n , B-type mounds formed at the b o t t o m of point bars, C and D - t y p e m o u n d s w e r e i n t e r p r e t e d as point bars or as m e c h a n i c a l d e p o s i t s formed in the bends of m e a n d e r i n g c h a n n e l s or b e t w e e n larger c h a n n e l s . T h e model put forth by B o s e l l i n i (1972) is w r o n g (of. W r i g h t , 1 9 8 A ; Galli,1990).Nevertheless, his p r o f i l e of point bars may be taken as the p r o f i l e of an i n t r a s h e l f ramp: hence, B-type mounds formed in the deep ramp; C,D, E types d e v e l o p e d in the i n t e r m e d i a t e ramp, w h e r e a s c h a n n e l s and scours were p r o d u c e d in the s h a l l o w ramp.
34
TABULAR
MOUND
5m
•
Sm
\ \
LATERALLY ACCRETED
, '
VERTICALLY~ ACCRETED "
[~.m 100 m
'
~
r ~
~Om
1
SHALLOW RAMP
lateral accretion
INTERMEDIATE RAMP
vertical accretion DEEP RAMP
Fig.24 EnEland
Top : mud mounds in t h e A s b i a n - B r i g a n t i a n (Walkden and GutteridEe,1987). Bottom: Lithiotis banks.
platform, types of
35
A
B
lO -20. m
C /II 1 /
:
x
//// I
,,
I
,, / ,, ,,
D
I x_ I
20-30 m - -
\
X,
~
\,,,,,
,\
4-5~ I ,:1",l' .... "",",w,' " ',' '",~",'q~P
I
\\
20-40 rn .............................. D-.E.. . ..
A
. . . . . . . . . . . . . . .
y~ , . . . .
X \
X
/'""',
Y ~ D-E . .
C
-
-B ~
D-E Y
Fig.25 - Paleoenvironmental model of Bosellini (1972), He mistakenly interpreted Lithiotis b a n k s to h a v e f o r m e d w i t h i n a s y s t e m of m i g r a t i n g t i d a l p o i n t bars. H o w e v e r , t i d a l facies are absent in the s t u d y a r e a a n d t h e r e is n o t m u c h e v i d e n c e for migration of t i d a l c h a n n e l s in m o d e r n c a r b o n a t e environments. T h e m o d e l is s t i l l a p p l i c a b l e if the p r o f i l e of the 'point bar' is c o n s i d e r e d to be the p r o f i l e of an i n t r a s h e l f ramp.
The Jurassic intrashelf ramp occurring in the 'Calcari Grigi' F o r m a t i o n w a s s u b j e c t e d to a s t r o n g e p i s o d i c hydraulic action (Galli,1990). Channel morphologies reflect the former depth (Fig.26).Undulating bedforms and flattened,wide channel o u t l i n e s o c c u r in t h e d e e p ramp. D e e p l y i n c i s e d , t i g h t e r channel outlines cutting shoals are commonly found in t h e shallow ramp. The distribution of the t y p e s of c h a n n e l o u t l i n e s o c c u r r i n g in the study area of the 'Calcari Grigi' Formation (Fig.26) follows the variations in bathymetry of the ramp. Within shallowing-upward sequences, wide channels o c c u r at the b a s e (Fig.26:A), whereas semicircular s c o u r s a r e f o u n d t o w a r d s ithe top (Fig.26:B), T h i s is a l s o a p p a r e n t f r o m a n e x a m i n a t i o n of v e r t i c a l s e q u e n c e s of c h a n n e l m o r p h o l o s i e s (Fig.27).
36
R:H • 2 ~
"
f
SHALLOWRAMP
R:H= 3 ~
R:H=4
B R:H = n
DEEP RAMP
B
,..
//
~
. . • .....
.........
•
0
. A
..:i: {!i~i" B
B
jA
5KM.
SHALLOW
DEEP
RAMP
RAMP.
N
37
NW
SE
~am=ms~ssE:mmcml
0
lOre.
F i g . 2 7 - U p w a r d c h a n g e s in c h a n n e l m o r p h o l o g i e s from u n d u l a t e d to e l l i p t i c a l reflect a s h a l l o w i n g upward trend,confirmed by vertical changes in l i t h o f a c i e s ('Calcari Grigi' Formation: s e c t i o n #27). Banks o c c u r r i n g in the deep ramp are a n a l o g o u s to a n u m b e r of 'catch-up' reefs d e s c r i b e d in the l i t e r a t u r e (Fig.28), as is i n d i c a t e d by the v e r t i c a l d e c r e a s e in size of fossils and an increase in the p r o p o r t i o n of lithoclasts. The u p p e r m o s t p a r t s contain fossils more indicative for a shallower setting, scours, channels and w a v e - g e n e r a t e d structures reflecting a d e p o s i t i o n a b o v e w a v e b a s e . T r e n d s d i s p l a y e d by these s e q u e n c e s record transitions from deep, quiet water stages, to a shallower,agitated w a t e r stage that c o r r e s p o n d s to v a r i a t i o n s in the steepness of the curve of change in sea-level. Initially, the space a v a i l a b l e for s e d i m e n t a t i o n was i n f i l l e d by a mechanism of vertical sediment growth (vertical aggradation); later, by lateral m i g r a t i o n ( p r o g r a d a t i o n ) , once the s e d i m e n t a r y i n t e r f a c e c a u g h t - u p with the sea-level. In the F l o r i d a p l a t f o r m the deep ramp, described by P e r k i n s (1977), consists of a landward area characterized by a semirestricted water circulation, and a s e a w a r d area, where c i r c u l a t i o n is more limited. The c o m p o s i t i o n and g r a i n size of the s e a w a r d m o s t side of the deep ramp r e f l e c t s the p r o x i m i t y to the reefs. Sediments become finer and of more varied composition towards the i n t e r m e d i a t e ramp w h e r e the i n c l i n e d
F i g . 2 6 - A : V a r i a t i o n s of e l l i p t i c i t y of c h a n n e l o u t l i n e s as a f u n c t i o n of the h e i g h t : a m p l i t u d e (H:R) ratios with depth. B: schematic representation of the outlines of channels and scours, in the s t u d y area of the 'Calcari Grigi' F o r m a t i o n , r e l a t e d to the r e c o n s t r u c t e d bathymetry, Circular scours are m a i n l y c o n f i n e d to the s h a l l o w ramp; flattened channels occur p r e f e r e n t i a l l y in the o t h e r sectors.
38 BRITOMART REEF 041
.r.~.~ •
48-
..,..
10~
•3 ,,2
31 122l
E 16r~ 2o-
2 0 ~ •1
2428-
32 O5-
ALACRAN REEF
10,~~--~
t0-
Years B.P. (x 1ooo) 31
21
E
;15-
2
t•
25
~:~ :l~ Cor~ rubble 0
300
2 3 4 5 6 7 8910 Years B,P. {x ~ooa}-
GALETA POINT REEF 0mO r-~o~:~.--..~..t ==6 •
.
=15
5_
.
4l 3•
1 3
tO
I5
~
12 It
a
2• 15-
20, 0
Years B.P. (xloOO)
39 surface is covered by patch reefs and poorly sorted, bioturbated wackestone banks. These form a compound, elongated, disoontinuous w e d g e p a r a l l e l to the e d g e of t h e p l a t f o r m . T h e y are also asymmetric, w i t h the s t e e p e s t side located landward. Inner structures c l o s e to the i n t e r m e d i a t e ramp consist of acoretionary sets inclined at a low a n g l e (I ° - 5 ° ) a n d s t r i k i n g p a r a l l e l to the e d g e of the p l a t f o r m (Enos,1977).They m a y be a m o d e r n a n a l o g u e of a n c i e n t , inclined beds connecting the intermediate and deep ramp (Fig.29).
PUEBLO NUEVO REEF WABASH
REEF
40
i'i~!. .'.-.",|. ;,.e ..
Massive corals and corallinae algae
....~;-<j
Ma s save hemispherical Favositldae (packstone} 3O
),.".: ii '
"
. ~ 3
Massive coralsand robust branching coral~
~/.:1 Fragile tabulate,mainly Syringopora ( wacke tone)
20 - " . ' ~
10 . . . . .
? ? mO
"-i :.".".!
0
Fragile branching corals
Cora nae algae
?):;:~::]
Fig.28 - Examples of 'catch-up' reefs. Britomart Reef,Great B a r r i e r R e e f : J o h n s o n , et a l . ( 1 9 8 A ) 9 G a l e t a P o i n t Reef, P a n a m a : MacIntyre and Glynn (1976);Alacran Reef, Isla Perez,Mexioo: MacIntyre, et ai.(1977); Wabash Reef,Devonian, Indiana: Lowenstam (1950); Pueblo Nuevo Reef,Oligocene, Mexico: Frost (1977). T h e s t r a t i g r a p h y a n d e v o l u t i o n of the H o l o c e n e e x a m p l e s shows a strict dependance u p o n the r e l a t i v e s e a - l e v e l c u r v e . A s i m i l a r o o n t r o l is i n f e r r e d for the o l d e r e x a m p l e s .
40
--
W
-
OJ
O~
cO F-, -~ 0".
,.~ bO
,--I .--4
v
w l-.i
o
M
~.~
~g'~ .,..~
~
~ >. 5 • -
.0,4
>, •
0
"o
"0
.1~ 0
.1=
.,-I
-
/ ~
~ '"~
.,~, .i,~
0
~ 0 cO r-~ W ,-,4
cO • ~ .~ "0
.
~0
0.I
~,,~
I~
g
~.~
"
×
~
JT"" • I
.,-i
-
"'0
0
"13
Geometries
of
intrashelf
ramps
I n t r a s h e l f ramp g e o m e t r i e s fall into two f u n d a m e n t a l c a t e g o r i e s (Fig.30) which correspond respectively to divergent and c o n v e r g e n t p a t t e r n s d e s c r i b e d further below: I) onlap ramps; 2) o f f l a p ramps The r e c o g n i t i o n of these two a r c h i t e c t u r e s was a t t e n d a n t on the application of 'event' correlation between stratigraphic sections and logs (Ager,1981; Dixon,et aI.,1981~ Matthews, 198~;Aigner,1985).The use of p h y s i c a l bodies and s t r a t i g r a p h i c horizons as chronostratigraphic tools within shallow-water carbonate platforms offers a better strati~raphic resolution than b i o s t r a t i g r a p h i c criteria because the time interval of f o r m a t i o n of p h y s i c a l m a r k e r s such as storm d e p o s i t s is s h o r t e r than the rate of e v o l u t i o n of s h a l l o w - w a t e r o r g a n i s m s living in a platform (Sommerville,1979).
ONLAPRAMPI OFFLAPRAMPE Fig.30 - Geometries of intrashelf ramps.The onlap ramp is g e n e r a l l y d e v e l o p e d b e l o w the o f f l a p ramp and is b o u n d e d by flooding surfaces, therefore corresponding to a genetic stratigraphio sequence (Galloway,1989).
0nlap
~eometry
The o n l a p geometry is c o n s t i t u t e d by a 20 + 60 m thick, divergent prism. Isochronous lines c o n v e r g e towards a hinge zone. As a result, facies and cycles thin towards the hinge. Facies associations in the hinge zone c o m p r i s e shallow ramp facies a s s o c i a t i o n s (thin- and t h i c k - b e d d e d a l t e r n a t i o n s ) . The i n f l e c t i o n in the topographic profile, w h i c h is the site of
42
FLEXURE
TROUGH
HINGE
DEEP RAMP
INTERMEDIATE RAMP
SHALLOW
RAMP
Banks, biostromes
Sandwaves, beaches
T hick-, thin ' bedded alternations Y "-~ :-~'.5, "C
" f'.''~
~..-~ ":--L^ ".' o r 0 7
~
_
%
] !Z
FORMATION A
T
E
~
!
-" I;Z
45
~
DISCONFORMITY ,
.| J
_
_ ~
_
(~(,~ ~,~(~
-CO :~
IL..
; ' . . . " :'." •
Fossiferous grainstones and wackestones with molluscs,algae, echinoids. oncolites
.:.-::
.9. I ~ nI,i, , ~ /
~ Structures of subaerial ~ / exposure.
C
~ ~ -
I
z- l --
Algal mats, mud-cracks fenestrae, restricted fauna.
Basal conglomerate. DISCONFORMITY
1 rn
~
~ ~k.)
Fig.32 - Deepening-upward sequences analogous to the hinge sequence.A: Example of hinge sequence (Devonian platform, Carnic Alps) consisting of thick-bedded alternations (intraelast grainstones/packstones passing to ostracodc a l c i s p h e r e - Amphipora m u d s t o n e s w h i c h are o v e r l a i n by a t h i c k Amphipora (deep lagoon). B: D e e p e n i n g bank c o n t a i n i n g a b u n d a n t - upward s e q u e n c e from the E n g l i s h Z e a h s t e i n (New M i c k l e f i e l d Quarry) c o n s i s t i n g of intertidal flat facies ("Hampole Beds") o v e r l a i n by cold s a n d w a v e s c h a r a c t e r i z e d by h o r i z o n t a l l y b e d d e d g r a i n s t o n e s at the base and large scale b e d d i n g i n c r e a s i n g in size u p w a r d s . ( T h e sketch b e l o w is from Smith, et ai.,1986). C : L o f e r c y c l o t h e m (Fischer,1966).
46
depends, a m o n g variations.
other
factors,
of
the
rapidity
of
the
sea-level
A h i n g e s e q u e n c e m a y c o r r e s p o n d to the l a n d w a r d m o s t t e r m i n a t i o n of clinoforms within carbonate platforms and marks the separation or d i s c o n t i n u i t y between wedges within carbonate prisms. An e x a m p l e of such a d i s c o n t i n u i t y resembling a hinge s e q u e n c e is the " H a m p o l e beds" d e s c r i b e d by Smith, et a i . ( 1 9 8 6 ) from the E n g l i s h Z e c h s t e i n (Fig.32). A trouEh sequence is an alternation of deep ramp and intermediate ramp facies associations (Fig.31). A long-term deepening-upward t r e n d e x p e r i e n c e d by a p l a t f o r m leads to the d e p o s i t i o n of a t r o u g h s e q u e n c e o v e r the h i n g e sequence,
Offlap
geometry
The o f f l a p g e o m e t r y is a s e d i m e n t a r y prism, of the type s h o w n in F i g . 3 0 , T h e s h a l l o w ramp zone is the t h i c k e s t s e c t o r of the o f f l a p ramp g e o m e t r y . The i n f l e c t i o n in the t o p o g r a p h i c p r o f i l e is the flexure. The deep ramp c o i n c i d e s w i t h the trough zone. Time lines c o n v e r g e t o w a r d s the h i n g e w h i c h is l o c a t e d in the deep ramp. E x a m p l e s of this type of i n t r a s h e l f ramp g e o m e t r y i n c l u d e the i n t r a s h e l f ramp o c c u r r i n g in the D e r b y s h i r e c a r b o n a t e p l a t f o r m (Walkden,1982;Fig.33) and the P l e i s t o c e n e in the Great B a h a m a B a n k s t u d i e d by B e a c h (1982) and B e a c h & G i n s b u r g (1980), s h o w n in Fig.3~. The f o r m a t i o n of an o f f l a p g e o m e t r y is d e t e r m i n e d l a r g e l y by autocyclic,progradational p r o c e s s e s and e u s t a t i c v a r i a t i o n s . In an offlap geometry deep ramp facies are developed over p r o g r e s s i v e l y n a r r o w a r e a s ,from b o t t o m to top of s t r a t i g r a p h i c sections, w i t h the p r o d u c t i o n of s h a l l o w i n g and c o a r s e n i n g upward sequences and megasequences,Upward faunal variations reflect changes from open to semirestricted environments. Tectonic subsidence is not an essential control in the f o r m a t i o n of o f f l a p s t r u c t u r e s } n e v e r t h e l e s s , the a c t i o n of a r o t a t i o n a l s u b s i d e n c e a r o u n d the h i n g e l o c a t e d in the d e e p ramp is not e x c l u d e d . Short-term sea-level changes (I0~-I05 years) tuned in the M i l a n k o v i t o h band are e s p e c i a l l y a p p a r e n t in the s h a l l o w - r a m p zone; a tidal flat may form in the s h a l l o w e s t areas of the
47
I
:1 I I ~( tll i I i t t t k. i I Jl)t I I I , J , il~lcLI
J
tj ,
NW
j~ ~
BASNS
~q~/--
ll/lI ~%k
/
,.
'l
t
t%ll
Fis,33 - O f f l a p ramp (Asbian - B r i g a n t i a n p l a t f o r m , D e r b y s h i r e , EnEland), I: massive-bedded Erainstones and packstones; 2: medium-bedded grey packstones and w a c k e s t o n e s ; 3: g r a i n s t o n e shoals; A: t h i n - b e d d e d d a r k s h a l e y w a c k e s t o n e s and m u d s t o n e s ; 5: knoll reef and marEinal reef; 6: lava horizon (from Walkden,1982: riEht~ and G u t t e r i d E e , 1 9 8 7 : left), s h a l l o w ramp; the deep ramp records the a c t i o n of s t o r m s , A study on s t o r m p r o c e s s e s in an ancient, o f f l a p ramp o c c u r r i n g in the D ~ r r e n s t e i n F o r m a t i o n , D o l o m i t e s (Galii,1989) s h o w e d that p r o x i m a l i t y trends are a n a l o g o u s to those d e s c r i b e d by A i g n e r (1985): they are o p p o s i t e to those r e c o r d e d in the o n l a p ramp g e o m e t r i e s (see above), WEST
30--
~
EAST
.........................
--~
45-/
m 60-
F i g , 3 ~ - O f f l a p ramp and G i n s b u r g , 1 9 8 0 )
(dotted
area)
in
the
Bahama
Bank
(Beach
48
The D ~ r r e n s t e i n Formation (Triassic, eastern Dolomites) was m i s t a k e n l y i n t e r p r e t e d by B o s e l l i n i (198A) to be a p r o d u c t of vertical sediment aggradation o c c u r r e d d u r i n g a s t i l l s t a n d of the s e a - l e v e l and a b s e n c e of d i f f e r e n t i a l subsidence. Rather than a v e r t i c a l sediment aggradation, a stil[stand of the sea-level is more likely to p r o d u c e a lateral progradation (Kendall & S c h l a g e r , 1 9 8 1 ) . Furthermore, there s no e v i d e n c e for a s t i l l s t a n d of the s e a - l e v e l in the C a r n i a n , a s result from an e x a m i n a t i o n of the e u s t a t i c c u r v e by Haq, et a i . ( 1 9 8 7 ) , w h i c h shows a f i r s t - o r d e r s l o w s e a - l e v e l rise. The depositional model, illustrated in Fig.35 (Galii,1989; Bonaga, et a i . , 1 9 8 9 ) , suggests that s e d i m e n t a t i o n took p l a c e m a i n l y by p r o g r a d a t i o n . The modal c y c l e (Fig. B5) d i s p l a y s o p p o s i t e t r e n d s w i t h r e s p e c t to the h i n E e s e q u e n c e of the o n l a p ramp, where shallow-ramp l i t h o f a c i e s u n d e r l i e the b i o s t r o m e s and b a n k s of the deep ramp. It c o n s i s t s of a c o m p o u n d s h a l l o w i n E - u p w a r d sequence composed of a f i n i n g - and t h i n n i n g - u p w a r d sequence, d e p o s i t e d b e l o w w a v e base, in the deep ramp, overlain by a coarsening-upward s e q u e n c e d e p o s i t e d a b o v e w a v e base, in the s h a l l o w - r a m p z o n e . A consequence of the lateral progradation, which is the m a i n process operating in the o f f l a p ramp, was the formation of shallowing-upward meEasequences,the shallow-ramp lithofacies and s e q u e n c e s o v e r l y i n g the deep ramp l i t h o f a c i e s .
49
Grainstone / packstone with intraclasts and oncolites
T SHALLOW RAMP
Packstone/grainstone with intraclasts
%/
Packstone with peloids
" "" . ' ,
".'2 ,
°
6-
•
,
,
~."
Grainstone/packstone with bioclasts and peloi ds
.~. " - " "N"
.
~.
•
""~"
:-5. - 6 •
DEEP RAMP
c ...:)
"
mi
PROGRADATION
•
~%~ .................. . ~ .........~ ......~ .....~ ..... \ \
:,,. ::~.
'
-~
~.~.
~
..~f.!
M.G/R
......
~
I,GIR
V
,~.
M.GIR
50
O O
40-
•
30
/
® ~IN~
~,,uoo
3 0 - -
J
Km 0
Pelmo
a
30
®
20
20
lO
lO I 10~ il 10
2O
~
.
.
.
.
.
.
.
o. o . o o o
~2 m o I
I
mo
M G/P
Fig.35 - Stratigraphic sections,modal c y c l e and d e p o s i t i o n a l model of the D ~ r r e n s t e i n F o r m a t i o n , D o l o m i t e s . I: S h a l l o w ramp facies a s s o c i a t i o n s ; 2: d e e p ramp facies (from G a l i i , 1 9 8 9 and Bonaga, et a l . , 1 9 8 9 ) . I n the study area the deposition took place by lateral p r o g r a d a t i o n .
Sequence stratigraphy
The sequence stratigraphy depositional model by Vail,et ai.(1977;1984) s h o w i n g d e p o s i t i o n a l s e q u e n c e s and facies tracts is shown in Fi8.36. maximum flooding surface type-2 sequence boundary
transgressive surface type-1 sequence boundary
Condensed section ~ ~
Sequence boundary
HST
--.
/ ~
TST
Transgressivesurface / ~
* - Seaward
~
LST Sequence boundary
Landward --,.
*-- Low
Coastal onlap Fig.36 - Depositional sequence (from Swift,et p a s s i v e m a r g i n model (from V a i i , 1 9 8 ~ 1 9 8 7 ) .
High --~ Sealevel ai.,1987)
and
52
A depositional sequence is d e f i n e d as a s u c c e s s i o n of facies tracts f o r m e d in r e s p o n s e to a r e l a t i v e s e a l e v e l cycle. It is a succession of'conformable, genetically-related strata, b o u n d e d below and above by unconformities and their correlative conformities ( V a i l , e t a i . , 1 9 7 7 ) . A facies tract is "a l i n k a g e of c o n t e m p o r a n e o u s d e p o s i t i o n a l s y s t e m s (Brown & F i s c h e r , 1 9 7 7 ) , each linked to a s p e c i f i c segment of the eustatic curve".A depositional s e q u e n c e is any s t r a t i g r a p h i c unit, from a few m to 1000 m thick, with vertical boundaries constituted by physical surfaces corresponding to t e m p o r a l d i s c o n t i n u i t i e s in the s e d i m e n t a t i o n . The unit c o m p r i s e d b e t w e e n these s u r f a c e s is a g e n e t i c a l l y h o m o g e n e o u s body. There are v a r i o u s gerarchic types of d e p o s i t i o n a l sequences which are the product of distinct orders of geological phenomena. Generally, depositional sequences are sigmoidal b o d i e s f o r m e d by d e p o s i t i o n a l systems and f o r m a t i o n s passing from the sea to the land from b a s i n a l , slope, p l a t f o r m , p a r a l i c and c o n t i n e n t a l settings. Although difficult to define, owing to the d e t a i l e d a n a l y s i s and c o r r e l a t i o n s required for t h e i r identification, depositional sequences are true n a t u r a l u n i t s which record natural geological processes, such as transgressions, r e g r e s s i o n s and r e l a t i v e s e a l e v e l changes. The d e p o s i t i o n a l s e q u e n c e s d e s c r i b e d h e r e f o r m e d on a t h e r m a l l y s u b s i d i n g margin. The h i n g e is l o c a t e d l a n d w a r d of the a r e a of sedimentation. Their facies distribution and sedimentary pattern are c o n t r o l l e d by the i n t e r a c t i o n of : l ) e u s t a t i c s e a l e v e l change; 2) subsidence~ 3) sedimentation rate and A) environmental changes (Schlager,1991).The space a v a i l a b l e for s e d i m e n t a t i o n is the r e l a t i v e c h a n g e in s e a - l e v e l w h i c h is a c o m b i n e d e f f e c t of e u s t a t i c s e a - l e v e l and s u b s i d e n c e . T h e r e may be a r e l a t i v e fall, stillstand or rise of the sea-level resulting from different combinations of sea-level fall, rise, stillstand, s u b s i d e n c e and t e c t o n i c u p l i f t (Van S t e e n w i n k e l , 1 9 8 8 ) . The rate of r e l a t i v e c h a n g e of s e a l e v e l is a d e r i v a t i v e f u n c t i o n of the e u s t a t i c s e a - l e v e l c u r v e (Fig.37) : it is the rate of a d d i t i o n or subtraction of the space available for sedimentation (Posamentier,et The
most
ai.,1988).
important
changes
in s e d i m e n t a t i o n
take
place
when
the
rate of s e a l e v e l rise or fall are h i g h e s t . Subaerial unconformities are p r o d u c e d w h e n the space a v a i l a b l e for s e d i m e n t a t i o n is taken away; they o c c u r as a result of a rapid s e a - l e v e l fall. They form s e q u e n c e b o u n d a r i e s . A type-1 sequence boundary is " c h a r a c t e r i z e d by a s u b a e r i a l
53
exposure and concurrent subaerial erosion, associated with stream rejuvenation (incised valleys), a basinward shift of facies, a landward shift in c o a s t a l onlap, and onlap of overlying strata" (Vaii,1987). It is accompanied by the d e v e l o p m e n t of a l o w s t a n d facies tract (Haq,et ai.,1987). A slower rate of s e a l e v e l fall, less than or equal the rate of basin s u b s i d e n c e at the p l a t f o r m margin, produces a type-2 s e q u e n c e boundary. "It is m a r k e d by s u b a e r i a l e x p o s u r e and a d o w n w a r d shift of c o a s t a l o n l a p l a n d w a r d of the d e p o s i t i o n a l s h o r e l i n e break, but lacks both s u b a e r i a l erosion associated with stream rejuvenation and basinward shift in facies" (Vaii,!987). In o t h e r words, the whole shelf may not be exposed. At a later stage, when the r e g i o n a l subsidence outrans the slowing rate of sealevel fall, new space available to s e d i m e n t a t i o n is c r e a t e d by the r e l a t i v e rise in s e a l e v e l and a p r o g r a d i n g l o w s t a n d wedge facies tract a c c u m u l a t e s b e t w e e n the shelf edge and the l o w s t a n d fan. Later, the lowstand wedge facies tract o v e r l i e s the l o w s t a n d fan. In a c a r b o n a t e s e t t i n g a fall in the s e a l e v e l d e t e r m i n e s non d e p o s i t i o n , s u b m a r i n e erosion, c e m e n t a t i o n and the f o r m a t i o n of lithoclast beds. The carbonate 'factory' ceases to work (Droxler & Schlager,1985). Falls of relative sealevel are associated with karst, soil development on the platform (Kendall and Schlager, 1981). A c c o r d i n g to Sarg (1988) l o w s t a n d facies tracts associated w i t h a type-i u n c o n f o r m i t y lead to s i g n i f i c a n t slope front e r o s i o n and s h e d d i n g of large v o l u m e s of c o a r s e talus into the b a s i n . L o w s t a n d s h e d d i n g is c o m m o n in s i l i c i c l a s t i c systems9 it s h o u l d be an e x c e p t i o n r a t h e r than a rule in c a r b o n a t e systems. In this w o r k it is p r o p o s e d that d e p o s i t i o n of m e g a b r e c c i a s (lowstand fan facies) at s p e c i f i c time i n t e r v a l s was triggered by global episodes of g e o i d a l deformation. A rapid relative sealevel rise determines a transgression, because the sedimentation rate is no longer sufficient to fill-up the space. A transgressive surface develops above a l o w s t a n d facies tract. W h e n l o w s t a n d d e p o s i t s are lacking, the transgressive surface coincides with a facies boundary (ravinement surface: Stamp,1922). The formation of a transgressive (retrogradational) facies tract takes p l a c e a l o n g the s t e e p e s t part of a r i s i n g sealevel curve. A condensed s e c t i o n is d e p o s i t e d s e a w a r d of the d e p o s i t i o n a l area b e c a u s e there the sedimentation rate is too low.Younger units are p r o g r e s s i v e l y t h i n n e r u p w a r d and b a s i n w a r d as a result of b a s i n starvation.
54
TIME
High t EUSTACY
Low
'I t"'-.J
SUBSIDENCE
'I
i
I
I I
I
I
,
,
'
I
~
I
l
Uplift 1 ~ I ~
, " - ~
I
Susidence I
RATE OF EUSTATIC CHANGE
l
Fall ~
I
I
Rise RATE OF SUBSIDENCE
t
I i I.
lI
Fall i
=
RATE OF RELATIVE SEA-LEVEL CHANGE
I I I I
I I ! I
-I I ! I
I I 1 I
I I 1 I
RATE OF ADDITION OF N E W SPACE
I
Rise O Fall~
Fig.37 - Relative sealevel as subsidence (from Posamentier,et
a function ai.,1988).
of
eustacy
and
T h e m a x i m u m f l o o d i n g s u r f a c e , or d o w n l a p s u r f a c e , s e p a r a t e s the transgressive f a c i e s t r a c t f r o m the o v e r l y i n g highstand facies tract. It m a r k s t h e m a x i m u m l a n d w a r d s h i f t of t h e t r a n s g r e s s i v e facies tract. As a r e s u l t of a g r a d u a l slowing of the relative sealevel rise,or generally during a decrease in t h e r a t e of r e l a t i v e c h a n g e in s e a l e v e l , there is a s l o w s u b t r a c t i o n of the s p a c e available to s e d i m e n t a t i o n a n d s e d i m e n t s a r e f o r c e d to a g g r a d e and prograde above the transgressive facies tract with the formation of a highstand facies tract. It is possible to distinguish an early aggradational, and a late progradational facies tract.The upper surface of the highstandfaoies tract m a y be a t y p e - 2 o r a t y p e - I s e q u e n c e b o u n d a r y , d e p e n d i n g of t h e r a p i d i t y o f the s e a l e v e l fall.
55
When a rapid s e a - l e v e l rise changes into a slow s e a - l e v e l fall, or a slow fall c h a n g e s into a slow rise: more g e n e r a l l y d u r i n g a m a x i m u m i n c r e a s e in the rate of r e l a t i v e c h a n g e of sea-level, the n e w l y added space is i n f i l l e d with an a g g r a d a t i o n a l progradational complex (shelf m a r g i n facies tract) above the h i g h s t a n d facies tract and a t y p e - 2 u n c o n f o r m i t y (Vaii,1987). This tract is c h a r a c t e r i z e d by stacked sequences with an i n c r e a s i n g d e e p e n i n g tendency; it r e p r e s e n t s the f i l l i n g - u p of t o p o g r a p h y b e f o r e drowning. It is o v e r l a i n by the t r a n s g r e s s i v e facies tract (Haq, et a i . , 1 9 8 7 ) . The r e l a t i v e sea-level is the e n d - p r o d u c t of two v a r i a b l e s : eustasy and subsidence. It is the space available for sedimentation (Posamentier,et ai.,1988). The rate of r e l a t i v e s e a - l e v e l c h a n g e r e s u l t s from the d i f f e r e n c e b e t w e e n rate of e u s t a t i c c h a n g e and the rate of subsidence: it is the rate of change of space available to sedimentation. It is a main controlling factor in the depositional pattern as is d e m o n s t r a t e d by Van S t e e n w i n k e l (1988).As shown above, across the curve of c h a n g e in the rate of the r e l a t i v e sea-level several tracts may by distinguished that correspond to increases or slowings of the sea-level change leading to r e g r e s s i v e or t r a n s g r e s s i v e p h a s e s . A c c o r d i n g to the t e r m i n o l o g y d e r i v e d from s e i s m i c s t r a t i g r a p h y (Haq,et ai.,1987), the facies tracts that form the d e p o s i t i o n a l sequences discussed in the case h i s t o r i e s d e s c r i b e d b e l o w are the following: I 2 3 A
-
t r a n s g r e s s i v e facies tract; shelf m a r g i n facies tract; h i g h s t a n d facies tract; l o w s t a n d facies tract.
Fig.38 summarizes as a reference the facies a s s o c i a t e d d i s c o n t i n u i t y surfaces, in r e l a t i o n to c h a n g e of the r e l a t i v e s e a - l e v e l .
Transgressive.
facies
tracts and the rate of
tract
D u r i n g this tract a rapid i n c r e a s e in the rate of the r e l a t i v e sea-level determines a drowning : sedimentation does not keep pace with the sea-level rise and 'is taken by surprise' (Kendall and S c h l a g e r , 1 9 8 1 ) . Either black micrites or p a p e r shales form d u r i n g this tract. Beds c o m p o s e d of f a s t - g r o w i n g , m o n o t y p i c e p i b e n t h i o faunal a s s e m b l a g e s may a l s o form, p r o v i d e d the organisms are c a p a b l e of keeping pace with the r i s i n g
56
LOWSTAND SYSTEM TRACT
HIGHSTAND
SYSTEM TRACT
I MAXIMUM FLOODING SURFACE ~ -
TRANSGRESSIVE
SYSTEM
TRACT
---•
TRANSGRESSIVE SURFACE
SHELF
MARGIN
SYSTEM
TRACT
RAVINEMENT
LOWSTAND
SURFACE
SYSTEM
I
TRACT
:
~...?. --%,:..
Fig,48 - Core profiles freshwater lithofacies,
showing
alternations
between
marine
and
82
.~
MIAMI OOLITE SEQUENCE BOUNDARY
!:~ "'"
SEQUENCE"C"
~..~: ,==4sSEOUENCE.S.@ MARSHFLATB ®
t LATE HIGHSTAND SYSTEM TRACT
I
t
[EAR~YH'OHSTANO1
[SYSTEMTRACT
j_
~-/'
m,s
®
~-?~'[l
1
I"G~"
,\
..,~,,..~.. ~-~. ":-"'"
BARS
pond
freshwater
marsh flat
ii~
==t~ PATCH-REEFS;
sawgrass prairie
~ ~
Calllanassa coquina
mounds
~=z=mrs
bar , patch-reef === ts mangrove peats & prairie
®
mollusc packstone & gra;nstone m
®
freshwater pond ts transgressive surface
,,i,uI~,1rs ravinementsurface :==::::mfs maximum flooding surface I m
JENCE BOUNDARY IAMI FORMATION
1
lm J
Fi~.A9 - S e q u e n c e s t r a t i g r a p h y Thompson Formation.
isochronous unit A
depositional
thinning-upward trend
model
of
the
Fort
The s y s t e m tracts w h i c h c o m p o s e the d e p o s i t i o n a l s e q u e n c e are the following, from b o t t o m to top: I) t r a n s g r e s s i v e system tract; 2) e a r l y h i g h s t a n d s y s t e m tract; and 3) late h i g h s t a n d s y s t e m tract (Fig.49), The d i s c o n t i n u i t y surfaces which separate parasequences are transgressive and ravinement surfaces. A maximum flooding s u r f a c e s e p a r a t e s the t r a n s g r e s s i v e from the h i g h s t a n d s y s t e m tract. Variations in the i n t e r n a l characteristics of p a r a s e q u e n c e s
83
reflect sealevel
corresponding rises.
differences
TransBressive
in
the
rates
of
relative
surface
Transgressive surfaces are r e p r e s e n t e d by a b r u p t transitions from f r e s h w a t e r swamp to m a r i n e bay l i t h o f a c i e s occurring at the bases of lowermost p a r a s e q u e n c e s (Fig.49). They reflect a r a p i d f l o o d i n g of the lagoon located b e h i n d the b a r r i e r island c o m p l e x of the A n a s t a s i a and Miami O o l i t e Formations, during sealevel highstands.Conversely, during sealevel lowstands the lagoon was a f r e s h w a t e r lake (Fig.50).
HIGHSTAND marine bay
open
sea sea level
LOWSTAND open sea
freshwater lake
sea level
Fig.50 Thompson changes.
Control of the sedimentary pattern of Formation by high-frequency relative
Ravinement
This surface pseudobreccias
is a h o r i z o n (Fig.51)
the Fort sea-level
surface
comprising
laminar
micrites
and
Laminar micrites consist of a few mm-thick, red colored laminations draping irregular subhorizontal surfaces developed m a i n l y w i t h i n the m a r i n e bay facies. T h e s e l a m i n a r m i c r i t e s are ~omp~eed ~f an a l t e r n a t i o n of darker and lighter laminae. D a r k e r l a m i n a e are c o m p o s e d of a mottled, red colored, dense mass; l i g h t e r laminae c o n s i s t of m i c r o s p a r f i l l i n g irregular, sub-horizontal,contorted voids characterized by frequent bifurcations, labyrinthic structuress and pseudofenestral
84
fabrics, fine vertical rods p r o t r u d e downward from horizontal laminae, in s o m e c a s e s cutting through shells. As s e e n from o u t c r o p s p a r a l l e l to the b e d d i n g p l a n e , the l a t e r a l c o n t i n u i t y of this thin horizon is interrupted by subcircular holes, averaging 8 c m in d i a m e t e r . In s o m e c a s e s t h e h o l e s a r e a l i g n e d along a circular perimeter. Pseudobreccias generally overlyin~ laminar micrites, are breccia-like features composed of red-colored mm-cm thick monogenic fragments surrounded by a matrix constituted by equidimensional quartz grains, a n d i n f e s t e d by the s a m e q u a r t z grains. Marine and freshwater shells occur within the m a t r i x . Clasts l o o k like p i e c e s of a j i g s a w p u z z l e ; ~oing downward, they become smaller and more numerous. P r o f i l e s s u c h as t h a t s h o w n in F i g . 5 2 , A a r e i n t e r p r e t e d as the result of r o o t p e n e t r a t i o n by m a n g r o v e root systems. Unlike c a l i c h e s or c a l c r e t e s w h i c h a l s o o c c u r in the C a r i b b e a n region (Beach and Ginsburg,1981; James, 1972), laminar micrite horizons display sharp transitions from marine carbonates to crusts,are accretionary features, do n o t t r u n c a t e bedding and lack d i a g e n e t i c textures evidencing for a s u b a e r i a l exposure. The shell truncation p r o d u c e d by t h e s e l a m i n a r h o r i z o n s is m o r e typical for roots possessing acidic properties t h a n of c a l i c h e crusts. T h e r e d c o l o r of l a m i n a e was p r o d u c e d by t h e t a n n i n e Rhyzophora manEle. T h e i n c l u s i o n s p r o d u c e d by the red m a n g r o v e present-day p e a t p r o d u c e d by the red m a n g r o v e is r e d d i s h b r o w n to dark-brown and consists of a dense mass of rootlets. Rhyzophora mangle is r e d b r o w n . Likewise, water surrounding Circular holes visible on horizontal surfaces probably represent casts of former roots.White laminae inside the laminar micrite horizon represent the i n f i l l i n g by c a l c i t e of former thin horizontal root filaments.Laminar horizons are similar to those detailed and interpreted as root mats by Wright,et ai.(1988). Pseudobreccias are interpreted as the r e s u l t of a d i s s o l u t i o n produced by the a c i d i c p e a t of the red m a n g r o v e r o o t s y s t e m . In several cases the transition b e t w e e n c l a s t s a n d the m a t r i x is gradational.The distinction between clasts and matrix is m a d e possible by a greater abundance of equidimensional quartz g r a i n s w i t h i n the m a t r i x t h a n w i t h i n the o l a s t s . I t is p o s s i b l e that quartz grains originate from the siliceous material contained in the v a s c u l a r tissues and periderm of r o o t s , once they undergo peatification (of. H o f f m e i s t e r and Multer,1965). The
development
of
red
mangrove
peat
within
marine
bay
facies
85
F I E . 5 1 - A e r i a l v i e w s of s o m e Carolina and Georgia,thought different stages of f l o o d i n g Thompson Formation.
aras alone the coasts to be representative and shallowinE up of
of s o u t h of the the Fort
86
g surtace ~ss
Freshwater pond
Tta Marsh flat ebris l~SSa
E o3 •b
s A Marine Bay
g surface
~
".............
(laminite) Freshwater
~ i ~ £ ~ j~e ~f,,--. mi~ed tauna
Marsh flat
E
u~ ": I ~ ~ , ~ J . . . - , , m a r i n e
sh¢lls
Mar)he
Bay
B
Marsh flat
Freshwater pond
and
- Parasequences formed during a quick transgression a less r a p i d sealevel r i s e d ~ s p l a y i n g laminar mi~Pites
pseudobrecc~as
(B),
CA) and
87
,
, , ,
,
C
Fi~.53 - Ravinement surface. A P r o f i l e of the l a m i n a r m i c r i t e , pseudobreccia, root casts developed above marine bay facies. B C a s t s of p r o p r o o t s a n d l a m i n a r m i c r i t e s . C~D Pseudobreccia. Root rock showing rhyzoturbated sediment.F~G D e t a i l of l a m i n a r micrites ( t h i n s e c t i o n s ) . T h e e x a m p l e v i s i b l e in G s h o w s a r o o t lamina cutting through a shell.
88
is e x p l a i n e d by the marine to b r a c k i s h coastal, intertidal m a n g l e . It f o r m s d u r i n g t h e i n i t i a l p h a s e s s e t t i n g of R h y z o p h o r a of a r e l a t i v e sealevel rise.Quick sealevel rises prevent the development of the r e d m a n g r o v e b e c a u s e t h e l i m i t of s u r v i v a l and colonization of the r e d m a n g r o v e seedling corresponds to the u p p e r s h o r e f a c e . T h e red mangrove peat transitional between f r e s h w a t e r a n d m a r i n e b a y f a c i e s is i n t e r p r e t e d as a r a v i n e m e n t s u r f a c e b e c a u s e it r e p r e s e n t s a slow reworking of a p r e v i o u s l y e x p o s e d i n t e r f a c e by an a d v a n c i n g sea. T h e p s e u d o b r e c c i a m a y be r e g a r d e d as a b i o g e n i c t r a n s g r e s s i v e conglomerate. Parasequences formed during a quick transgression are d i f f e r e n t from those developed during a slow transgression (Fig.52).The first (Fig.52A) occur at the bottom of the Fort Thompson Formation~ the s e c o n d (Fig.52B) in its u p p e r p a r t a n d in the n o r t h e r n s e c t o r , in the d e e p ramp.
Maximum
floodin~
surface
It c o n s i s t s of a c o r a l - b e a r i n g horizon (Fig.53) containing Montastrea annularis and Porites. It is interpreted as a maximum flooding surface because records the t i m e of m a x i m u m r a t e of a c c o m o d a t i o n increase: it r e c o r d s in fact a m a x i m u m deepening as s h o w n by t h e o c c u r r e n c e of fossils such as Montastrea annular~s and Porites which actually inhabit more open and deeper lagoonal areas (from -9 to -24 m below a n d the o t h e r b i o t a c o n t a i n e d sealevel) than Chione cancellata in t h e m a r i n e b a y f a c i e s .
Transgressive
facies
traqt
The transgressive facies tract, developed above the Tamiami Formation, consists of the stacking of transgressive parasequences (Fig.53,A).Their t h i c k n e s s r a n g e f r o m 3 - % m to a b o u t 1 . 2 m. The basal part is d e v e l o p e d above a transgression surface. Lithofacies are m o l l u s k g r a i n s t o n e s and packstones (marine bay Porites and Montastrea annularis. f a c i e s ) in s o m e c a s e s w i t h T h e p r o p o r t i o n a n d s i z e s o f m o l l u s k s m a y i n c r e a s e u p w a r d s u p to the h a l f of the m a r i n e lithofacies, with the production of a coarsening-upward grain size trend.
89
N 13
Hellsoma wackestone Poorly fossiliferous packstone Mollusk gralnstone and packstone
Fig,SA - Field aspect and lateral f l o o d i n g s u r f a c e ( p a r a s e q u e n c e #3).
variations
of
the
maximum
90
The lower part of the parasequence grades upwards into a strongly bioturbated packstone, as is e v i d e n c e d by sinuous galleries and shell debris-filled irregular patches. Going upwards, shell sizes d e c r e a s e . This part in turn g r a d e s to a (Helisoma wackestone).This freshwater swamp lithofacies transition is e v i d e n c e d by a m i x e d fauna containing marine m o l l u s k s and f r e s h w a t e r g a s t r o p o d s indicative for a brackish, t r a n s i t i o n a l m a r s h flat e n v i r o n m e n t , Vertical transitions from marine bay facies to freshwater lithofacies indicate an upward shallowing in a low-energy shoreline. The basal c o a r s e n i n g - u p w a r d g r a i n size t r e n d in the sequence may by interpreted as a catch-up phase of sedimentation (Kendall and Schlager,1981) during which carbonate sediment production i n c r e a s e takes p l a c e by v e r t i c a l g r o w t h as bars or p a t c h - r e e f s in o r d e r to keep pace w i t h the i n c r e a s e d rate of s e a l e v e l rise. The s u c c e s s i v e fining-upward trend may correspond to the keep-up phase (Kendall and Schlager,1981) that evidences for a lateral accretion or outbuilding of islands during a period characterized by a reduced rate of relative sealevel rise, or a sealevel stillstand. The transition to the freshwater unit may have been a consequence of an a c c e n t u a t i o n of the rate of s e a l e v e l fall during glacial periods. Barrier island faciess in the east d u r i n g these p e r i o d s b e c a m e e m e r g e n t and i n t e r r u p t e d the w a t e r e x c h a n g e w i t h the open sea, w i t h the c o n s e q u e n t t r a n s f o r m a t i o n of the bays into f r e s h w a t e r lakes s i m i l a r to those a c t u a l l y existing inh the Everglades and nearby coastal areas (cf. Fig.51). Trangressive facies tracts form a l o n g the steepest part of rising limbs of the relative eustatic curve ( Haq, et ai.,1987). This tract h e r e is e x p r e s s e d by the d e v e l o p m e n t of aggrading patch-reefs displaying coarsening-upward grain size trends which record deepenings caught-up by sedimentation, Freshwater facies capping marine lithofacies document the interference of h i g h e r order sealevel fluctuations with the lower o r d e r f r e q u e n c y s e a l e v e l rise. Correlations between cores mark a series of northward t h i c k e n i n g w e d g e s w i t h i r r e g u l a r o u t l i n e s f o r m e d by b u l g e s and d e p r e s s i o n s that r e f l e c t the c o n t r o l p l a y e d by the a n t e c e d e n t topography in the deep and s h a l l o w ramp. The Fort Thompson Formation is a northward and eastward thickening wedge (Fig. A 2 , F i g . 5 5 ) . T h e reconstructions made by Parker,at al. (1955), P e r k i n s (1977) and C a u s a r a s (1987) clearly show a
9]
A
A I
lake Okeechobee
Q5 Q4 03
lake Okeechobee Q2
Q1
S O_
M i a m i Oolite
"?.
o .O
E
--.-....__
10-
:Z I-a. I.u
Q
20-
Tamiami
30
A 33
Formation
l 29
, . I .. 23
I
]
~
r
19
13
7
3
CORES 0
8 Km
F i g . 5 5 - 0 n l a p ramp g e o m e t r i e s of the F o r t T h o m p s o n Formation (above : from P e r k i n s , 1977) showing southward and eastward thickenin~ wedges and the control played by the antecedent topography in the t r o u g h and h i n g e a r e a s . gradual thinning-out and disappearing of p a r a s e q u e n c e s towards a h i n g e l o c a t e d in the w e s t and s o u t h that i m p l i e s a r o t a t i o n a l subsidence on a w e s t e r l y s t r i k i n g h i n g e . The
rate
temporally,
of but
relative also with
sealevel change varied not only the p o s i t i o n on the p l a t f o r m , due to
92
variations in space and time of the amount and rate of rotational subsidence. T r a n s g r e s s i v e p a r a s e q u e n c e s were formed by a r o t a t i o n on the hinge: e a c h r o t a t i o n e p i s o d e led to the f o r m a t i o n of a t r a n s g r e s s i v e surface. Biological r e w o r k i n g of the s h o r e f a c e by m a n g r o v e s was p r e v e n t e d by the r a p i d i t y of the rate of s u b s i d e n c e in such a way that the shoreface was overstepped. In the north, the space a v a i l a b l e for s e d i m e n t a t i o n during a r e l a t i v e rise was f i l l e d by c a t c h - u p reefs. Sites i n t e r m e d i a t e b e t w e e n the n o r t h e r n and the s o u t h e r n area underwent a lesser amount of rotational subsidence, and s e d i m e n t a t i o n o u t p a o e d the r e l a t i v e rise and m i g r a t e d l a t e r a l l y over coeval c a t c h - u p reefs. Close to the h i n g e line, the rate of r o t a t i o n a l s u b s i d e n c e was at a m i m i m u m ; therefore, sediment c o u l d keep pace with the relative rise of the sealevel. This led to repeated a m a l g a m a t i o n s of p a r a s e q u e n c e s . The two mechanisms: aggradation in the north and lateral sediment shift in the s o u t h , l e d to d i f f e r e n t c o n t r o l s by the predepositional topography. In fact, a s t r o n g c o n t r o l can be recognized in the deep ramp, w h e r e areas of d e v e l o p m e n t of patch-reefs and bars maintain a topographic contrast with a d j a c e n t a r e a s a l o n g the e n t i r e d e p o s i t i o n a l sequence. In the south, the c o n t r o l is less e v i d e n t and d e p o c e n t e r s oscillate r a n d o m l y from one a r e a to another. These two s i t u a t i o n s are a l s o e v i d e n t from an e x a m i n a t i o n of the b l o c k - d i a g r a m s of F i g . 5 6 which show variations of the u p p e r m o s t l i t h o s o m e g e o m e t r i e s w i t h time, The r a n d o m o s c i l l a t i o n of d e p o c e n t e r areas in the s h a l l o w ramp is a n a l o g o u s to the i r r e g u l a r island shift p r e d i c t e d by the "tidal island facies m o d e l " of P r a t t and J a m e s (1986). The r e s u l t i n g p a t t e r n a l o n g an i s o c h r o n o u s stratigraphic interval is a lateral t r a n s i t i o n f r o m c o a r s e n i n g - u p w a r d to f i n i n g - u p w a r d beds that is also demonstrated by symmetrical sequences developed in i n t e r m e d i a t e positions by a migration of the fining-upward beds o v e r c o a r s e n i n g - u p w a r d beds (according to W a l t h e r ' s law).
Earlx,
highstand
facies
trac%
This tract, developed above the maximum flooding surface, consists of three early highstand parasequences (Fig.53,B)
93
o r g a n i z e d into a v e r t i c a l t h i n n i n g - u p w a r d t r e n d ( F i g . 4 9 ) . I n the basal part of these parasequences mangrove peat facies (ravinement surfaces) are interposed between underlying f r e s h w a t e r facies and m a r i n e lithofaoies. The m a r i n e bay facies contains scattered shells of Chione cancellata, fine shell d e b r i s and several root traces. This l i t h o f a c i e s g r a d e s u p w a r d s into the root rock facies and to a l i t h o f a c i e s containing a m i x e d m a r i n e and f r e s h w a t e r fauna, i n d i c a t i v e for a b r a c k i s h environment~ less commonly, the sequence is topped by s u p r a t i d a l laminites. In c o n t r a s t to the t r a n s g r e s s i v e parasequences, these record gradual flooding rates (ravinement surfaces) and gradual sealevel falls ( transitions from catch-up reefs --> m a r s h flats--> freshwater swamp). The o c c u r r e n c e of a m a r s h flat indicates that sedimentation could outpace the relative s e a l e v e l rise as a result of its s l o w i n g down. The lower parts of these p a r a s e q u e n c e s ( mangrove peat-->marsh flat-->marine bay) are analogous to the sequence recently described by Parkinson (1989) from the southwest Florida platform which consists of 2 to 6 m thick transgressive r e g r e s s i v e c o u p l e t s (paralic swamp--> r e s t r i c t e d m a r i n e - - > o p e n marine) b o u n d e d by m a n g r o v e peat facies. It is a l s o a n a l o g o u s to the cycle of F l o r i d a Bay ( Enos & P e r k i n s , 1 9 7 9 ) . As s t r e s s e d by G o l d h a m m e r , e t ai.(1990), these cycles result to be c o n t r o l l e d by 5th order sealevel fluctuations (rapid rise followed by a decelerating sealevel rise). The similar lithofacies and p a t t e r n s of c h a n g e s recorded in the early h i g h s t a n d p a r a s e q u e n c e s suggest an e v o l u t i o n s i m i l a r to that of F l o r i d a Bay and s o u t h w e s t F l o r i d a p l a t f o r m . This part of the d e p o s i t i o n a l s e q u e n c e c o n t a i n s e v i d e n c e for a eustatic control on sedimentation.Based on calculations by M i t t e r e r (1975), the u p p e r m o s t two p a r a s e q u e n c e s result to have formed in 2 5 . 0 0 0 years (Galli,1991) which approximately fit M i l a n k o v i t c h p r e c e s s i o n cycles. S u b s i d e n c e g r a d u a l l y d i m i n i s h e d d u r i n g the d e p o s i t i o n of this facies tract~ so that m a r s h flats c o u l d d e v e l o p and e u s t a t i c effects, superimposed on t e c t o n i c s u b s i d e n c e , became more evident h i g h e r up the Formation.
94
6
/
3
.,~, oo~,~
/\
3." ~ 3 0
22
3
18
19
13 7
.,"~--'-~/.~ ~
28
22 ~
6
3
Fig. 56 Block-diagrams showing variations in volume and m o r p h o l o g y of p a r a s e q u e n c e s . A lack of p r o ~ r a d a t i o n is a p p a r e n t in the hinge, in the south, whereas a southward shift of depocenters (retrogradation) c h a r a c t e r i z e s the trough.
95
Late
hi~hstand
facies
tract
T h i s f a c i e s t r a c t is c o n s t i t u t e d by a p a r a s e q u e n c e which varies in t h i c k n e s s f r o m a dm to A m. (Fig.57). The v e r t i c a l succession of l i t h o f a c i e s w i t h few c h a n g e s is the s a m e at all sites. The sequence passes from a laminar m i c r i t e h o r i z o n to a p s e u d o b r e c c i a , to the r o o t r o c k f a c i e s a n d eventually to the freshwater phytogenic breccia which is commonly the thickest lithofacies. The upper part of this parasequence may contain oolites or m u d s t o n e s typical of the overlying Miami Oolite Formation (Evans and Ginsburg,1987) which may correspond to a s h e l f m a r g i n f a c i e s t r a c t . A s i m i l a r , m o d e r n s e q u e n c e of s e d i m e n t s p a s s i n g from mud banks to f r e s h w a t e r s w a m p f a c i e s was d e s c r i b e d by C r a i g h e a d (1969), f r o m the E v e r g l a d e s National Park (Fig.16),who s h o w e d that the Everglades has p r o g r a d e d seaward more than 8 Km, d u r i n g the H o l o c e n e s e a l e v e l rise. The late highstand parasequence is interpreted as a shallowing-upward sequence f o r m e d by a d e p o s i t i o n a l regression in r e s p o n s e to a s e d i m e n t a t i o n rate in e x c e s s of t h e r e l a t i v e sealevel rise. Lateral variations in thicknesses of the parasequence d e p e n d e d on local, f o r m e r d e p t h s of the l a g o o n a l floor: in fact, thicknesses are g r e a t e r in the d e e p r a m p a n d l i m i t e d to a f e w dm in t h e s h a l l o w ramp. By a n a l o g y w i t h the m o d e r n c y c l e d e s c r i b e d by C r a i g h e a d (1969) the p a r a s e q u e n c e records a seaward shoreline progradation of a mainland produced during a declining sealevel rise, as is a l s o supported by the v e r t i c a l transitions between mangrove and freshwater lithofacies. T h e late h i g h s t a n d facies tract records the m a x i m u m rate of a c c o m o d a t i o n decrease and a continuous shallowing-up. It v e r t i c a l l y g r a d e s to the M i a m i O o l i t e w h i c h records a change from a eustatic fall to a s l o w r i s e in the sealevel. The progressive decrease in subsidence led to a progressive decrease in the control played by the predepositional topography: eventually, the d e p o s i t i o n of the parasequence formed uniquely under eustatic controls w h i c h led to a l e v e l l i n g of the t o p o g r a p h i c r e l i e f , w i t h the f o r m a t i o n of a compensation c y c l e (cf. E n o s & P e r k i n s , 1 9 7 9 ) .
96
•
.+
~ "+c
+
'~
o"-++J., ~ ' o+-~-~+.......... bird's eye ~.+~]+:.
,~.-. ++-~, •
•+/
I
' . ~ ' t ] ~ O . ~ . ~ ,%........ black
~'+'/~.'"'+
:" (~
........ wood
~> ..........
pebble
Freshwater peat
fragment
Helisoma
,.,;~.~-~o.+++......mangrove
+~>~;++.~..1 ......roo,,o+~
I
~C~-.~..'-J
Mangrove peat ......... pseudobreccia
,++~++++++~(
~--~'~t...-..
Fig,57
- Late
highstand
.......laminar mi~rite
facies
tract,
"Calcari Grigi" Formation, Jurassic, Venetian Alps
Introduction
The J u r a s s i c C a l c a r i Grigi F o r m a t i o n crops out in the V e n e t i a n Alps, Italy, at the top of the T r e n t o p l a t f o r m (Fig.58), a rimmed, isolated platform, 8000 s q u a r e Km wide, which is a p o r t i o n of an A t l a n t i c - t y p e m a r g i n s u b j e c t e d to d r o w n i n g as a result of a c o m p l e x i n t e r p l a y of e u s t a t i c p h a s e s (Bernoulli and Jenkins,197A~ Hallam,1978, 1981~ Vail and Todd,1981), s u p e r i m p o s e d on s y n s e d i m e n t a r y t e c t o n i c s (Castellarin, 1972). The e u s t a t i c c u r v e s by H a l l a m (1978) and Vail, et a i . ( 1 9 7 7 ) show a c o n t i n u o u s rise in the Jurassic. M a j o r rises took p l a c e in the H e t t a n g i a n , late Sinemurian, Pliensbachian, and at the b e g i n n i n g of the T o a r c i a n . Conversely, s e a - l e v e l falls were of less i m p o r t a n c e (Hallam,1981). It is d i f f i c u l t to a s c e r t a i n the role p l a y e d by t e c t o n i c s in the s e a - l e v e l rise. M a j o r facies c h a n g e s were p r o d u c e d by a platform collapse in the european margin (Bernoulli & J e n k i n s , 1 9 7 4 ) . The d e s t r u c t i o n of the c a r b o n a t e p l a t f o r m b e g u n in the lower Liassic (Lemoine, et ai.,1978) but continued diachronously in the southern Alps. The destruction of the T r e n t o p l a t f o r m p r o b a b l y i n i t i a t e d at a later time ( W i n t e r e r & Bosellini,1981) , at the end of the m i d d l e L i a s s i c (179 m.a.). Listric synsedimentary faults oriented NNE-SSW producing h a l f - g r a b e n s t r u c t u r e s , were m a p p e d a l o n g the w e s t e r n m a r g i n of the T r e n t o p l a t f o r m (Castellarin, 1972). A non-isostatic subsidence antecedent to the d r o w n i n g of the platform is e v i d e n c e d in the study a r e a by n u m e r o u s features (Fig.59): synsedimentary faults~slumping features,crumpled b e d s , a n d t s u n a m i t e s (Galli,1990), S y n s e d i m e n t a r y faults w h i c h were m a p p e d in the area, p r o ~ e o t e d on a S c h m i d t net (Fig.60) intersect in the SW q u a d r a n t and individuate a potential failure wedge oriented SSW. The NE q u a d r a n t c o n v e r s e l y m a y r e p r e s e n t a t e c t o n i c a l l y r e l i e v e d area. This structural frame controlled bathymetry and facies ~ distribution.
98
J
J Quaternarycover ~
~
Jurassic-Cretaceous pelagic deposits ~
CalcariGrigiFormation Triassic
O slratlgraphicsections
[]*-
F TRENTOPLATEAU-'1
~
ENTo
PLATEAU
99
W Basso
E Asiago
Sarca
Cen°m 1 Cret,
SerriasJ I1~-.
1D
Titon. !
Kimm
.,..°o.E
I~--
Saioc. :'t~-I Aalen. I] i
Giur. $Up
AMMONITICO Rosso A
/1'1 - ~
ca,,. I ~ s,,o. t 4 U ~
0 -220m
20m
•
0 -9
AMM. INF. j - " ° s s ° A~ MACHELLA -~Lo.,c.E
Toa rc. I
~ ALPINA .... ALr'=r~ '
P,//
A 2m / /
OLITE DI SAN / IGILIO / 0 - lOOm /
Glut. Upper Membl ( Membro di Ro 85m
[
med.
Giur. .,°'
i.f. Midlle Memb 35m
PI;ensb.I Lower Membe 40 m
DOLOMIA PRINCIPALE 700 - 1200 m
Trlas sup.
Slnemur.f
F i g , 5 8 - L o c a t i o n of Left: f r o m B e r n o u l l i (1981),
the study area, Above: from G~hner a n d J e n k i n s (197A) a n d B o s e l l i n i ,
Study
The in
(1981), et al,
area
s t u d y a r e a is 20 x 20 K m w i d e , It the center of the platform,
is s i t u a t e d a p p r o x i m a t e l y The thickness of the
100
Fig,59 - Features indicative for t e c t o n i c instability in t h e Trento platform, A~D~G~E~F Crumpled beds and deformation features, B Intraformational discordance. C Small-scale synsedimentary fault,G Panoramic view (locality section #4-14) showing a deformed stratigraphic horizon,
101
stratigraphic interval ranges from about 20 to 60 m,The i n v e s t i g a t i o n was c o n d u c t e d on the u p p e r part of the 'Calcari Grigi' F o r m a t i o n (upper part of the Rotzo M e m b e r a c c o r d i n g to the local stratigraphic t e r m i n o l o g y ) , w i t h i n the O r b d t o p s e l l a p r a e c u r s o r z o n e , b y means of facies a n a l y s i s of 32 s t r a t i g r a p h i c s e c t i o n s a m o u n t i n g to about 800 m. Host of s t r a t i g r a p h i c sections were c o r r e l a t e d by means of 'event c o r r e l a t i o n ' by u s i n g p h y s i c a l s u r f a c e s as time lines (for example, a triple d i s c o n f o r m i t y : Riding & Wright,1981, a dm-thick level containing radial oolites; tsunami-generated h o r i z o n s ) . T h e s e s u r f a c e s p r o v i d e d a few t r a n s e c t s w h i c h a l l o w e d for the subdivision of the stratigraphic columns into isochronous units, successively r e l a t e d to d i f f e r e n t system tracts.
Previous
studies
Various aspects of the 'Calcari i n v e s t i g a t e d by a n u m b e r of authors.
Grigi'
Formation
were
The s t r a t i g r a p h y and regional g e o l o g y r e c o n s t r u c t i o n s were made by Venzo (1963),Auboin,et ai.(1965), Castellarin (1972), Bosellini (1973a,b), B e r n o u l l i & J e n k i n s (197A), Winterer & B o s e l l i n i (1981) and B a r b u ~ a n i , et ai.(1986). Most of the work on the 'Calcari Grigi' F o r m a t i o n has been c o n c e r n e d with p a l e o n t o l o g y (Parona,192~9 Fabiani & T r e v i s a n , 1939; Wesley, 19569 V e n z o , 1 9 6 3 ) . S e v e r a l of these p a p e r s are c o n c e r n e d w i t h the d e s c r i p t i o n and i n t e r p r e t a t i o n of L i t h d o t i 8 shells, a huge m o l l u s k w h i c h is p a r t i c u l a r l y a b u n d a n t in the s t u d y area: Berti Cavicchi, et ai.(1971), Bosellini (1972), Benini & B r o g l i o L o r i g a (197~), B r o g l i o L o r i g a & Neri (1976), A c c o r s i Benini & B r o g l i o Loriga (1977), G e y e r (1977), A c c o r s i Benini (1979). The s e d i m e n t o l o g y was i n v e s t i g a t e d by V e n z o (1963), Fusanti (196&), Fuganti & M o s n a (1966), B o s e l l i n i & B r o g l i o Loriga (1971), C a s t e l l a r i n (1972), C a s t e l l a r i n and Sartori (1973a,b), Clari (1975), G ~ h n e r (1980,1981) and Galli (1990).
Facies
The the
associations
lithofacies distribution is far more c o m p l i c a t e d than in p r e v i o u s case h i s t o r y . A p u z z l i n g f e a t u r e of the 'Calcari
102
N N
Fig.60 Equiareal synsedimentary faults
pro~ection in the s t u d y
Grigi' Formation is lithofacies, grouped associations: shallow
ramp
intermediate wackestones, deep
ramp
(oncolite
of area.
the complex here into
packstone,
planes
alternation of the following
wackestones
ramp (oolite packstones and grainstones and packstones);
(thick
Lithiotis
of
and
dip-slip
several facies
grainstones);
grainstones; and
bioclast
banks).
Lithiotis shells are ubiquitous ramp; t h i c k b a n k s as m u c h as f o r m e d in t h e d e e p ramp.
9
and m
occur thick
in all s e c t o r s of the are t h o u g h t to h a v e
The different bedding s t y l e s of the t h r e e s e c t o r s of the r a m p (alternations of m e d i u m and thin beds in the shallow ramp; m e d i u m a n d t h i c k b e d s in t h e i n t e r m e d i a t e ramp and thick beds in the d e e p ramp) c a n be a p p r e c i a t e d on o u t c r o p and panoramic views (Fig.61),
Shallow
0ncolite
grainstones
and
ramp
packstones
Description This
lithofacies
consists
of
m-thick
grainstone
-
packstone
103
beds containing abundant coated grains floating in a m a t r i x constituted by a p o o r l y sorted admixture of bioclasts and l i t h o c l a s t s . S e d i m e n t a r y s t r u c t u r e s a r e t r a c e s of c r o s s b e d d i n g , rare dessication and subaerial features and channel-fills. C o a t e d g r a i n s o c c u r as s u r f i c i a l a n d l a r g e o n c o i d s ('macroids' according to P e r y t , 1 9 8 2 ) . Surficial oncoids average 3 m m in diameter, have an intraclast/bioclast, monomictic core, a clastic texture and elliptical to o v o i d a l shapes. 'Macroids' r e a c h 2 cm in d i a m e t e r ; often they have a polimictic core, a c l a s t i c to b o t r y o i d a l t e x t u r e a n d a c r u s t o s e to o v a l s h a p e . This lithofacies commonly f o r m s 0.5 m t h i c k , c o a r s e n i n g - u p w a r d cycles, developed above wackestones. These are characterized by the following vertical trends: a gradual increase in g r a i n size, grain abundance and percentage of surficial oncolites (10-25%), and sparry cement. Scours, infilled with coated grains and bioclasts (brachiopods, bivalves, gastropods and Lithiotis fragments) occur in the uppermost part. At few localities t h e t o p s of o n c o l i t e - r i c h beds are mud-cracked, or constituted by thin, r e d d i s h h o r i z o n s e n r i c h e d in l i t h o c l a s t s , or also by p a r a l l e l laminated, dm-thick, yellow, silt-size sands.
Interpretation In t h e s t u d y a r e a o n c o l i t e b e d s a r e o f t e n a s s o c i a t e d in s p a c e with Lithiotis banks and oolite beds. They represent a deposition in i n t e r b a n k , i n t e r b a r a r e a s or p o n d s l o c a t e d in the o u t e r m o s t p a r t of the s h a l l o w ramp. T r a c e s of s c o u r i n g r e f l e c t episodic mechanical reworking. Oncolite deposition is a n i n d i c a t o r of b r e a k s or s l o w i n g down in the r a t e of s e d i m e n t a t i o n , in a n e a r s h o r e or v e r y s h a l l o w environment ( W e i s s , 1 9 6 9 ) . T h e o c c u r r e n c e of l a r g e q u a n t i t i e s of large oncoids within a mudstone lithofacies was taken by C a t a l o v (1983) as an e v i d e n c e for low r a t e s of s u b s i d e n c e . Coarsening-upward cycles are interpreted as s h a l l o w i n g - u p w a r d sequences related to an upward, gradual decrease in sedimentation rate following a relative fall of the s e a l e v e l . Macroids may reflect t h e o n s e t of h y p e r s a l i n e conditions and local exposures, when associated with mudcracks, reddish horizons and keystone vugs.
104
Bioclast-lithoclast
~rainstones
and p a c k s t o n e s
Description This lithofacies is r e p r e s e n t e d by m a s s i v e to thin bedded, intraclast-bioclast grainstones and p a c k s t o n e s containing in a d d i t i o n to l i t h o c l a s t s v a r i a b l e p e r c e n t a g e s of c o a t e d grains, peloids and bioclasts (bivalves, foraminifers, Lithiotis, algae, crinoids, etc.), often enveloped by algal coatings. Oolites are rare. Lithoclasts are both r o u n d e d and angular, l i g h t - g r a y to r e d d i s h in color. Examples of bedding styles, thick-bedded and thin-bedded alternations are s h o w n in F i g . 1 4 , 1 5 and 17. The most typical s e d i m e n t a r y s t r u c t u r e is g i v e n by scours r a n g i n g in a m p l i t u d e from a few dm to I0 m. Some beds may r e s u l t from m e r g i n g and s t a c k i n g of c h a n n e l structures w h i c h do not e v i d e n c e for any facies v e r t i c a l t r e n d (Fig.17). A common sequence encountered in this lithofacies ranges between 0.5 and 1.5 m in t h i c k n e s s and consists of three units.The basal part has an e r o s i o n a l base, a disorganized m a s s i v e bed c o n t a i n i n g fossils w h i c h in some cases are d i s p o s e d in p a r t i n g lineations,traces of h u m m o c k y cross-bedding and undulations of uncertain origin. This basal part appears structureless when the composition and grain size are h o m o g e n e o u s . T h e basal part passes up g r a d a t i o n a l l y to a b e t t e r sorted unit characterized by intrastratal, scalloped u n d u l a t i o n s and v a r i o u s types of w a v e - g e n e r a t e d s t r u c t u r e s such as c l i m b i n g - w a v e r i p p l e l a m i n a t i o n ( K r e i s a , 1 9 8 1 ) , or very thin, slightly undulated, flattened plane lamiantion. Traces of ripples are also p r e s e n t with amplitudes of about 8 cm and heights of 4 cm. The upper unit consists of well sorted i n t r a s p a t i t e s o r g a i n z e d into laminae, i n t e r b e d d e d in some case w i t h lime m u d s t o n e s . This c y c l e records an o v e r a l l g r a i n size fining-upward
trend.
Interpretation This
lithofacies
reflects
a
deposition
in
a
shallow
lagoonal
environment. The c y c l e is a n a l o g o u s to i n t e r p r e t e d n e a r s h o r e storm d e p o s i t s d e s c r i b e d by K r e i s a ( 1 9 8 1 ) , B r e n c h l e y & N e w a l l (1982), K u m a r & S a n d e r s (1976), M o u n t (1982), and others. T h e y are i n t e r p r e t e d as t h i c k - b e d d e d alternations (see above). The tops of these cycles c h a r a c t e r i z e d by thin s t o r m - g e n e r a t e d beds a l t e r n a t i n g with fairweather muds are interpreted as thin-bedded alternations
105
Lime
mudstones
Description T h i s l i t h o f a c i e s o c c u r s as t h i n i n t e r b e d s w i t h o t h e r f a c i e s . It overlies subaerial surfaces or m a r i n e unconformities. It is also frequently sandwiched between marine lithofacies. It c o n s i s t s of b l a c k , calcareous, clayely deposits containing at p l a c e s a b u n d a n t p l a n t d e b r i s a n d m o r e r a r e l y t r a c e s of s u l p h a t e minerals. Thicknesses average 1 0 - 2 0 cm. T h e y f o r m t h i n - b e d d e d alternations with homogeneous, dm-thick mudstones containing rare ostracods. These interbeds are completely lacking of macroskeletal constituents. Similar lithofacies i n v e s t i g a t e d by Castellarin and Sartori (1973) in a n e a r b y location revealed that the mud contains traces of i l l i t e and hematite, and/or goethite ,quartz and chlorite. Interpretation This lithofacies was interpreted as a mud flat or marsh environment (Bosellini & Broglio Loriga,1971). Marl deposits form in a n u m b e r of d i s t i n c t subenvironments, which may be c o l o n i z e d by a d e n s e v e g e t a t i o n . They were described from shallow ponds ,coastal marshes, and freshwater lakes. In the ponds and lakes, such as the E v e r g l a d e s , m a r l s o c c u r at the b a s e of a t r a n s g r e s s i v e sequence as the s e a l e v e l r i s e s a n d as a r e s u l t of a p r o g r e s s i v e r i s e of the f r e s h w a t e r lens ( M o n t y a n d H a r d i e , 1 9 7 6 ) . It m a y a l s o f o r m at the top of a r e g r e s s i v e sequence w h e n the m a r s h p r o g r a d e s over a retreating shoreline, as o c c u r s on the e a s t e r n h a l f of Andros Island,Bahamas. Marls also form over exposed surfaces during prolonged periods of lowstand. Coastal marshes can represent the transitional zone between freshwater marls and marine calcareous mud. In t h e s e cases, intrusions by m a r i n e sediments during storms produce interbedded freshwater and marine sequences (thin b e d d e d a l t e r n a t i o n s ) .
Intermediate
Oolite
srainstones
and
ramp
packstones
Description On o u t c r o p
this
lithofacies
is
a
massive
bedded,
light-gray
to
106
creamy, homogeneous packstone and grainstone containing concentrical, tangential colds (amounting to a b o u t 30-40%). Wackestones a r e m u c h less c o m m o n . This lithofacies is m o s t w i d e s p r e a d in the T r e n t o p l a t f o r m a n d in its t o p m o s t p a r t .
eastern
area
of
the
Two lithofacies can be distinguished (Fig.22). The first, p o o r l y s o r t e d , is c o m p o s e d of s u r f i o i a l o o l i t e s a n d l u m p s a n d a m i x t u r e of i n t r a c l a s t s , peloids and coated grains, other than s e v e r a l t y p e s of s k e l e t a l g r a i n s s u c h as f o r a m i n i f e r s , o s t r a c o d s and algae which constitute the n u c l e i of ooids. The second lithofaoies,less common,consists of well sorted oolite grainstones. Sedimentary structures are large-scale hummocky cross-bedding, rare tabular cross bedding, symmetrical megaripples and horizontal lamination. Smaller scale structures include flute casts, scours infilled with mud and coated grains, and dubious load casts. Half-cm thick, lenticular coquinites composed of densely packed, imbricated, both articulated and disarticulated s h e l l s of b i v a l v e s a r e f o u n d f r e q u e n t l y intercalated with some of the t h i c k e r b e d s . G r a d e d b e d s a r e c o m m o n . S o m e o u t c r o p s s h o w upward transitions f r o m t h e p o o r l y s o r t e d , to the w e l l s o r t e d oolite
lithofacies.
In the s t u d y a r e a t h i s it m o s t l y o c c u r s o n top
lithofacies of s h o a l s .
has
a
patchy
distribution:
Interpretation These massive bedded, oolite grainstones and packstones are interpreted as shoals, banks and sandwaves situated in a storm-dominated area, at a shallow-water depth. Storms were mainly responsible for the cold migration. Oolitic sand shoals are found actually along the edges of several Bahama areas (i.e. Cat Cay, Joulters Cay, Berry Islands, etc.). They occur as I) n a r r o w , active cold shoals marginal to the o p e n sea; a n d 2) as s t a b i l i z e d cold-aggregate grains-pelletal sands flats forming widespread blanket sheets behind active sand shoals and grading to other platform sediments (Multer, 1977). Skeletal admixtures are greatest in the d e e p e r s i t e s . These two modern well sorted and
sediment types correspond respectively to the poorly sorted oolite lithofaoies. Transitions
107
from the p o o r l y sorted to the well s o r t e d l i t h o f a c i e s indicate a shallowing of the s e d i m e n t a r y interface consequent to a d e p o s i t i o n a l r e g r e s s i o n (of, Van S t e e n w i n k e l , 1 9 9 0 ) .
Skeletal
wackestones
Description These places
thin-medium bedded, light-gray wackestones contain at a b u n d a n t , thin shells of b i v a l v e s (Pholadomia, Gresslya, pectinidae) and m i n o r q u a n t i t i e s of g a s t r o p o d s . Other skeletal constituents are thin-shelled brachiopods, crinoids (Isochrinus), foraminifers (Paleodasycladus, Orbitopsella occasional Lithiotis and other undetermined praecursor), microfossils. Small, reddish intraclasts are found n e a r the base of some of the less f o s s i l i f e r o u s beds, Coated grains o c c u r i n f r e q u e n t l y t h r o u g h o u t this lithofacies,
A v a r i e t y of this l i t h o f a c i e s is c o n s t i t u t e d by thin beds (I0 20 cm thick) of p o o r l y fossiliferous, dark-colored mudstones w i t h i n t e r s p e r s e d s a n d - s i z e grains. This l i t h o l o g y is t y p i f i e d by n o d u l a r i t y which gives way to p s e u d o b u d i n s , and lensoid n o d u l e s w i t h l a m i n a t e d clay s e a m s . B i o t u r b a t i o n is d o m i n a t e d by Thalassinoides burrows w h i c h may have c o n t r i b u t e d t o g e t h e r w i t h p r e s s u r e s o l u t i o n to the f o r m a t i o n of the n o d u l a r i t y . Sedimentary structures c o n s i s t of irregular, erosional scours (a few cm to some dm wide), symmetrical megaripples, gutter casts and hummocky cross-bedding. Fenestrae are rare. Coquinites are composed of I) gastropod streaks forming pebble-cluster a l i g n m e n t s p a r a l l e l or d r a p i n g the s y m m e t r i c a l u n d u l a t i o n s , and, more commonly, of 2) lenses of b i v a l v e s that are e s s e n t i a l l y t h i n - s h e l l e d , of the same size, c o n v e x - s i d e up and d r a p i n g the topsets of s y m m e t r i c a l megaripples. Few of these lenses are o r g a n i z e d into 20 cm thick fining-upward cycles composed of: I) a lower grainstone-packstone unit consisting of r a n d o m l y oriented bivalves; 2) a t h i n n e r unit with c o n v e x - u p shells; and 3) an u p p e r mud r i p p l e d top or an argillaceous, yellow cm-thick horizon. Multistored, complex lenses containing coquinites are volumetrically less r e p r e s e n t e d than w a c k e s t o n e layers.
Interpretation This lithofacies oolite grainstone
was deposited at a d e e p e r depth than the and p a c k s t o n e lithofacies, as is s u g g e s t e d by
108
Fi~,61 Beddins styles of deep ramp (A:thick banks), intermediate r a m p ( B ; t h i c k a n d t h i n b e d s ) a n d s h a l l o w r a m p (C: thin beds),The panoramic v i e w of M , T e s t o (D9 l o c a l i t y s e c t i o n s #15 and 28) shows a transition from shallow to deep ramp e v i d e n c e d by an u p w a r d i n c r e a s e in b e d t h i c k n e s s and declivity (a h i ~ h e r e r o s i o n in the s h a l l o w r a m p is f a v o u r e d by f r e q u e n t intercalations of lime m u d s t o n e s ) ,
109
the t r a n s i t i o n and lateral c h a n g e s to Lithiotis w a c k e s t o n e s . Similar bathymetric relationships b e t w e e n skeletal and o o l i t e beds occur in m o d e r n areas, for e x a m p l e at Lily B a n k (see also Hine,1977: Fig.2~) w h e r e s k e l e t a l w a c k e s t o n e s o c c u r in deeper, s e a w a r d sites (-5 to -I0 m b e l o w s e a l e v e l ) . This facies formed as lime mud thickets. Intense b i o t u r b a t i o n in more p r o t e c t e d , less p o p u l a t e d by Thalassinoides o c c u r r e d Thalassinoides burrows indicate however areas. Truncated e p i s o d i c erosion, as is s u p p o r t e d by the o c c u r r e n c e of o t h e r storm-generated structures, such as hummocky cross-bedding, wave m e g a r i p p l e s , c o q u i n i t e s , etc.
Deep
ramp
Lithiotis w a c k e s t o n e s Description
Lithiotis w a c k e s t o n e s are w i d e s p r e a d in the T r e n t o p l a t f o r m . They are t y p i f i e d by thick beds (I to 9 m) of t i g h t l y p a c k e d problematica, accumulations of huge pelecypods ( Lithiotis Cochlearites loppianus, Lithopedalium, Gervilleioperna, etc.) as much as A0 cm long and e m b e d d e d in a w a c k e s t o n e matrix. Other fossil types such as crinoids, corals, brachiopods, algae, (Orbitopsella praecursor, Glomospira,Textularia) foraminifers and sponge spicules are only accessory components, as this biofacies represents a suspension feeder, olygotypic a s s o c i a t i o n (Broglio L o r i g a & N e r i , 1 9 7 6 ) . Lithiotis display various fabrics: vertical, Shells of fanning-upward clustering, imbricated, wave knitted (bidirectional shell orientations). The u p w a r d decreases in shell sizes result in a f i n i n g - u p w a r d trend. Sedimentary structures are various types of scours and undulated bedforms (Galli,1990). In this s e c t o r of the ramp Lithiotis alternate with skeletal thick beds composed of wackestones (trough sequences: F i g . 2 3 D ; F i g . 6 1 A ) .
Interpretation Thick
banks
represent
a deposition
in d e e p e r
areas
of the
ramp
II0
111
AXES OF SCOURS
Km 0
I
2
3
4
~=
f
112
f~
J
SYMMETRICAL RIPPLES"
LITHIOTIS SHELLS ~-2~"~
\
113
Fig.62 - Contour maps and paleocurrent data of the study area. The isocoquinite map results from contouring sites characterized by the same n u m b e r s of c o q u i n i t e lenses; the v a l u e s w e r e o b t a i n e d by d i v i d i n g the n u m b e r of o o q u i n i t e lenses within skeletal wackestones by the thickness of skeletal wackestones occurring in s t r a t i g r a p h i c sections.The frequency of c o q u i n i t e lenses d e c r e a s e s t o w a r d s n o r t h e a s t , w h i c h is the s h a l l o w e s t s e c t o r of the ramp (of. the p r o x i m a l i t y distality concepts shown schematically in Fig.15).The isopac map of Lithiotis banks also reflects changing water depth because t h i c k beds of t i g h t l y p a c k e d a c c u m u l a t i o n s of big shells of Lithiotis problematica GOmbel took p l a c e in the deep r a m p . A n examination of the c o n t o u ~ maps r e v e a l s the e x i s t e n c e of an elongated lagoonal depression oriented NE-SW. The lagoonal floor was uneven due to the development of an array of shoals.Directional data i n d i c a t e a d o m i n a n t rotary h i g h - e n e r g y path oriented SW-NE driven by the lagoonal corridor c o n f i g u r a t i o n and a minor mode, o r i e n t e d S E - N W w h i c h indicates c u r r e n t s f l o w i n g o b l i q u e to the lagoonal c o r r i d o r . M e a s u r e m e n t s from shell imbrications and p a r t i n g lineations suggest that c u r r e n t s m o v e d from SW to N E . A r e f r a c t e d wave p a t t e r n w h i c h d i s p l a y s a c o u n t e r c l o c k w i s e sense of r o t a t i o n p r o b a b l y r e s u l t e d from the i m p i n g e m e n t of the S W - N E o r i e n t e d c u r r e n t upon shoals l o c a t e d in the east. P r o b a b l y most of c u r r e n t s and waves were p r o d u c e d by t s u n a m i s ( of. G a l l i , 1 9 9 0 ) . A s suggested elsewhere ( G a l l i , 1 9 9 0 ) , t h e s t o r m s y s t e m , r a t h e r than a c t i v e l y t r a n s p o r t i n g sediment, determined near-bottom oscillating currents acting through strongly pulsating bursts of e n e r g y . S t r o n g pressure p u l s e s on and b e l o w the lagoonal floor and s t r o n g shear stress produced an 'in situ' reorientation od shells. Large-scale b e d f o r m s , n o t d e s c r i b e d in this work, were p r o b a b l y g e n e r a t e d by tsunamis, as s u g e g s t e d by their formation by the a c t i o n of s u r f a c e waves, a great lateral extent of e x p o s u r e s and t h e i r r e s t r i c t i o n to the same s t r a t i g r a p h i c h o r i z o n s (for d i s c u s s i o n see Galli,1990). Earthquakes within the platform may have produced sudden oscillations of w a t e r w h i c h incorporated the w h o l e w a t e r column.
Fig,63 - North-south cross s e c t i o n showing the w e d g e - s h a p e d g e o m e t r y of the s t u d i e d p a r t of the 'Calcari Grigi' F o r m a t i o n . A lack of p a r a l l e l i s m between time lines (base of the early h i g h s t a n d s y s t e m tract and radial o o l i t e h o r i z o n i n t e r p r e t e d as a type-2 unconformity) is taken as an evidence for s y n s e d i m e n t a r y tectonics.
114
tUO
01.
t
8~;
~
9
61. cj
6
t
L
91,
g
I.I,
115
as is s u g g e s t e d by the g r e a t t h i c k n e s s e s ( as m u c h as 7 - 9 m), l a c k of e r o s i o n a l s t r u c t u r e s , lack of s u p p l y of i n t r a c l a s t s a n d a n d / or s k e l e t a l d e b r i s . W a t e r c i r c u l a t i o n was l i m i t e d as t h e faunal diversity is low. T h i n L i t h i o t i s b e d s , I to 2 m t h i c k ,were p r o b a b l y d e p o s i t e d in s h a l l o w e r a r e a s , c l o s e to the i n t e r m e d i a t e ramp. T h e s e t h i n n e r Opisoma, and beds contain in f a c t t h i n - s h e l l e d brachiopods, o t h e r s k e l e t a l f r a g m e n t s t y p i c a l of the i n t e r m e d i a t e ramp. Hummocky structures and other mechanical sedimentary structures evidence for strong episodic disturbances by w a v e s r e s p o n s i b l e for r e w o r k i n g of L i t h i o t i s s h e l l s . The occurrence fluctuations fluctuations.
of t r o u g h possibly
sequences related
suggests some bathymetric to relative sealevel
Paleobathymetry
A n e s t i m a t e of b a t h y m e t r y of the s t u d y a r e a was c a r r i e d o u t by constructing the isopach map of the maximum thicknesses of Lithiotis banks. The existence of a l a g o o n a l bucket oriented NE-SW is r e v e a l e d by t h e i s o p a c h map, Deeper lagoonal areas (deep ramp) are located in the w e s t and south. Directional data, s u m m a r i z e d in F i g . 6 2 a n d 26, c o l l e c t e d from orientations of symmetrical wave ripple crests, gutter casts, axes of coquinite lenses, channels and from the longest axes of L J t h i o t i s s h e l l s , i n d i c a t e that, w h a t e v e r the o r i g i n (storms, tsunamis,etc.) currents paths were controlled by the paleotopography and bucket configuration. In c r o s s s e c t i o n , the s t u d i e d u p p e r p a r t of the ' C a l c a r i G r i g i ' Formation is wedge-shaped (Fig,639 cf. also Fig.58). The northeastern side, 20 m t h i c k , is m a i n l y c o m p o s e d of s h a l l o w ramp lithofacies. It formed at a s h a l l o w e r depth than the southern side where the sedimentary p r i s m , 60 m t h i c k , w a s t h e s i t e of a c c u m u l a t i o n of the t h i c k e s t L i t h i o t i s b a n k s , The sedimentary wedge corresponds to an i n t r a s h e l f onlap ramp w h o s e h i n g e is l o c a t e d in the n o r t h a n d n o r t h e a s t ~ the flexure area is oriented north-south. The lagoonal trough strikes northeast southwest. A graphic simulation obtained by interactive modelling shows a hypothetical representation of the p a l e o b a t h y m e t r y of the ramp surface which was inclined
116
4\
SHALLOW
'~
1-"---"'-/ BIOCLAST ~ . BANK
~
Fig.6A
~ WASHOVER
RAMP
MARSH WA,SHOVER BIOCLASTBANK
DISCONTINUITIES
MARSH
- Transgressive
DEEP RAMP
system
tract,
117
towards west and southwest and c o r r e s p o n d i n g to s a n d w a v e s and banks
Depositional
punctuated (Fig.26).
by
sequence
The stratigraphic interval represents a third depositional s e q u e n c e w h i c h is s u b d i v i d e d from b o t t o m into a transgressive facies tract, an early and h i g h s t a n d facies tract and a shelf m a r g i n facies tract.
Transgressive
relieves
facies
order to top a late
tract
Description This facies tract is c o n s t i t u t e d by the f o l l o w i n g of l i t h o f a c i e s , s u m m a r i z e d b e l o w from b o t t o m to top I) Scoured undulating,
alternation (Fig.6~).
packstone with reddish lithoclasts passing n o d u l a r b l a c k lime m u d s t o n e s (shallow ramp);
to
2) G r a d e d bioclast layers, each characterized by an u p w a r d increase in the p r o p o r t i o n of l i t h o c l a s t s and c o a t e d g r a i n s ( w a s h o v e r d e p o s i t - t h i c k - b e d d e d a l t e r n a t i o n : s h a l l o w ramp); 3)
Lime
mudstones
(shallow
ramp);
~) S t a c k e d c o a r s e n i n g - and t h i c k e n i n g u p w a r d layers r e c o r d i n g a progressive increase in the b i o c l a s t percentage. G r a i n sizes d i s p l a y some b i m o d a l i t y ; p e l o i d a l g r a i n s are well sorted and m i c r i t i z e d ( i n t e r m e d i a t e ramp).
Interpretation The sequence analogous to W r i g h t (1981) Zechstein.
is interpreted as a hinge sequence. It is the littoral barrier described by Riding and and to the H a m p o l e beds o c c u r r i n g in the E n g l i s h
Transitions r e c o r d e d by the s e q u e n c e and m u d flats to an i n t e r m e d i a t e ramp p o i n t to a d e e p e n i n g - u p w a r d trend.
from s h a l l o w ramp p o n d s s u b m a r i n e b i o c l a s t i c bar
118
~'f---*-'-~SEA LEVEL CURVE
IOTIS BANK
HINGE
mO,
~
.~ .=
~.~,"
7m
Fi~.65 system
- Early tract.
highstand
119
Changes in the relative sealevel were discontinuous as individual assemblages of lithofacies are separated by d i s c o n t i n u i t y surfaces. The l o w e r m o s t surface is scoured. It f o r m e d above a h o r i z o n of likely s u b a e r i a l o r i g i n and is i n t e r p r e t e d as a t r a n s g r e s s i v e surface. It c o r r e s p o n d s to the lower s e q u e n c e b o u n d a r y of the depositional sequence.The former pedogenetic horizon above w h i c h the s e q u e n c e was d e p o s i t e d is r a r e l y p r e s e r v e d . It is m o s t l y inferred from a b u n d a n t r e d - c o l o r e d l i t h o c l a s t s o c c u r r i n g at the very bottom. The scarce micritization of grains c o n t a i n e d w i t h i n the lowermost g r a d e d beds (washover d e p o s i t s in the s h a l l o w ramp) and the p r e s e r v a t i o n of w a s h o v e r d e p o s i t s point to an increase in the rate of the relative sealevel r i s e . A s u c c e s s i v e s l o w i n g in the speed of the r e l a t i v e sealevel rise si indicated by the occurrence of intraclasts and m i c r i t i z e d grains on top of the s h a l l o w ramp lithofacies. The t r a n s i t i o n to the b i o c l a s t bank m a r k s an i n c r e a s e in the deepening-upward trend. The s u r f a c e which separates the two sectors of the ramp c o r r e s p o n d s to a r e t r o g r a d a t i o n a l line (see c h a p t e r #3 for the d e f i n i t i o n of r e t r o g r a d a t i o n a l line). The s e q u e n c e r e p r e s e n t s a r e t r o g r a d a t i o n a l t r a n s g r e s s i v e facies tract. Sediment was transported hingeward and formed a s t r i n g - l i k e body which may c o r r e s p o n d to a t h i n - s h e e t l i t h o s o m e as d e f i n e d by Burchettej et a ! . ( 1 9 9 0 ) . The low s e d i m e n t a t i o n rate was b a r e l y s u f f i c i e n t to c o u p l e w i t h the r i s i n g sealevel.
Early
highstand
facies
tract
Description The early h i g h s t a n d facies tract is a w a c k e s t o n e bank c o m p o s e d (Fig.65). The t h i c k n e s s d e c r e a s e s of thick shells of L i t h i o t i s from the t r o u g h area in the s o u t h w e s t (7 m: s e c t i o n # 25) to the h i n g e area in the NE (2.7 m: s e c t i o n #8). Faunal d i v e r s i t y is h i g h e r in the t r o u g h area. The thickest beds in the southwest (trough area) record vertical changes in fabric and c o m p o s i t i o n of L i t h i o t i s and sedimentary structures. Fabrics vary from p a r a l l e l (in some i n s t a n c e s found in p h y s i o l o g i c a l position) to w a v e - k n i t t e d , to r a n d o m t o w a r d s the top. L i t h i o t i s c o m p r i s e L i t h i o t i s sp. ss. and Cochlearites in the lower and m i d d l e part of the bank, and GervJlleJoperna in its upper part. Shell sizes a l s o d e c r e a s e
120
from 5cm - 2 0 + 3 0 cm at the bottom, to I-3 cm t o w a r d s the top. T r a c e s of s c o u r s f i l l e d w i t h r a n d o m l y o r i e n t e d Lithiotis shells and t r a c e s of cross b e d d i n g o c c u r at the top of the bank. This Lithiotis bank grades upwards to grainstones containing Lithiotis and o t h e r b i o c l a s t s such as small-size dispersed foraminifers, algae and g a s t r o p o d s . The top is also e n r i c h e d in o n c o l i t e s and i n t r a c l a s t s . A l l o c h e m s are m i c r i t i z e d . The u p p e r grainstone unit records also coarsening-upward as well f i n i n g - u p w a r d g r a i n size trends.
Interpretatio n This that that
bank formed in the deep r a m p . T h e lithosome geometry is of a wedge. D e c r e a s e s in t h i c k n e s s from NE to SW indicate the s e d i m e n t a r y interface was s l i g h t l y inclined towards
south. The lower p a r t of the bank c o n t a i n i n g t h i c k shells of Lithiotis f o r m e d w h e n the a c c o m o d a t i o n potential was highest: the h i g h s e d i m e n t a t i o n rate f a v o u r e d the d e v e l o p m e n t of Lithiotis; this part of the b a n k c o r r e s p o n d s to a m a x i m u m f l o o d i n g surface. The b a n k is c o m p a r a b l e to o t h e r c a t c h - u p reefs d e s c r i b e d in the literature (Fig.28) which record a transition from a quiet~ deep water stage to a shallower water stage typified by d e t r i t u s and l i t h o c l a s t s a s s o c i a t e d w i t h fossils. This early highstand facies tract records an aggradational trend d u r i n g w h i c h the space c r e a t e d by the r i s i n g s e a l e v e l was i n f i l l e d by vertical sediment growth ('catch-up phase' by K e n d a l l and S c h l a g e r , 1 9 8 1 ) . The p r o g r e s s i v e relative sealevel fall of the s e d i m e n t a r y i n t e r f a c e p r o d u c e d by the p i l i n g - u p of shells led to the d e p o s i t i o n at a s h a l l o w e r w a t e r d e p t h w h i c h thickets.Then, the favoured the f o r m a t i o n of Gervilleioperna d e c r e a s i n g s p a c e a v a i l a b l e to s e d i m e n t a t i o n f a v o u r e d a lateral facies s h i f t and p r o g r a d a t i o n w h i c h is d o c u m e n t e d by the set of compositional and fabric f e a t u r e s o c c u r r i n g at the top of the bank. T h e s e c h a n g e s r e f l e c t the i n i t i a t i o n of the late h i g h s t a n d facies tract phase of s e d i m e n t a t i o n . T h e vertical transition from L i t h i o t i s to Gervilleioperna a p p e a r s to be a primary f u n c t i o n of the d e c r e a s i n g s e d i m e n t a t i o n rate, in k e e p i n g w i t h the r e s u l t s obtained by Rey et a i . ( 1 9 9 0 ) from south Spain, r a t h e r t h a n a m a i n f u n c t i o n of d i f f e r e n t d e p t h s of d e p o s i t i o n of the two bivalves,as suggested by B r o g l i o Loriga & Neri (197~); interpretations which assign different depths to f o s s i l i z e d o r g a n i s m s w i t h i n a c a r b o n a t e p l a t f o r m are f r e q u e n t l y based on some sort of c i r c u l a r r e a s o n i n g ; conversely, their i n f e r r e d d e p e n d a n c e of the r e l a t i v e rise in the sea level may be c o n f r o n t e d
with
independent
data,
121
Late
hi~hstand
facies
tract
Description T h i s p h a s e is a p p r o x i m a t e l y 7 m t h i c k a n d c o n s i s t s of a n u m b e r of grain-supported, thinly bedded oncolite bioclast intraclast- bearing lithofacies interbedded with lime mudstones SHALLOW
RAMP
s.l.
7m OOLITES
BLACK MtCRITES COATED GRAINS
- Late
highstand
facies
tract.
Individual thin beds are organized into finingand coarsening-upward grain size trends. In the northern area, close to the hinge (sections # 8,11 and 18: Fig.63), coarsening-upward cycles are predominating. Fining-upward c y c l e s a r e m o s t c o m m o n t o w a r d s the t o p of t h i s t r a c t a n d in t h e south. In t h e m o s t p a r t of the stratigraphic sections this tract records a recurring change in the composition of grain-supported beds intercalated with lime mudstones from b i o c l a s t --> o o l i t e - - - > to o n c o l i t e . T h i s t r a c t is t o p p e d by a c m - t h i n h o r i z o n of r a d i a l o o l i t e s .
Interpretation Deposition took place in a shallow ramp.The frequency of oncolites within micrites and pisolite-oncolite grainstone beds p o i n t to a r e d u c e d s e d i m e n t a t i o n rate. S o u t h w a r d c h a n g e s in t h e thickness, l i t h o f a c i e s a n d t y p e s of b e d s s h o w t h a t the s o u t h e r n z o n e w a s d e e p e r . T h e o c c u r r e n c e of 6 - 7 m t h i c k o o l i t e b a n k s in the s o u t h ( s e c t i o n # 25: Fig. 63) a n d o o l i t e storm deposits
122
( s p i l l o v e r and w a s h o v e r d e p o s i t s ) in the n o r t h a l o n g the same stratigraphic horizon suggests northward,hingeward directed storm pro~esses. Grain-supported beds are interpreted as t h i c k - b e d d e d a l t e r n a t i o n s w h i c h formed s h a l l o w i n g - u p w a r d c y c l e s as is d o c u m e n t e d by e m e r s i o n f e a t u r e s on tops r e s u l t i n g from h i g h - f r e q u e n c y s e a l e v e l changes. The overall l i t h o l o g i c t r a n s i t i o n s of g r a i n s t o n e - p a c k s t o n e beds i n t e r c a l a t e d with lime m u d s t o n e s indicate a p r o g r e s s i v e u p w a r d s h a l l o w i n g trend. M i g r a t i o n s a r o u n d s c a t t e r e d d e p o c e n t e r s took p l a c e d u r i n g this time i n t e r v a l . T h e p h y s i o g r a p h y was p r o b a b l y a n a l o g o u s to that c h a r a c t e r i z i n g a n u m b e r of p e r i t i d a l s e t t i n g s located within carbonate platforms typified by p r o s p i c i e n t s u b m e r g e d and e m e r g e n t areas, The uppermost thin radial oolite horizon documents the e s t a b l i s h m e n t of u n i f o r m e n v i r o n m e n t a l c o n d i t i o n s in the area,
Shelf mar~in
facies.tract
Description This tract o v e r l i e s the h i g h s t a n d facies tract and is o v e r l a i n by p e l a g i c lithofacies. It is c h a r a c t e r i z e d by the p r e d o m i n a n c e of l i t h o f a c i e s typical of the i n t e r m e d i a t e ramp. The u p p e r m o s t part of the 'Calcari Grigi' F o r m a t i o n c o n s i s t s in fact of several repetitions of the following type of alternation of l i t h o f a c i e s (Fig.67) : o o l i t e g r a i n s t o n e s --> L i t h ~ o t ~ s bank--> s k e l e t a l w a c k e s t o n e s (intraclast - bioclast p a o k s t o n e s and g r a i n s t o n e s ) , This sequence averages 7 m in thickness. Its time interval of formation, c a l c u l a t e d by u s i n g the m e t h o d d e s c r i b e d by G r o t z i n g e r (1986),is of about 1 9 0 , 0 0 0 years, This tract is c h a r a c t e r i z e d by a lack of thin b e d s . F a c i e s t r a n s i t i o n s are sharp. Thin, lime m u d s t o n e h o r i z o n s o c c u r at the b o t t o m and top of the o o l i t e l i t h o f a o i e s , B i o c l a s t s are scarcely
micritized,
Interpretation T h e s e 7 m thick a l t e r n a t i o n s are the p r o d u c t of a h i n g e w a r d , s t e p w i s e m i g r a t i o n of i n t e r m e d i a t e l i t h o f a o i e s , a s is s h o w n by
123
the d i s t r i b u t i o n of o o l i t e bodies (Fi~,63). The r e l a t i v e s e a l e v e l rise i n i t i a l l y led to the f o r m a t i o n of oolite sediments; successively,the space created by the sealevel rise was c o l o n i z e d by L i t h i o t i s w h i c h formed banks t h i n n e r than those o c c u r r i n g in the deep ramp. T h e s e banks are in turn o v e r l a i n by s k e l e t a l w a c k e s t o n e s and/or bioclast and i n t r a c l a s t E r a i n s t o n e s w h i c h point to a s h a l l o w i n g - u p , These s e q u e n c e s are i n t e r p r e t e d as d e e p e n i n g - u p w a r d sequences c a p p e d by s h a l l o w e r w a t e r facies w h i c h were d e p o s i t e d f o l l o w i n ~ a s l o w i n g d o w n of the rate of sealevel rise,The deepeningu p w a r d t r e n d is also d o c u m e n t e d by the s c a r c i t y of m i c r i t i z e d grains and i n t r a c l a s t lithofacies,
m 7
lntraclast, oncolite, bloclast oohte
'@.~ ' £ ~ ! t
/
,,mestones
:- ~ ' ~ - @ ~
.-
""L
/INTERMEDIATE
,,,,,o,i. wac e.tone
/
I\
RAMP I
\
.
/
" DEEP RAMP
~ " ~ " ~
~,~o6.%%J g.~__%~$'2~4
~
Discontinuity .uotl~e . . . grams~one . .
"~"~ BmliacCrkte
/ / /
"" INTERMEDIATE RAMP .......
Rate of sea-level change
'J
•
Markovian
• Shallower
/ /
Deeper
sequences
e~ oe°
Fi~,67
- Modal
cycle
of
the
shelf
margin
facies
tract.
In the s t u d y a r e a the S M S T is o v e r l a i n by d i f f e r e n t pelagic facies of various ages (Rosso Ammonitico; Oolite di San Vigilio9 T e n n o F o r m a t i o n ) . It follows that the d i a c h r o n o u s top of the C a l c a r i Grigi c a n n o t be c o n s i d e r e d as a f l o o d i n g s u r f a c e as s t a t e d by B a r b u ~ a n i , et ai,(1986),
124
Model
of d e p o s i t i o n
The TST c o r r e s p o n d s to a b a r r i e r - l a g o o n littoral facies; the e a r l y HST to a c a t c h - u p reef; the late HST to a p r o g r a d i n g mud flat; the S M S T r e p r e s e n t s the l a n d w a r d m i g r a t i o n of an o o l i t e b a r r i e r facies. The s t a c k i n g of these d i f f e r e n t depositional faciess is typical of mature, l o n g - l i v e d p l a t f o r m s . Sedimentation took place mainly retrogradational mechanisms. A limited d u r i n g p e r i o d s of s l o w i n g - d o w n of the (late H S T and top of the SMST). A general
transgressive
trend
by aggradation and progradation occurred rate of s e a l e v e l rise
is d e m o n s t r a t e d
by the
I) facies belts are d i p p i n g towards the deep Depocenters of the i n t e r m e d i a t e ramp, namely display a progressive shift t o w a r d s the h i n g e
following:
ramp (Fig.63). oolite bodies, l o c a t e d in the
north. 2) S p i l l o v e r and w a s h o v e r d e p o s i t s (thick-bedded alternations) indicate a hingeward, onshore storm transport of lagoonalb a r r i e r s e d i m e n t s . A l o n g the v e r t i c a l , t h i c k - b e d d e d a l t e r n a t i o n s overlie
thin-bedded
3) Deep
ramp
alternations
associations
overlie
(Fig.68). shallow
ramp
facies
(Fig.69).
%/ ~5
vF0 w
Fig.68 thin-bedded
Overposition alternations.
of thick-bedded alternations over R i g h t : s e c t i o n # 7 ; l e f t : s e c t i o n #20.
125
3(
2C
IC
m0
Fig,69 A~B Stratigraphic section #15 showing gradual supplantation of intermediate and shallow ramp by thick Lithiotis banks, C Transition from shallow ramp to intermediate-deep ramp (section ~5: oncolite packstones and grainstones --> s k e l e t a l wackestones --> lime mudstones --> Lithiotis bank, m
126 The transgressive t r e n d w a s m a r k e d by s t e p w i s e p h a s e s w h i c h led to 7 m t h i c k l i t h o f a c i e s assemblages which differ depending of the p o s i t i o n on the s u r f a c e of the ramp. The a
sedimentary
w e d g e a n d the of the r a m p SHST formation.
retrogradation
the
TST
and
transgressive trend resulted from t o w a r d s the h i n g e , namely during
Differential,rotational subsidence, played an w h i c h is s u g g e s t e d , o t h e r t h a n by local t e c t o n i c features which may have b e e n local in e x t e n t ,
important role synsedimentary by the lack of
< ,Hinge
Q ~~~lFlexure
~~ Q
ill
hallowing- upward trend
/~_..:.~"~Ret rogradat ion of the sill - Deepening-upward .trend
(D Fig.70 - Progressive of sills,secondary towards
the
hinge.
deformation responsible for the f o r m a t i o n trough areas and shift of the flexure
127
parallelism between time lines (Fig.63),The discontinuous migration of the o o l i t e b a r r i e r followed the direction of m i g r a t i o n of the flexure w h i c h o f f e r e d the optimal b a t h y m e t r i c c o n d i t i o n s for t a n g e n t i a l o o l i t e f o r m a t i o n , T h e t e c t o n i c t i l t i n g determined a progressive f o l d i n g and shift of the flexure towards the hinge (Fig.70), This determined a differential deformation and downwarping b e t w e e n f l e x u r e and hinge r e s p o n s i b l e for the f o r m a t i o n of I) a
®
®
® 1
10
.'5
my
my
,,10
Sill
Secondary trough
128
East
10m
30m
~E NW 7
J tithlotls wackestones
"" " ' ' *
...............
oncobiosparrudite
~. ~ ' : :
/A
5
,.~;
,../j
oospsrite
~:====c=--=,'==ml0m~ "V/~
~0
biosparite |it hioti$ wackestone
F i g , 7 1 - E x a m p l e s of s i l l s e q u e n c e s a n d b e d d i n g s t y l e s of the sill a r e a . In t h e example below the accentuation of channel traces (transitions from flattened to s e m i c i r c u l a r scours) is s e e n as t h e r e s u l t of a p r o g r e s s i v e uplift and transformation of
a former
deep
ramp
floor
into
a sill,
129
secondary trough in the north d i s t r i b u t i o n ; and 2) sill sequences.
that
complicated
facies
Some examples of sill sequences are given in Fig,71. The f o r m a t i o n of a s e c o n d a r y trough and sill s e q u e n c e s are seen in terms of p r o g r e s s i v e increments and decreases of v e r t i c a l space c o n s e q u e n t to the d i f f e r e n t i a l tectonics (Fig.gO).This mechanism is explained by the model of relief inversion d e s c r i b e d in c h a p t e r #A. The interbedding of lime mudstones with deeper ramp lithofacies, especially recorded in the shelf margin facies tract, may have been p r o d u c e d by u p l i f t s of the p l a t f o r m w h i c h c a u s e d the e m e r s i o n of some areas. Fig.72 shows for e x a m p l e a t i l t e d s u b s t r a t e s u t u r e d by lime m u d s t o n e s .
F i g . 7 2 - T i l t e d beds o v e r l a i n by d m - t h i c k lime m u d s t o n e s . The tilting produced emersion of the interface which became a swamp. This is a small-scale example of relief inversion (chapter #&).
D e v o n i a n c a r b o n a t e platform C a r n i e Alps Italy
Introduction
Devonian limestones in the C a r n i c A l p s occur along a 20 K m e a s t - w e s t t r e n d as f a u l t e d t e c t o n i c t h r u s t s ( F i g . 7 3 ) resultin~ from the complex Hercynian and A l p i n e t e c t o n i c p h a s e s (Vai,
............
C O G L I A N S - CO LLINETTA '.
CIMA
t.
O M B L A D E T ~ ~ . ~
Sappada
~ Comeg[ians
".'C.
.......
~
_
...... ~ . . ~ : : ~ ~::~ Km 0 1 0
c Tarvisi(~;
Fig,73 - Location of the study area and outlines of the hercynian tectonic sheets (Venerandi Pirri,1977).The panoramic view shows the Cima Ombladet t e c t o n i c s h e e t in the c e n t e r a n d the C o g l i a n s - C o l l i n e t t a s h e e t in the r i g h t e m b e d d e d w i t h i n the turbiditio Hochwipfel Formation.
131
1980).They a r e p a r t of an e p i o c e a n i c shallow-water carbonate complex i n c l u d e d in a c o n t i n u o u s sequence f r o m the C a r a d o c to the W e s t p h a l i a n . T h e s t r a t i g r a p h y , tectonics and paleontology of the P a l e o z o i c of the C a r n i e A l p s w e r e e x t e n s i v e l y studied. A r e f e r e n c e list is f o u n d in V a i ( 1 9 8 0 ) . A hypothetical c r o s s s e c t i o n of the C o g l i a n s Collinetta reef complex, l o w e r to M i d d l e Devonian, was constructued by Vai (1980) a n d is s h o w n in F i g . 7 A . H o w e v e r w r o n g ( b i o h e r m a r e a s a r e overrated),such a c r o s s s e c t i o n is u s e f u l as it e m p h a s i z e s the well pronounced progradat iona i trend that characterized the platform growth during that time interval.
w
E
mo- ~
1200
-
i
-
m0
1000
Fig,74 - C r o s s
s e c t i o n of the C o g l i a n s - C o l l i n e t t a reef complex (from Vai,1980).TF:tidal flat; BR: Back-reef area~IR: inter-reef area; BI: Bioherms; FR: Fore-reef area9 PR: Peri-reef area. The stratigraphic Frasnian in age, water complex.
sequence forms the
described uppermost
here,Givetian part of the
to U p p e r shallow -
The paleoenvironmental situation of adjacent areas of the Coglians-Collinetta shallow-water complex is simple, as is exemplified by the stratigraphic sections measured in the Volaia-Coglians (Fig.75).These five stratigraphio sections i n d i c a t e a d e p o s i t i o n p a s s i n g f r o m a r e e f f l a t in the e a s t to a tidal or storm flat (Wanless,et ai.,1989) in the west.The general vertical and westward trend is fining-upward and shallowing-upward. Grain sizes show a westward decrease from 0 p h i to 4 p h i . T h e f o s s i l c o m p o s i t i o n s h o w s a c h a n g e f r o m open, agitated environments (corals, algae, brachiopods,foraminifers, (Amphipora, etc.) to semirestricted, protected conditions
calcispheres,ostracods).
132
133
/
/
3 N
16
2(
• ....
•..:~.:
D'
. .. ,...
1
10-
10-.}....
).:/..; .,..:.
1
• ,'~ -.t.[
- i}/0~
'.-...
:~.~, ,: .,'.,, mO
m(
mO
~",,,' •"
Fig,75 Cross section of M.Volaia-Coglians shallow-water complex showing vertical and landward shallowingand thinning-upward trends.(Section#~ m e a s u r e d by A , A r g n a n i ) . A~6.[ : m a s s i v e b e d s c o m p o s e d of c o r a l r u b b l e ( o u t e r r e e f flat; s e c t i o n #5).B~B':Sigmoidal calcarenite beds probably developed as sandwaves ( s e c t i o n fl3),C~C': i n n e r l a g o o n and t i d a l - s t o r m flat ( s e c t i o n s #1,2),
134
J REEFFLAT
I
DEEP.INTERMEDIATERAMP I 5 2 1 • •
4
.3
30-
I SHALLOW RAMP I 100m
20-
6
]ntraclast shoal 3
Pond
!:~':::V:A
~:~...
4
Open lagoon N
10-
Brachiopod bar
N
Reef flat
g
?-: ,... -"~. mONE
SW
101
m 5
o
I
I
I
I wackestone
packstone
1
Fig.76 - Stratigraphic sections of t h e C i m a O m b l a d e t succession and (below) oros section of t h e F l o r i d a platform (Enos,1977) which shows analogous vertical and lateral sediment trends,
135
T h e s e c h a n g e s w h i c h a l s o o c c u r a l o n g the s t r a t i g r a p h i c sections are related to a predominating progradational trend. The sedimentary i n t e r f a c e w a s i n c l i n e d t o w a r d s e a s t a n d s u b j e c t to flooding by storm currents.The physiography and sediment distribution are comparable to a 'Motu-Hoa' configuration (Bourroulh-le Jan and Talandier,1985) where onshore directed storm floods loose gradually energy and competence towards inner areas, w i t h the f o r m a t i o n of a s h o r e w a r d fining-upward grain size trend. The Cima Ombladet carbonate succession displays remarkable differences in facies organization with respect to those occurring in coeval, adjacent parts of the shallow-water limestone complex. These dissimilarities were superficially explained (Galli,198A,1985) as a r e s u l t of a d e p o s i t i o n within an i s o l a t e d a t o l l w i t h i n a m a j o r c a r b o n a t e c o m l p l e x . Such differences m a y be b e t t e r explained by Cima Ombladet succession as having formed intrashelf ramp structure.
considering the as an onlap,
In t h e C i m a O m b l a d e t carbonate succession a transition from a reef flat to semirestricted, inner lagoons is recorded (Galli,198A; 1985a,b,c; 1986). The paleobathymetry (Fig.77), reconstructed by m e a n s of i n t e g r a t i o n of s t a t i s t i c a l a n d f a c i e s a n a l y s e s , c o n s i s t s of a s e r i e s of l a g o o n s s e p a r a t e d by i s l a n d s a n d b a n k s w h i c h c o m p l i c a t e the e n v i r o n m e n t a l trends. Environmental gradients w e r e s t u d i e d by m e a n s of q u a n t i t a t i v e m o d a l a n a l y s e s of p a l e o n t o l o g i c a n d l i t h o l o g i c c o m p o n e n t s of 76 thin sections. F r o m t h e l e f t to t h e r i g h t s i d e of the d i a g r a m of F i g . 7 7 A the increase in o s t r a o o d s , calcispheres a n d Amphipora p e r c e n t a g e s corresponds to a t r a n s i t i o n f r o m the o u t e r r e e f - d e e p r a m p to shallow ramp sectors. The decrease in s e d i m e n t a r y i n f l u e n c e of the outer-inner reef flat towards the shallow ramp is gradational.For each lithofacies the a v e r a g e fossil abundance was correlated with the corresponding detritus:matrix ratio (biopeloidal + intraclast detritus : matrix + cement). This r a t i o , b e i n g a m e a s u r e of the p a c k i n g , g i v e s an e s t i m a t e of the environmental energy (Fig.77C).With the e x c e p t i o n of c r i n o i d s and some stromatoporoids, inverse correlations between fossils and detritus:matrix ratio indicate that organisms lived in (StrinEocephalus burtini, muddy habitats. Brachiopods Pentamerus) l i v e d in the d e e p ramp, p r o b a b l y in a s e r i e s of
136
80-
.-.-..a
~'"
b •
CRINOIDS
•
8RACHIOPOO$ TRYPANOPORA
js
.
g |:?:", 0
-... ".':*
t.
•
THAMNOPORA
O
AMPHIPORA
*
OSTRACOO$ & CALC$$PHERES
. ,.. ~.
....
:o '~
....
1 ~"'"
** °..
7
"'"
_
"'" 0
.1
.9
DETRITUS/ MATRIX
DETRITUS
I MATRIX
REEF FLAT
BIOPELSPARITES
DEEP
BIOMICRITES
RAMP
INTERM. RAMP
INTRASPARITES SHALLOW RAMP
MICRITES i
i
i
i
!
t
i
*
i
i
I
i
*
t
i
i
i
SIMILARITY
-
STROMATOPORA THAMOPORA GASTROPODS E A ONCOLITES DETRITUS CEMENT CRINOIDS B BRYOZOANS ALGAE TABULATES AMPHIPORA C SPONGES CALCISPHERES * MUD MATRIX OSTRACODS " ~D BRACHIOPODS TRYPANOPORA
137
A ,.,
f.' I.
•
,
"
.
[ ;"~ [ ". "REE'F'" • "
'
"
'
"
B
B
'
A
SHALLOW \
~
"
"~
RAMP
RAMP
D
C
"" " ' " • • "
--: :L
REEF
Q-MODE CLUSTERS
3B
3A
::::::::::::::::::::::::::::::
BATHYMETRY
2B 2A
:
.....
5 i
RAMP
7B
...........
7A ...... :.::~
8. ,~ !0. .
i
9
~ : ~
::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::: :::::::5:::;5i:.':; "-5: :::: :}:):: :i:!:}:::: :-::2 : ::::::::::::::::::::::::::::::::::::::
R- MODE CLUSTERS D:M RATIO
1
FLAT
B
A
D
C
11 O
FOSSIL 96
so] / O
FOSSIL DIVERSITYs 1
\
0
Fig.77 Paleoenvironmental reconstruction and facies distribution of t h e C i m a Ombladet carbonate succession (for more details see Galii,1985), paleobathymetry, petrographic trends and Q,R-mode clusters.
138
tidal c h a n n e l s and bars c u t t i n g t h r o u g h inlets, Trypanopora lived in the deep ramp. The development of Thamnopora was confined to the i n n e r reef flat and the intermediate ramp. C a l c i s p h e r e s and o s t r a c o d s lived in the s h a l l o w r a m p . T h e R - m o d e c l u s t e r i n g (Fig.77D) g i v e s four c l u s t e r s r e p r e s e n t a t i v e of the o u t e r reef flat (B), inner reef flat (A), deep ramp (D) and s h a l l o w ramp (C).No d i s t i n c t i v e faunal a s s e m b l a g e c h a r a c t e r i z e s the i n t e r m e d i a t e ramp. I m p o r t a n t t r e n d s t o w a r d s the s h a l l o w ramp are: I) a d e c r e a s e in fossil d i v e r s i t y ; and 2) a d e c r e a s e in the detritus: matrix ratio (Fig. V 7 B ) . T h e s e trends are peculiar features of i n t r a s h e l f ramps. O t h e r b e a c h profiles, not d e v e l o p e d in onlap ramps, d i s p l a y o p p o s i t e trends, such as the e x a m p l e shown in Fig.78 (Auernig Formation, Permian - Carboniferous, eastern Carnic Alps, Italy: G a l i i , 1 9 8 6 ) . As seen f r o m the m e a s u r e d sections, faunal and lithofacies variations form reef flat to inner lagoon are rather complicated and evidence for a facies mosaic, Based on microfacies and litho!ogic composition, twelve facies were recognized (Galii,1985). The h y p o t h e t i c a l map showing the g e n e r a l facies zonation is shown in F i g . 7 7 A ( G a l l i , 1 9 8 5 b ) . The r e c o n s t r u c t e d e n v i r o n m e n t a l s e t t i n g b e a r s a g e n e r a l s i m i l a r i t y to some s i t u a t i o n s o c c u r r i n g in the E x u m a Cays~ w h e r e o p e n lagoons and b e a c h e s form just close to reef flat l o c a t e d l e e w a r d and tidal inlets (Fig.79). A peculiar feature occurring in the study area is the o c c u r r e n c e of m a s s i v e beds c o m p o s e d of i n t r a c l a s t g r a i n s t o n e s and d o l o i n t r a m i c r u d i t e s . The grain s o r t i n g is m o d e r a t e to poor. The p a c k i n g is low. I n t e r n a l sedimentary structures are first order low-angle cross-bedding and second order high-angle d i p p i n g f o r e s e t s w i t h i n first o r d e r s e t s . T h e s e beds h a v e been r e g a r d e d as the lagoonward terminations of the reef flat occurring as l i n e a r sand r i d g e s . T h e s e b o d i e s h a v e some a n a l o g y with r a m p a r t d e p o s i t s o c c u r r i n g in the reefs inside the Great Barrier Reef (Scoffin,1977). B r a c h i o p o d s are the m o s t a b u n d a n t f o s s i l s in the s u c c e s s i o n as occurr in a wide range of subenvironments, As is shown schematically in F i g . 8 0 , d i f f e r e n t biostratonomio data of these fossils c h a r a c t e r i z e the three sectors of the ramp.
139
BANK
BAR,RIDGE
...............
Ostracods
I~ JI} I~ p 2 ~
~
[
Gait ropod,~
Calci.~pherae Philloid algae
I
J
Antrachoporella Tubiphytes Epimastopora Eugonophlllum Crinoids Fusulinae
Bryozoans Faunal diversity
J
Detritus : matrix Fi~.78 - Allochem distribution in Auernig Formation ('Permo-Carbonifero Italy: G a l i i , 1 9 8 6 )
Facies
ramp consists alternations.
beach profile in the Pontebbano, Carnie Alps,
associations
Shallow
The shallow thick-bedded
a
of
ramp
pond
facies
and
thin-
and
140
141
DEEP
~
INTERMEDIATE RAMP
SHALLOW RAMP
HOMOGENEOUS
HOMOGENEOUS
HETEROGENEOUS
RAMP (BAR)
FAUNAL COMPOSITION
HOMOGENEOUS
DISSOCIATION OF SKELETAL PARTS
VALVES ARTICULATED VALVES BOTH (DISARTICULATED ARTICULATED & FOR BURROWERS} DISARTICULATED
VALVES BOTH VALVES NEARLY ARTICULATED & ALL DISARTICULATE D DISARTICULATED
ORIENTATION
LIFE POSITION, PARALLEL
IMBRICATED, INCLINED, PARALLEL
RANDOM
RANDOM
PACKING
LOW
HIGH
VARIABLE
HIGH
GEOPETAL INFILLING
INTRAMICRITIC
INTRAMICRITIC
INTRACLASTIC. NONE
BIOPELOIDAL
BRACHIOPOD
ASSEMBLAGE
66
"IN SITU"
78
90
LOCALLY TRANSPORTED TRANSPORTED
29
TRANSPORTED
Fi~.80 - Biostratinomy of b r a c h i o p o d s . Brachiopods f o u n d in the deep ramp represent an 'in situ' a s s e m b l a g e , as is s h o w n by s h e l l s f o u n d in l i f e p o s i t i o n , articulated and floating in a micrite matrix with a micrite geopetal infilling. Brachiopods of sublittoral bars in the deep ramp underwent a local selective transport, by means of tidal-longshore currents (bipolar beddings). Brachiopods occurring in the i n t e r m e d i a t e and shallow ramp (within thin- and thick-bedded alternations) are smaller, display a higher degree of transport (random orientations,a greater fragmentation, and various geopetal infillings). Brachiopods piled up in t h e intermediate ramp underwent a mass transport, as is evidenced by random orientations, poor sorting and variable packing. Unlike brachiopods of the d e e p ramp, those of the intermediate and shallow ramp underwent transport and mixing with other lagoonal f o s s i l s (see F i g . 1 3 for s o m e a d d i t i o n a l d e t a i l s ) .
142
Pond
facies
Description This facies consists of poorly fossiliferous, well-bedded, thin, black micrites and barren dolomicrites, with scarce calcispheres, o s t r a c o d s and Trypanopora ( G a l i i , 1 9 8 5 ), and v e r y thin s h e l l e d b r a c h i o p o d s . Pyrite, organic matter horizons and rare algal mat w i t h m m - s i z e l a m i n a t i o n s o c c u r . 0 t h e r s e d i m e n t a r y s t r u c t u r e s include v e r t i c a l burrows, some w a v y lamination, flat p e b b l e c o n g l o m e r a t e levels and p e b b l e clusters. I n t e r c a l a t e d w i t h this facies are t h i n - b e d d e d and t h i c k - b e d d e d alternations. The last consist of bioclast interlayers of v a r i a b l e t h i c k n e s s . R a p i d p i n c h - o u t s into m i c r i t e facies can be seen in some instances.The faunal content is h e t e r o g e n e o u s . I n t r a c l a s t s of v a r i a b l e s h a p e s c o n s i s t of b l a c k m i c r i t e s . T h e s e beds are organized into a fining-upward sequence which is composed of two units: I) a lower part, consisting of d a r k calcarenitic beds, composed of b r a c h i o p o d s , c o r a l s , crinoids, calcispheres, p e l o i d s and i n t r a c l a s t s ; and 2) an u p p e r part, composed of t h i n n e r beds with disarticulated both thin- and thick-shelled brachiopods. This u p p e r part g r a d e s q u i c k l y into c a l c i l u t i t e s w i t h thin algal laminae. Interpretation A very s h a l l o w e n v i r o n m e n t for this facies is i n d i c a t e d by vertical burrows , p a u c i t y of f o s s i l s , a l g a l layers and p y r i t e horizons.This facies represents intertidal pools and ponds whose extension and depth depended on the local intraclast shoal c o n f i g u r a t i o n , and o t h e r t o p o g r a p h i c b a r r i e r s . T h i c k - and t h i n - b e d d e d a l t e r n a t i o n s represent a deposition by storms, as w a s h o v e r d e p o s i t e d , as e v i d e n c e d by the f o l l o w i n g : sharp basal c o n t a c t s , c o u p l e t s of s h e l l y layers and l a m i n a t e d mud, grading, escape structures in the underlying mud and screening fabrics.The tripartite subdivision of the thick bedded alternations is a n a l o E o u s to that o c c u r r i n g in F l o r i d a Bay. Intermediate
Intraclast
ramp
shoal
Description This f a c i e s c o n s i s t s of p o o r l y grained intraclast grainstones
sorted, disorganized, and packstones, up
coarsely to 3 m
143
thick.Lithoclasts are of v a r i a b l e s i z e , s h a p e and c o m p o s i t i o n . Fossils are all transported and of variable provenance (lagoons, reef flat, p o n d s ) . C o m m o n sedimentary structures are vadose silt,cut-and-fills, keystone vugs, gradations, crossb e d d i n g and f l a t - p e b b l e c o n g l o m e r a t e s . This lithofacies is overlain by cryptalgal laminites, represented by light-gray, well-sorted, planarbedded, laminated intrasparites, 60 cm to 1 m thick, w i t h very thin micrite laminae, w h i c h are u n d u l a t e d , slightly inclined and stylolitic, w i t h a h o r s e t a i l f i l i g r e e pattern.
Interpretation The i n t r a c l a s t shoal facies r e p r e s e n t s a d e p o s i t i o n in a b e a c h environment,as is i n d i c a t e d by the o c c u r r e n c e of flat p e b b l e conglomerates,fringing cement, keystone rugs, vadose silt, occurrence of v a r i o u s textures and a b s e n c e of a grain size s i g n a t u r e (Davis,et a i . , 1 9 7 2 ) . The o c c u r r e n c e of w i d e t e x t u r a l and g r a i n - s i z e ranges, disorganized beds and m a s s i v e bedding indicate a d e p o s i t i o n u n d e r c o m p l e x h y d r a u l i c c o n d i t i o n s , as a result of island shifting. Cryptalgal laminites are interpreted laminations. The s e d i m e n t was d e p o s i t e d by c u r r e n t s b y - p a s s i n g ridges and bars.
Deep
Brachiopod
~rainstones
as storm
beach-ridge floods and
ramp
and w a c k e s t o n e s
Description B r a c h i o p o d w a c k e s t o n e s c o n t a i n a b u n d a n t m o n o t y p i c a s e m b l a g e s of (StrinEocephalus, Pentamerus) thick-shelled brachiopods o c c u r r i n g t o g e t h e r w i t h s m a l l e r a m o u n t s of other fossils such as crinoids, and o c c a s i o n a l s o l i t a r y corals. Brachiopod grainstones consist of brachiopod shelly layers containing well-sorted shells. This unit ranges in t h i c k n e s s from 1.5 to as much as 3 m. I m b r i c a t i o n s , geopetal structures,
144
planar and bipolar cross-bedding were observed in some instance. Some of the t h i c k e r beds c o n t a i n a g r e a t e r p e r c e n t a g e of i n t r a c l a s t s , a lesser p e r c e n t a g e of b r a c h i o p o d s , a n d a lesser shell o r i e n t a t i o n .
Interpretation Brachiopod wackestones represent a deposition in a m a r g i n a l bay. The e n v i r o n m e n t is s u b t i d a l , a s s h o w n by the o c c u r r e n c e of p a t c h y and d i s t i n c t , " i n p l a c e " a c c u m u l a t i o n s of b r a c h i o p o d s and o t h e r types of fossils. Zonations of e n d e m i c populations and t e x t u r e s i n d i c a t e that this l a g o o n was r a t h e r large and deep. Brachiopod grainstones may be r e f e r r e d to 'in situ' lagoonal bars and b a n k s . S o m e r e w o r k i n g by s t o r m a g e n t s is e n v i s a g e d for the t h i c k e r beds, w h i c h may r e p r e s e n t r e w o r k e d lagoonal bars and banks close to the intermediate ramp which was h e t e r o g e n e o u s in c o m p o s i t i o n .
~positiona!
model
The measured stratigraphic section records complex and recurring facies transitions.The paleoenvironmental reconstruction is shown in Fig.21 (Galii,1986). The Markov chain analysis (Miall,1973),applied to the succession (Galii,1985) in o r d e r to d i s c r i m i n a t e d e t e r m i n i s t i c from r a n d o m facies t r a n s i t i o n s , w a s an aid in the i d e n t i f i c a t i o n of two m a i n s e q u e n c e s c o r r e s p o n d i n g to: I) a s t o r m 2) a b e a c h
bar bar
sequence; sequence.
and
These two sequences (Fig.81) are the result opposite,different d e p o s i t i o n a l m e c h a n i s m s w h i c h were in the area: I) a g g r a d a t i o n ; and 2) p r o g r a d a t i o n .
of two operating
The c o m p l e x i t y of facies t r a n s i t i o n s , s h o w n by the r h y t h m o g r a m of F i g . 8 2 , i s a c o n s e q u e n c e of the i n t e r f e r e n c e between these two d e p o s i t i o n a l m e c h a n i s m s . The p r o g r a d a t i o n a l trend produced the d e p o s i t i o n of s h a l l o w water deposits over deep ramp facies. As indicated by the detailed microfacies analyses (Galii,1985) these shallow-water s e d i m e n t s p r o g r a d e d into the lagoon, from reef flats as l i n e a r
145
OPEN LAGOON . . . . . . . . . . "> BIOCLAST BAR ° o"~
o
POND FACIE~
°.•
oO°• o.
~.~
..."
POND .." V ..... -'9 FACIES INTRACI_AST . . . . . . . . . . . "> CRYPTALGAL ......... SHOAL < . . . . . . . . . . . . LAMINITE
Pond
Pond
Cryptalgal
3 -
Cryptalgal laminite
laminite 3 -
nkJ 2'"2- ~ .'--I Bioclast
2 -
~a~ calcareous g y p s u m and algal laminite--->massive selenite---> banded selenite--->chaotic gypsum (pebbly m u d s t o n e ) --->slump breccia (megabreccia), A great proportion of the banks is r e p r e s e n t e d by m e c h a n i c a l l y reworked gypsum which underwent a basinward transportation by debris flow mechanisms in a subaerial environment, The authors proposed an autocyclic cannibalistic process whereby gypsum was eroded from the margins and redeposited basinward, The m e c h a n i c a l deposition was thought to have been the result of lowering sea-level c a u s i n g a d e p o s i t i o n a l regression, The modal cycle can be split into two parts: a lower aggradational cycle (black shales to a u t o o h t o n o u s and b a n d e d selenite), overlain by an u p p e r coarseningand thickeningupward cycle represented by allochtonous gypsum, The same organization is v i s i b l e at a m e g a s e q u e n c e scale. This modal cycle is t h e r e f o r e a n a l o g o u s to the modal sequence described above, An a l t e r n a t i v e i n t e r p r e t a t i o n to a p u r e l y a u t o c y c l i c a l model of s e d i m e n t a t i o n w o u l d be a c a n n i b a l i s t i c t e n d e n c y r e s u l t i n g from the o v e r s t e e p e n i n g of the relief due to a t e c t o n i c inversion. This c a n n i b a l i s t i c trend was c o n c o m i t a n t w i t h a r e t r o g r a d a t i o n of the c a n n i b a l i z e d margin.
254
250
0
250
0
2~
PALEOCENE j a-i li!
.lOC 6
135
i
~0 q Z
145
~5 150 ~0 ~55
25 o
150
z
30 w
~5 40
-=
U
_
w
~65
/
z o
/
z ~
/
~
/
I
I
/
/
/
/
%
"~ ~ ~
~
m
0
/
/ I
m
0
1
/
0
/
/ /
I
/
/
I
?
-m
:2?.
r~
0
.,4
/
/
/
.1~ ,-4 .-~ ,-4 0
=
.~ ,4
I
D
~
,,~
,-~
0
~,,~. o
N.o
½
"'
/ /
~) 4-}
I
~7"
S
o
..I
???? ??
o~
.,-4
°~o~
~::!i. .i:p / I / /
_
~ili~
}ii,~:~
I
0 ~ ,-~ 0 0 D
~ m
~
r~
~
0 4-I
I
/ /
o
! .-.I
QI
268
HOCHWIPFEL
m
I
F.
PELAGIC LIMESTONES
I SLOPE CARBONATES
F~q CT7
SHALLOW- WATER FORMATIONS
F PLATFORM
BASIN
! f
I
/ f
269
crisis and extinctions attributed by Mclaren (1970) and Playford, et aI.(198~) to a b o l i d e impact. In the C a r n i e Alps the d r o w n i n g is r e c o r d e d by the d e p o s i t i o n of s h a l l o w - w a t e r p e l a g i c limestones. Tectonics became progressively important,as early as the Frasnian,when intrashelf onlap ramps were formed. In the Dinantian the deepening-upward trend was accentuated as a result of the fragmentation of the p l a t f o r m by e x t e n s i o n a l tectonics. Neptunian dykes, olistoliths, olistostromes, sedimentary hiathuses and unconformities evidence for the sedimentary tectonics. The cross section evidencing the g e o l o g i c a l e v o l u t i o n of the p l a t f o r m (Spalletta, et ai.,1979; Fig.157) contains several features common to o t h e r platform margin transitions subjected to extensional tectonics and successive relief inversion such as: I) coarsening-upward trends of m e g a b r e c c i a s 9 2) d i v e r g e n t w e d g e s of p e l a g i c - b a s i n a l s e d i m e n t s at the m a r g i n of the p l a t f o r m 9 and 3) s y n s e d i m e n t a r y faults. The hercynian synsedimentary tectonics is evident from an e x a m i n a t i o n of the fence d i a g r a m of Fig. 158 w h i c h reveals a horst-graben geometry. Angular unconformities amounting to 10°-20 ° s e p a r a t e some of the p e l a g i c F o r m a t i o n s . Two r e c u r r e n t types of d i s c o r d a n c e s can be o b s e r v e d in the study area. A first type consisting of fan-shaped discordances was the product of a r o t a t i o n a l , basinward tilting.The second, more complex, was p r o d u c e d by b a s c u l a t o r y m o v e m e n t s or i n v e r s i o n s in the direction of tilting which may be related to relief inversion mechanisms. The d e v e l o p m e n t of the s t r a t i g r a p h i c s e q u e n c e was c o n t r o l l e d by strike-slip tectonics from the U p p e r Devonian to the L o w e r Carboniferous,consequent to the activation of a transform s y s t e m w h i c h d e t e r m i n e d a w e s t w a r d drift of c o n t i n e n t a l blocks s e p a r a t e d by n a r r o w seaways. The c e n t r a l areas of the h e r c y n i d e s display arched structural p a t t e r n s , d o m e - l i k e features, a b s e n c e of o p h i o l i t e s , w i d e s p r e a d high-temperature metamorphism and a g r e a t number of g r a n i t e intrusions which evidence for r a i s e d isotherms and thinned continental crust. No o c e a n i c crust was present untill the Upper Devonian.The absence of o p h i o l i t e s , nappe structures, island ares and a lack of h i g h - p r e s s u r e metamorphism in the h e r c y n i d e s led Krebs and W a c h e n d o r f (1973) to infer a d i a p i r i c o r o g e n e s i s as an a l t e r n a t i v e to a p l a t e t e c t o n i c model. Vai and Cocozza (1986) sustained that the deformation, p r o g r e s s i n g from west to east, was c o n t i n u o u s and d i a c h r o n o u s
270
N
%
ALPINE
FAULTS
2o
w
E HERCYNIAN
,o°1
1
JOINTS
JI
S t
2
3
• 4
I 5
Fig.159 - Right. Equiarea! projection showing the angular relationships b e t w e e n 'Riedel shears' (I), m a s t e r faults (2), tension gashes (3), sigma 1 (~) and sigma 2 (5).Left. Canale-Volaia thrust sheet. Percent distribution versus direction of the b e a r i n g s of IA7 a l p i n e faults and of A2 h e r c y n i a n s y n s e d i m e n t a r y d y k e s and p a l e o f r a c t u r e s . in the H e r c y n i a n Belt; the d e f o r m a t i o n p h a s e s are d a t e d to the f o l l o w i n g periods: 350 m,y. (Breton phase); 315 m,y. (Sudetic phase); and 300 m.y. (Asturic p h a s e ) . A c c o r d i n g to this s c h e m e the S u d e t i c p h a s e did not a f f e c t the C a r n i c Alps. In the s t u d y area the p e r c e n t d i s t r i b u t i o n of a2 s t r i k e s of tension joints, p a l e o f a u l t s , s e d i m e n t a r y dykes gives two modal directions (N 30 ° E; N 150 ° E) w h i c h r e p r e s e n t R iedel p l a n e s ( W i l c o x , e t a i . , 1 9 7 3 ) , as shown in the e q u i a r e a l p r o j e c t i o n of Fig.159.The compressive hercynian and Alpine phases only p r o d u c e d a s t a t i s t i c a l r e m o b i l i z a t i o n of this joint system, as r e s u l t s from a c o m p a r i s o n b e t w e e n the p e r c e n t d i s t r i b u t i o n of hercynian paleofractures and that of I~7 alpine faults occurring in the same thrust sheet, At an e a r l y stage of wrenching a 'dog-legged' graben structure (Illies,1981) d e v e l o p e d from an e c h e l o n s y s t e m of s t r u c t u r e s as a c o n s e q u e n c e of m o t i o n of f i r s t - o r d e r s h e a r zones and N 3 0 ° E s e c o n d - o r d e r shear. R i e d e l shears i n i t i a l l y f o r m e d u n d e r a low rate of axial shear motion; upon individuation, faulted blocks were s u c c e s s i v e l y r e m o b i l i z e d and a c t e d as h i g h - a n g l e s h e a r planes.
271
\
,,
FLOWER
STRUCTURE
INTERPRETATION
¢ SSW
NNE
[/I,'-,,,.,%.:,,,, "/~~~~/.",~' " ""': ,v ,~",:.~ti,-,~r~-~:'"'iQ~'.'~,~i.ll~"~" :~" '~'~ '"'
0
I~',
1000
""
2000
OLEODOTTOTAL (PSO MONTECROCECARNICO)
H _.:"-"/
"?,
. ,. ,Li! ---h---~.~.c.,,.
~\
",,
N
S
MG 2000
\ m
~ U D
""
29-,¢O m
RIO SELEIT
14.0
SW
272 CJMA OMIILADET
SASSO NERO
MD
H
M~
N
UD N
"
N
CIMA OMBLADET UD
UD
~ . . . . . . . . . . / " ' "
1 KM
CRETA DI 2250
-
WNW
....
COLLINETTA
M
D
~
D
C~U_ON ~ ~ ' ~ , . ~ . ; ( ~ 1500
LD
~
~
~
D
_ .
x
~,~::::p.,uo
H
~
. ....
/
-.,.... ........ .-~ ....
,
.~\.~....
FRAUENHOHE MD
,
.....
.
"
Y
~
NNE
273
F i g . 1 6 0 - E x a m p l e s of fold s t r u c t u r e s in the P a l e o z o i c of the C a r n i c Alps. A: P . s o di M . C r o c e C a r n i c o (Cantelli et a i . , 1 9 6 8 ) . An a n t i c l i n a l structure,however dismembered into slices, is clearly recognizable in the p r o f i l e . T h i s cross section was p r e v i o u s l y i n t e r p r e t e d as a series of i m b r i c a t e d t h r u s t sheets. Above :interpreted flower structure. B:Panoramic view towards east of the P.di T i m a u from P i z z o C o l l i n a (from C a n t e l l i , et ai.,1982) showing the southern limb of an anticlinal s t r u c t u r e close to the h i n g e area..C: H i n g e of an a n t i c l i n a l structure, overprinted by alpine tectonism (Spalletta, et al.,1979).D~E: Cima 0mbladet and Sasso Nero (see Fig.73), interpreted as flower structures. The n o r t h e r n flank of the Cima O m b l a d e t (sketch from H e r i t s c h , 1 9 3 6 ) r e v e a l s c o m p l e x box f o l d s . T h e s t r u c t u r e is u n c o n f o r m a b l y o v e r l a i n by the t u r b i d i t i c Hochwipfel Formation, hence it formed in the Lower Carboniferous. F: A n t i c l i n a l s t r u c t u r e at C r e t a di C o l l i n e t t a (modified from C a s t e l l a r i n , 1965: in D e s i o , 1 9 7 3 ) , interpreted here as a flower structure. G: Small-scale anticlinal and s y n c l i n a l s t r u c t u r e s at F r a u e n h ~ h e , L a g o V o l a i a (Vai,1963) (cf. with A ) . S u r p r i s i n g l y , these folded s t r u c t u r e s (and o t h e r s not shown here) have been ignored or d i s m i s s e d by i t a l i a n a u t h o r s working in the area, who made up a complicated style of i m b r i c a t e d u n d e r t h r u s t sheets (cf.Fig.162) e n g u l f e d w i t h i n the C a r b o n i f e r o u s H o c h w i p f e l Formation. Symbols:H:Hochwipfel Formation; D: D e v o n i a n ; S: Silurian; 0: 0rdovician; UD: Upper Devonian; MD: Middle Devonian; MG: m e g a b r e c c i a s ; LD: L o w e r Devonian~ R: r a d i o l a r i t e s .
274
The s p l a y i n g of the d i v e r g e n t w r e n c h i n g zone in the area was responsible for the n o r t h w a r d b l o c k m i g r a t i o n , retrogradation of fault planes, formation of the fan-shaped angular u n c o n f o r m i t i e s and the d i v e r g e n t p a t t e r n w h i c h can be p e r c e i v e d from an e x a m i n a t i o n of F i g . 1 5 8 . A s u c c e s s i v e stage in the s t r i k e - s l i p e v o l u t i o n in the area led to c o n v e r g e n c e , f o l d i n g a n d r o t a t i o n of f a u l t e d b l o c k s , a n d the disintegration of the b l o c k mosaic leading to d i f f e r e n t i a l block movements and compressive structures squeezed out of a d j a c e n t a r e a s , s u c h as 'flower s t r u c t u r e s ' The second type of discordances visible in the fence diagram of Fig.158 were probably produced during this stage, by b l o c k u p l i f t i n g and relief inversion. The carbonate thrust sheets are intensively deformed and folded, as documented formerly by Heritsch (1936) who i n t e r p r e t e d the t e c t o n i c s t r u c t u r e as a f o l d e d style c o m p o s e d of b r a c h i a n t i c l i n e s and s y n c l i n a l structures. Later, italian a u t h o r s w o r k i n g in the a r e a r e c o n s i d e r e d such an i n t e r p r e t a t i o n and p r e f e r r e d a m o r e s o p h i s t i c a t e d style of m u l t i p l e , stacked thrust sheets enguifed within the flyschioid Hochwipfel Formation.This interpretation did not rule out the o c c u r r e n c e
Fig.161 - Evolution of the flower c o n v e r g e n t w r e n c h i n g ( a d a p t e d from De
structures Smet,198~).
produced
by
275
of f o l d s : t h e r e is no d o u b t in fact sheets are strongly folded (Fig.160). the C i m a 0mbladet (Fig.160), may be structures'
that most of carbonate Some structures,such as interpreted as 'flower
The evolution of the area from the Frasnian to the Lower Carboniferous p r o p o s e d h e r e is s h o w n in F i g . 1 6 1 (adapted from De S m e t , 1 9 8 A ) . W r e n c h i n g i n i t i a l l y l e a d s to f o l d i n g a n d f a u l t i n g of the c a r b o n a t e platform. Successively the anticlinal areas are uplifted and squeezed out, with formation of 'flower structures'.The flower structure concept is a key in the interpretation of s e v e r a l t e c t o n i c s t r u c t u r e s in the a r e a w h i c h display an o p p o s i t e vergence, s u c h as t h e s t r u c t u r e s h o w n in Fig,162, bracketed by arrows,which could be interpreted alternatively as a t h r u s t . A c c o r d i n g to t h e 'flower structure interpretation', compressive phases (Asturic phase) may have reoriented the d e t a c h e d slabs of the c a r b o n a t e platform, or o v e r t u r n e d s o m e b l o c k s or limbs of f l o w e r s t r u c t u r e s .
N
S
f.
DP KmoO
10
Fis.162 - Palinspastic reconstruction of the P a l e o c a r n i c chain (Upper Permian) (after Vai,1976).The s t r u c t u r e of the c h a i n is i n t e r p r e t e d as a s e r i e s of i m b r i c a t e d u n d e r t h r u s t s , O b s e r v e the absence of a n t i c l i n a l forms in the p r o f i l e (cf. with Fig. 160),the opposed vergence of the area delimited by arrows i n t e r p r e t e d h e r e as a ' f l o w e r s t r u c t u r e ' , t h e f a u l t (a) f l o a t i n g w i t h i n the f l y s c h H o c h w i p f e l Formation.According to the t h r u s t sheet view, the volume of the Hochwipfel Formation is preponderant.Conversely, a flower structure interpretation l e a d s to r e d u c i n g s u c h a v o l u m e , i n keeping with stratigraphic data indicating an o v e r a l l total thickness of t h e H o c h w i p f e l F o r m a t i o n of a b o u t 800 m, in c o n t r a s t w i t h the t h i c k n e s s of the c a r b o n a t e p l a t f o r m w h i c h a m o u n t s to a b o u t 1 2 0 0 m. H: H o c h w i p f e l Formation (NamurianLower Westfalian); DPN: neritic-pelagic carbonates (GedinnianVisean)9 S; Silurian carbonates and shales; U:Uqua Formation (Caradoc-Ashgill)~ D;Devonian platform carbonates; Di; D i m o n F o r m a t i o n ( L o w e r W e s t f a l i a n ) .
276
A t e r r e s t r i a l - karst h o r i z o n is s a n d w i c h e d b e t w e e n u n d e r l y i n g pelagic and shallow-water carbonates and o v e r l y i n g turbidite deposits. It c o n s i s t s of s i ! c r e t e deposits and v a r i o u s karst features.Recently, Sch~nlaub, et a i . ( 1 9 9 1 ) studied in great detail this horizon and conclusively demonstrated a karst origin. It was the o b j e c t of much study by i t a l i a n g e o l o g i s t s working in the area, who considered and listed several interesting, alternative possibilities (Spalletta, et a i . , 1 9 8 2 a,b,c,d),which s e r v e d as a s t i m u l u s to w o r k e r s in the area a t t e m p t i n g at m a t c h i n g the o c c u r r e n c e of the karst h o r i z o n w i t h the e x i s t i n g model of g e n e r a l i z e d d e e p e n i n g (of. F i g . 1 5 7 ) . S o m e f e a t u r e s of this h o r i z o n o c c u r r i n g in the s t u d y a r e a are shown and d e s c r i b e d in Fig.163. Interpretations concerning this t e r r e s t r i a l h o r i z o n have been c o n t r a s t i n g , b e c a u s e of the d i f f i c u l t y in r e c o n c i l i n g an u p l i f t w i t h the p r e v i o u s i n t e r p r e t a t i o n of the b a s i n w h i c h a s s u m e d a generalized, deepening-upward trend (Spalletta, et a i . , 1 9 7 9 ) and w i t h the o c c u r r e n c e of some b a s i n a l s e q u e n c e coeval with the t e r r e s t r i a l h o r i z o n and r e p r e s e n t e d by p e l a g i c c a r b o n a t e s (Famennian-Dinantian) o v e r l a i n by deep w a t e r r a d i o l a r i t e s (late Dinantian) and the H o c h w i p f e l , turbidite Formation (Silesian) (Spalletta, 1 9 8 2 ) . T h i s p r o b l e m can be r e c o n c i l e d by a m e c h a n i s m of rotational subsidence which contemporaneously sunk the basinward areas and uplifted the platformward zones which b e c a m e 'flower s t r u c t u r e s ' . The o c c u r r e n c e of a T o u r n a i s i a n to V i s e a n emersion horizon draping the platform contradicts the theoretical scheme of d i a c h r o n o u s d e f o r m a t i o n p r e d i c t e d by Vai and C o c o z z a ( 1 9 8 6 ) . T h e m a i n i m p l i c a t i o n of the o c c u r r e n c e of this t e r r e s t r i a l h o r i z o n is that c o m p r e s s i o n a l B r e t o n i c (top D e v o n i a n ) and S u d e t i c (top Dinantian) phases can not be e x c l u d e d (according to i t a l i a n a u t h o r s o n l y the A s t u r i a n p h a s e - W e s t p h a l i a n - took p l a c e in the Carnie Alps).Mineralizations and k a r s t horizons seem to be located p r e f e r e n t i a l l y upon flower structures (they are a b s e n t in the D e v o n i a n rocks c r o p p i n g out in the A u s t r i a n a r e a ) . T h i s documents a localized tectonic control upon mineralizing agents. The exact origin for these Bretonic and Sudetic phases is obscure.As a matter of fact,the DevonianCarboniferous boundary (corresponding to the B r e t o n i c phase in the C a r n i c Alps) r e c o r d s a w o r l d w i d e emersion, as can be e v a l u a t e d from an e x a m i n a t i o n of the r e s u l t s of the 1986 s y m p o s i u m of A a c h e n on 'Late D e v o n i a n e v e n t s a r o u n d the Old Red C o n t i n e n t ' (Ministry of Econ. A f f a i r s , A d m , o f M i n e s , 1 9 8 6 ) . The
two p h a s e s
correspond
to
short-term
sea
level
falls
in
the
277
PELAGIC GARBONATES HERCYNIAN FLYSCH
• EMERSION
HORIZONS
278
charts by Johnson (1985) and Stille (192A). The emersion corresponding to the Sudetic phase (Tournaisian-Visean) is less recorded in the world~ probably the uplift was less i n t e n s e . T h e u p l i f t is d o c u m e n t e d in s e v e r a l areas, for example, in Poland, A r m o r i c a n M a s s i f and the A p p a l a c h i a n s .
F i g , ! 6 3 - D i s t r i b u t i o n of the e m e r s i o n h o r i z o n and a s s o c i a t e d mineralizations (above: a f t e r S p a l l e t t a , et a i . , 1 9 8 2 ) and some aspects of the shallow-water deposits sandwiched between pelagic carbonates and the turbiditic Hochwipfel Formation (A-E). According to the above scheme the minera!isations developed above pelagic and shallow-water carbonates are confined to a n a r r o w belt trending east-west, which became individuated by r e l i e f inversion mechanisms produced by the convergent wrenching tectonics. A): S i l c r e t e d e p o s i t s c o n f o r m a b l y o v e r l y i n g p e l a g i c c a r b o n a t e s (Sasso N e r o a r e a ) . B ) : L a m i n a r and t u b u l a r bands r e m i n i s c e n t of algal tufas (photo c o u r t e s y of L.Brigo).C__~) : D o l o m i t e layers a l t e r n a t i n g w i t h s c a l e n o e d r i c calcite.D_J_) : L o w - a n g l e l a m i n a t i o n i n d i c a t i v e of a s h o r e l i n e e n v i r o n m e n t . These deposits, in a d d i t i o n to those s t u d i e d by S c h ~ n l a u b , et al.(1991),testify for an e m e r s i o n horizon and u p l i f t of the platform (relief i n v e r s i o n ) . Similar silica concentrations or s i l c r e t e d e p o s i t s o c c u r in o t h e r areas of the e a s t e r n A l p s , f o r e x a m p l e in the D o l o m i t e s , above Ladinian buildups, and in the Hauptdolomite Formation in S w i t z e r l a n d , T h e general aspect of these s i l c r e t e d e p o s i t s is a l s o s i m i l a r to s i l c r e t e s r e p o r t e d by S m a l e (1973) from S o u t h A f r i c a and A u s t r a l i a . In all such situations silicification took p l a c e close to s y n s e d i m e n t a r y faults, c l o s e to a M g - C a b o u n d a r y , in a s h a l l o w environment resulting from s p i c u l a e concentrations.In the H a u p t o d o l o m i t e F o r m a t i o n (i.e. Munt de la Bascha, E n g a d i n e D o l o m i t e ) the site of s i l i c a d e p o s i t i o n was s u b t i d a l (less than 10-20 m deep)~ probably subjected to a syndiagenetic instability (R. Trumpy,1987:pers.comm.).Barite, fluorite, scalenoedric calcite and to a l e s s e r degree, s p h a l e r i t e , are a c c e s s o r y c o m p o n e n t s of the s i l c r e t e d e p o s i t s . T h e o c c u r r e n c e of s e d i m e n t a r y s t r u c t u r e s such as r h y t h m i t e s and the a b s e n c e of c o n t e m p o r a n e o u s v o l c a n i s m rules out an e p i g e n e t i c origin, as h y p o t h e s i z e d by S p a l l e t t a , et ai.(1982), or even a diagenetic transformation from o v e r l y i n g r a d i o l a r i t e s ( S p a l l e t t a , et a i . , 1 9 8 2 ) w h i c h are n e v e r found associated with these deposits (Galli,1980).Sponge spiculae of the type found here flourish in shallow-water carbonate environments, such as the B i m i n i Lagoon (Hay, et a i . , 1 9 8 7 ) , and in o t h e r l a g o o n a l areas in the Bahamas. S p o n s e
279
s p i c u l a e are a b u n d a n t in m a r g i n a l environments (Chouns and E l k e r n s , 1 9 7 ~ ) , as well as in s a b k h a facies. C o n c e n t r a t i o n s of sponges may have taken p l a c e in a s h o r e l i n e e n v i r o n m e n t . The b i t u m e n and the c a r b o n a c e o u s m a t e r i a l p r o d u c e d in an a n o x i c lagoon by the decay of o r g a n i c m a t t e r leads to an i n c r e a s e in the c o n c e n t r a t i o n of the c a r b o n d i o x i d e w h i c h in turn lowers the pH, therefore facilitating the silica replacement of c a r b o n a t e s (Walker,1960) and the p r e c i p i t a t i o n a l o n g fissures. Silica is i n o r g a n i c a l l y p r e c i p i t a t i n g in the e p h e m e r a l lakes a s s o c i a t e d with the C o o r o n g L a g o o n in S. A u s t r a l i a (Peterson and Von Der B o r k , 1 9 6 5 ) . N e a r b y deposits to these silcretes consist of l o w - a n g l e l a m i n a t e d , d o l o m i t e layers a l t e r n a t i n g w i t h thin c m - t h i c k h o r i z o n s c o m p o s e d of s c a l e n o e d r i c c a l c i t e (B ). Some low-angle l a m i n a t e d sets are c o m p o s e d of f r a g m e n t s of s c a l e n o e d r i c c a l c i t e . O x y g e n - i s o t o p e data from c r y s t a l s of this type (Sch~nlaub,et ai.;1991) indicate a meteoric origin. D o l o m i t e is c o m m o n l y a s s o c i a t e d w i t h b e a c h d e p o s i t s b e c a u s e the area l a n d w a r d of the beach is a d i s c h a r g e zone for c o n t i n e n t a l g r o u n d w a t e r s . An actual e x a m p l e occurs in the C o o r o n g Lagoon, in south A u s t r a l i a . Algal tufas (C) c o n s i s t of an a l t e r n a t i o n of t u b u l a r and laminar bands; they are quite s i m i l a r to some components described from present-day terrestrial cyanobacterial stromatolites (Galli and S a r t i , 1 9 8 9 ) , T h e close association of bitumen, silcrete deposits, barite, fuorite, sphalerite, dolomite, b e a c h deposits, algal tufas and o r g a n i c m a t t e r p o i n t s to a d e p o s i t i o n in e p h e m e r a l , very s h a l l o w - w a t e r lagoons ranging from hypersaline to freshwater (cf. Galli,1983).Uplifts and b l o c k - f a u l t i n g may have p r o v i d e d the diastrophic background for the f o r m a t i o n of these marginal environments. m
The U p p e r D e v o n i a n - L o w e r C a r b o n i f e r o u s interval in the C a r n i c Alps is i n s t r u c t i v e b e c a u s e c o n t a i n s several features d e v e l o p e d t y p i c a l l y d u r i n g k r i k o g e n e t i c r e j u v e n a t i o n periodsl these are: l)onlap i n t r a s h e l f ramps in the p l a t f o r m ; 2 ) a n o x i o basinal facies; 3 ) d e p o s i t i o n of m e g a b r e c c i a s and s e i s m o t u r b i d i t e s ; A ) s t r i k e - s l i p t e c t o n i c s and f o r m a t i o n of d i v e r g e n t p a t t e r n s l 5 ) h i g h - s e i s m i o i t y ( S p a l l e t t a and V a i , 1 9 8 ~ ) i 6 ) p a l e o k a r s t s and relief inversions; 7 ) a c c e n t u a t i o n of s t o r m i n c i d e n c e on the p l a t f o r m ( G a l l i , 1 9 8 6 ) i 8 ) d r o w n i n g of the c a r b o n a t e p l a t f o r m at the Frasnian-Famennian boundary.
280
If one c o n s i d e r s g e o i d a l d e f o r m a t i o n as an e f f e c t of a g l o b a l c h a n g e in the shape of the g e o i d due to an i n c r e a s e in the rate of r o t a t i o n (Whyte,1977), c o n v e r g e n t w r e n c h i n g results to be a p h a s e of k r i k o g e n e t i c rejuvenation activity (Wezel,1988). The record of the punctuated, patohyly distributed geoidal d e f o r m a t i o n on the g l o b e , o r s t r i k e - s l i p t e c t o n i c s , d e p e n d s u p o n whether the deformed area is located within or outside a strike-slip megashear (cf. C a r e y , 1 9 8 8 ) w h i c h b e c o m e s a c t i v a t e d d u r i n g p h a s e s of g e o i d a l d e f o r m a t i o n (change from p r o l a t e to o b l a t e shape: W h y t e , 1 9 7 7 ) . The two case h i s t o r i e s summarized above, d o c u m e n t i n g r e l i e f i n v e r s i o n s in the V a l a n g i n i a n (Betic Cordillera) and Late D e v o n i a n - C a r b o n i f e r o u s (Carnie Alps) w e r e both localized within transcurrent megashears.
Relativistic
distribution
'event
of
horizons'
Introduction
The g e o l o g i c a l c o l u m n is p u n c t u a t e d by rare 'events', such as drownings of p l a t f o r m s , faunal extinctions,global short-term episodes of r e l a t i v e se-level change, and so on. S e v e r a l of these e v e n t s are not d i s t r i b u t e d at random, but c o n v e r s e l y are g r o u p e d w i t h i n s p e c i f i c time i n t e r v a l s ('event h o r i z o n s ' ) . The g r o w i n g i n t e r e s t in rare events, catastrophes and s u d d e n changes interrupting a presumed gradually evolving system fosters the views of the f o r e r u n n e r of c a t a s t r o p h i s m , Cuvier (1769-1832) who first reported from several stratigraphic successions sudden events represented by appearances and disappearances of fossil species ("Life ... has often been d i s t u r b e d on E a r t h by t e r r i b l e e v e n t s - c a l a m i t i e s ... w h i c h at the b e g i n n i n g , have p r o b a b l y m o v e d and o v e r t u r n e d to a g r e a t e r depth the entire outer crust of the globe" : cited from Raup ,1988: p.69). Since the b e g i n n i n g of E a r t h S c i e n c e s , catastrophists together w i t h t h e i r p r a e c u r s o r were r e g a r d e d as e c c e n t r i c p e o p l e b l i n d e d by t h e o l o g i c a l c r e e d who r e s o r t e d to i r r a t i o n a l , supernatural causes to e x p l a i n the e v o l u t i o n of n a t u r a l p r o c e s s e s . T h e r e a s o n of this v i e w regarding catastrophism has been explained by Raup (1988): "... In time, the u n i f o r m i t a r i a n v i e w of E a r t h h i s t o r y w o n d e c i s i v e l y o v e r the c a t a s t r o p h i s t view. It was a reflection of the a b h o r r e n c e of rare, unpredictable events, that is c o m m o n in m a n y fields of science. In any event, uniformitarianism (or g r a d u a l i s m , a s it is s o m e t i m e s called) has dominated geology a n d the education of ~eologists for the c e n t u r y a n d a half since the o r i g i n a l d e b a t e " . The p a r a d i g m of u n i f o r m i t a r i a n p r i n c i p l e s e s t a b l i s h e d by Lyell and H u t t o n c o n v e r s e l y s t a t e that " p r o c e s s e s that a c t e d in the past are in no way d i f f e r e n t from p r o c e s s e s a c t i n g today". The transformation of natural processes is thought to be a c u m u l a t i v e e f f e c t of small, t r i v i a l c h a n g e s , since the r e m o t e s t past. This concept is c r y s t a l l i z e d in the statement: "The p r e s e n t is the key to the past". A l s o the a c t u a l d e g r e e ,rate
283
a n d i n t e n s i t y of p r o c e s s e s a r e c o n s i d e r e d to be the s a m e as in the d i s t a n t p a s t . Stratigraphic a n a l y s i s h a s not e s c a p e d the application of the uniformitarian paradigm. The principles of Facies Models in sedimentology developed by W a l t h e r (1893) states that "only those facies and facies-areas can be superimposed primarily w h i c h c a n be o b s e r v e d b e s i d e e a c h o t h e r at p r e s e n t t i m e " . M o d a l c y c l e s a r e the p r o d u c t of the a p p l i c a t i o n of W a l t h e r ' s Law; in m o s t c a s e s h o w e v e r t h e y a r e o n l y an d e a l i z a t i o n of the r e a l i t y because they show what the situation would have been in a s c e n a r i o of g r a d u a l e n v i r o n m e n t a l shifting. T h e r e a r e s o m e b a s i c p r o b l e m s w i t h the W a l t h e r ' s Law. A f i r s t problem is the r e l a t i o n between the present-day accumulation r a t e of s e d i m e n t s a n d the g e o l o g i c a l preservation potential of a given sediment thickness. Sedimentologists studying the actual sediments are more concerned with the modality of deposition than with the preservation potential. A paradox in studying the stratigraphic sections is that most of the geological t i m e is n o t r e c o r d e d , d u e to n o n - d e p o s i t i o n or/and e r o s i o n . T h i s is p a r t i c u l a r l y evident where fluctuations of the b a s e l e v e l (level b e l o w w h i c h d e p o s i t i o n takes place under any condition) are frequent. Beds usually represent a small time compared to t h a t represented by b e d d i n g planes.Viewed under this perspective,beds are 'events'. When not produced by diagenesis, bedding planes represent changes in the environment.This means that the W a l t h e r ' s law is a p p l i c a b l e correctly only to t h e sediments representing a small time i n t e r v a l s e p a r a t e d by d i s c o n t i o n u i t i e s . The Walther's Law works well only when sequences do n o t record major breaks in sedimentary processes, when facies boundaries are g r a d a t i o n a l . The application of s t r a t i g r a p h i c g r a d u a l i s m h a s r e s u l t e d in t h e definition of F o r m a t i o n s and Members -diachronous rock unitswhich result from gradual environmental shifts. In several i n s t a n c e s F o r m a t i o n s do n o t h a v e a g e n e t i c m e a n i n g : t h e y a r e an a r t i f a c t of s t r a t i g r a p h i c gradualism; they have added confusion to t h e complexity of g e o l o g i c a l processes by leading to a complicated t a n g l e of n a m e s a n d s u b d i v i s i o n s w h i c h is f a m i l i a r to e v e r y g e o l o g i s t s t a r t i n g the s t u d y of s o m e n e w area. Goodwin and Anderson (1985) c h o s e d t h e 'PAC' as a f u n d a m e n t a l u n i t of a n a l y s i s of e p i s o d i c p u n c t u a t e d sediment accumulation; their reults contrasted a n d led to d i f f e r e n t interpretations f r o m t h o s e f o u n d e d on a g r a d u a l i s t i c approach: w h e r e a s the u s e of F o r m a t i o n s a n d M e m b e r s led to a d i s o r d e r e d stratigraphy, the u s e of P A C led to a v e r y o r d e r e d , layer-cake of s t r a t i g r a p h i c units bounded by s y n c h r o n o u s surfaces. The same approach is u s e d in s e q u e n c e stratigraphy, where sequence boundaries are
284
synchronous surfaces global process.
of
basinwide
extent,produced
by
some
The statement "The Present is t h e k e y to the p a s t " n e e d s s o m e reconsideration. For example, ~ust to c i t e f e w s i t u a t i o n s , the ancient epicontinental areas were characterized by a d i f f e r e n t water circulation and morphology} actual continental platforms underwent in the Quaternary atypical tectonic and glacial morphological modifications. Shelf regions are covered by relict sediments forming migrating sandwaves (i.e. along the e a s t e r n c o a s t s of N o r t h A m e r i c a ) . S h e l f m a r g i n m o d e l s , as w e l l as the B a h a m i a n m o d e l m u s t be u s e d w i t h c a u t i o n , a s s t r e s s e d by the same carbonate sedimentologists working in the area. Paleozoic oceans had different geometries: they were undersaturated with respect to calcium carbonate. Genetic models for Mesozoic deep-water sediments advanced by W i n t e r e r and Bosellini (1975) for t h e A l p i n e - Mediterranean region can n o t be a p p l i e d for recent oceans because of d i f f e r e n t calcium carbonate concentrations. T h e i n t e n s i t y of g e o l o g i c a l p r o c e s s e s h a s a l s o v a r i e d w i t h time: in t h e d i s t a n t g e o l o g i c a l p a s t t h e r e was a prevalence of thalassocratic conditions whereas at present an epeirocratic r e g i m e is p r e d o m i n a t i n g (emergent areas are prevailing). Some classes of d e p o s i t s and processes are better developed in t h e p a s t t h a t in t h e p r e s e n t : for e x a m p l e , the l a c k of v e g e t a t i o n a l c o v e r in t h e d i s t a n t p a s t led to m u c h h i g h e r r a t e of m e c h a n i c a l deposition. Orogeneses also increased in rate and volcanic activity since the Precambrian.Plate t e c t o n i c s p r o b a b l y d i d n o t o p e r a t e in the P a l e o z o i c . In s h o r t , t h e p r e s e n t r e p r e s e n t s o n l y a v e r y s m a l l f r a c t i o n of e v o l u t i o n of g e o l o g i c a l p r o c e s s e s c o m p a r e d to t h e s p a n i n t e r v a l of t i m e r e p r e s e n t e d by the Phanerozoic. A blind application of uniformitarian principles may correspond in s o m e c a s e s to a fixist
attitude.
The increasing i n t e r e s t in r a r e e v e n t s in t h e last d e c a d e s led to t h e n e e d to a c c o m p l i s h a distinction between continuous and discontinuous processes. Recent analyses have shown that most of p r o c e s s e s considered initially as c o n t i n u o u s , s u c h as t h o s e listed in A g e r (1981):erosion of a meandering river, reef growth, subsidence, uplift,pelagic deposition, heat flow, seafloor spreading, magnetic f i e l d , c o s m i c rays, are p u n c t u a t e d by d i s c o n t i n u i t i e s . The distinction a l s o d e p e n d s u p o n the s c a l e of o b s e r v a t i o n . The solar radiation i n t e n s i t y at v a r i o u s
for example undergoes discontinuities in s c a l e s , r e l a t e d to c h a n g e s in the m a g n e t i c
285
field below the photosphere. These discontinuities have a bearing on the terrestrial climate and weather such as an intensification of h u r r i c a n e strength, changes in t h e E a r t h ' s s p i n rate, s h i f t of c l i m a t i c z o n e s , a n d so on. The deep sea drilling pro~ect results indicate synchronous variations in the s e d i m e n t a t i o n rate of p e l a g i c deposition, formerly considered as c o n t i n u o u s . V a r i a t i o n s are related at v a r i o u s t e m p o r a l s c a l e s to c o o l i n g e p i s o d e s . The rate of sea floor spreadin~ is also punctuated by discontinuities; Schwan (1980) o b s e r v e d a coincidence between such discontinuities and unconformities of o r o g e n i c phases in orogenic belts. Orogenic deformation at a f i r s t a p p r o x i m a t i o n is a c o n t i n u o u s p r o c e s s as a n o r o g e n i c b e l t r e c o r d s a m i g r a t i o n of t h e d e f o r m a t i o n towards the f o r e l a n d (Vai,1987). Detailed s t u d i e s c o n d u c t e d in s e v e r a l o r o g e n i c b e l t s by V a i (1987) h a v e s h o w n t h a t the d e f o r m a t i o n is c o n c e n t r a t e d within specific time intervals.According to Stille (192~) orogenic phases and unconformities are episodic and correspond to t e c t o n i c p h a s e s . Conversely, uniformitarian views assume that orogenic phases are continuous9 a natural consequence of this view is t h e difficulty of i n t e r p r e t i n g the c a u s e f o r m a j o r u n c o n f o r m i t i e s delimiting depositional sequences which are normally attributed to e u s t a t i c sea level changes or to an obscure,not clear reorganization p h a s e of p l a t e t e c t o n i c a c t i v i t y (Bally,1980). Unconformities are considered by uniformitarians as perturbations of an o t h e r w i s e g r a d u a l l y e v o l v i n g p r o c e s s .
There I) 2)
are
two ways
of
considering
events
local
(Raup,1988):
e v e n t s m a y o c c u r as s u d d e n h a p p e n i n g s , totally unrelated to a p r o c e s s ~ events may subtend a process operating before the onset of the e v e n t in w h i c h c a s e t h e y m a r k t h e o v e r c o m i n g of a threshold.
Based point
on t h i s c o n c e p t , R a u p p (1988) events, a n d t h r e s h o l d e v e n t s .
made
a
distinction
between
As n a t u r a l processes become better understood, more and more point events shift into the threshold event category. For example,the t h e o r y p r o p o s e d by A l v a r e z et al., (1980) a c c o r d i n g to w h i c h the d i n o s a u r extinction was caused by a collision between an asteroid and the Earth, formerly considered as a random event, is n o w being reconsidered, in the light of
286
discoveries of o t h e r i r i d i u m a n o m a l i e s associated with minor extinction periods (Lower Devonian~Middle Miocene;end of Cenomanian; Eocene-Oligocene boundary). As our k n o w l e d g e of p h e n o m e n a increases, the idea of r a n d o m n e s s tends to be replaced with cause-effect relationships, as pointed out by a mathematician of the beginning of the twentieth century: "randomness is a m e a s u r e of our i g n o r a n c e " (Poincar4,1910). Hurricanes are n o r m a l l y considered as r a n d o m events. If we c o n s i d e r some of the s e v e r a l maps of h u r r i c a n e tracks h i t t i n g F l o r i d a p e n i n s u l a , we can c o n c l u d e w i t h o u t the s l i g h t e s t doubt that the p o s s i b i l i t y of s o m e h u r r i c a n e h i t t i n g the east F l o r i d a is r e g u l a t e d by c h a n c e . C o n v e r s e l y , t h e f i n d i n g of a t h i c k e n i n g u p w a r d s e q u e n c e g e n e r a t e d by h u r r i c a n e s and w i n t e r s t o r m layers in the Holocene Florida Bay, and successively of various analogous or identical sequences of different ages and locations in Europe (Galli,1990~ Fig.ll,12) led me to r e c o n s i d e r on one s i d e the r a n d o m n e s s of h u r r i c a n e s as r a n d o m e v e n t s , a n d , o n the o t h e r side, the use of the t e r m event as a synonymous of r a n d o m n e s s . In o t h e r words, how is it p o s s i b l e that r a n d o m e v e n t s f o r m a t r e n d ? Likewise, the q u e s t i o n I a t t e m p t e d at f o r m u l a t i n g in this w o r k is the f o l l o w i n g : how is it p o s s i b l e that events that are spaced from e a c h o t h e r s e v e r a l m i l l i o n s years form a t e m p o r a l s e q u e n c e of e v e n t s r e g u l a t e d by a g e o m e t r i c a l proportion? In fact, an i m p o r t a n t point observable from an e x a m i n a t i o n of Fig. IA9 is the t r e n d of s u c c e s s i v e lag times b e t w e e n the time intervals of s h o r t - t e r m sea level falls ( i n t e r p r e t e d as p h a s e s of p e r i o d s of g e o i d a l d e f o r m a t i o n ) . Such d i s c o n t i n u i t i e s are not d i s t r i b u t e d at r a n d o m b e c a u s e e a c h lag time b e t w e e n two t e m p o r a l d i s c o n t i n u i t i e s is a p p r o x i m a t e l y the half of the p r e c e d i n g one. Is this p u r e c h a n c e or does it underline some h i d d e n p h y s i c a l or g e o m e t r i c a l law?
Relativistic
The
study
object
of
of
'events',however
investigation
concept
new
in
of even. ~
Earth
sciences,
is
an
old
in P h y s i c s .
Events w e r e i n i t i a l l y s t u d i e d by Cusano, L e o n a r d o da V i n c i and Pacioli during the R e n a i s s a n c e period in Italy, in the X I V c e n t u r y . L e o n a r d o da V i n c i in p a r t i c u l a r s t u d i e d the m o d a l i t i e s
287
of f o r m a t i o n of impulse waves. He o b s e r v e d that sinusoidal waves u n d e r c e r t a i n c o n d i t i o n s c h a n g e t h e i r c o n f i g u r a t i o n with their t r a n s f o r m a t i o n into impulse waves, The study of discontinuities and events was successively u n d e r t a k e n by R i e m a n n , Gauss and C a n t o r in the X I X century, in Germany. It forms the basis for the development of the r e l a t i v i t y t h e o r y of Einstein. R i e m a n n d e m o n s t r a t e d that u n d e r d e f i n e d c o n d i t i o n s of a m p l i t u d e and w a v e l e n g t h the wave c h a n g e s its c o n f i g u r a t i o n from a s i n u s o i d a l and forms a d i s c o n t i n u o u s front which represents a discontinuity. This transformation takes p l a c e t h r o u g h d i s c r e t e a m o u n t s of e n e r g y , o r i n f i n i t e s i m a l q u a n t a of action. The c o n c e p t of 'event' is one of the c e n t r a l c o n c e p t s of the r e l a t i v i t y theory. An 'event' is c o n s i d e r e d as the i n t e r s e c t i o n point of the four s p a c e - t e m p o r a l c o o r d i n a t e s . T h e g e n e r a l t h e o r y of the r e l a t i v i t y implies the h y p o t h e s i s that nature, s o m e t i m e s c a l l e d the 'complex domain', can be a n a l y z e d t h r o u g h events. The space, r a t h e r than an a b s o l u t e state, as a s s u m e d by the Newtonian physics, is d e t e r m i n e d by the event distribution w h i c h c o n s t i t u t e s a non r i g i d s y s t e m of r e f e r e n c e , equivalent to a g a u s s i a n , c u r v e d q u a d r i d i m e n s i o n a l s y s t e m of c o o r d i n a t e s . The s u b s t i t u t i o n of time and space w i t h the t i m e - s p a c e d o m a i n involves the r e p l a c e m e n t of the c o n c e p t of m a t t e r with the event or e v e n t - p a r t i c l e concept. The r e a l i t y of a p h e n o m e n o n t h e r e f o r e r e p r e s e n t s a series of events. A g r o u p of events may be linked to e a c h o t h e r by a d e t e r m i n e d law; t h e i r c l u s t e r i n g may r e p r e s e n t the a r r i v a l point of s e v e r a l g e o d e s i c s (the p a t h from one e v e n t point to a n o t h e r is d e t e r m i n e d by the least action principle: a body follows the p a t h that c o r r e s p o n d to the m i n i m u m action: m a t e r i a l points move a l o n g g e o d e s i c s ) . A c l u s t e r of events, linked to a g r a v i t y center, c l o s e to a c u r v a t u r e of the s p a c e - t i m e domain, may be r e l a t e d to o t h e r s i m i l a r p o i n t s in the c h o s e d s y s t e m of c o o r d i n a t e s , w h i c h are the loci of s i m i l a r events. All these e v e n t s form a process. Matter is a mathematical construction based on the event distribution. Before E i n s t e i n Math s u b s t i t u t e d the c o n c e p t of space w i t h that of s u m m a t i o n of i n s t a n t a n e o u s d i s t a n c e s b e t w e e n m a t e r i a l points. The U n i v e r s e results to h a v e a d i s c o n t i n u o u s , c o r p u s c u l a r s t r u c t u r e w h o s e g e o m e t r i c a l p r o p e r t y is d e t e r m i n e d by the discontinuous distribution of event-matter. Several events clustered in the same space-time horizon are termed event h o r i z o n s . What e m e r g e d f r o m the r e l a t i v i t y t h e o r y developing a geometrical representation discontinuities.
was the p o s s i b i l i t y of the d i s t r i b u t i o n
of of
288
Neg-entropy
G i v e n a p o i n t 'x' in a n a t u r a l s y s t e m , o r m o r e g e n e r a l l y in t h e Universe, characterized b y a s e r i e s of p r o c e s s e s Pl ,P2 ,P3 ,,, Pn, a n y p a r a m e t e r is d e f i n e d b y t h e f o l l o w i n g f u n c t i o n : x
= g
(PI,P2...Pn)
(1)
According to this equation, organic processes control the development and geometrical properties of i n o r g a n i c processes which represent discontinuities or ' e v e n t s ' Schr~dinger associated the term neB-entropy to the p r o c e s s of formation and growth of organic processes, such as those characterizing living organisms. Neg-entropy is the o p p o s i t e than entropy; it is a m e a s u r e of the i n c r e a s e in t h e l e v e l of organization of a g i v e n p r o c e s s . L i f e is in f a c t a s s o c i a t e d to m i n i m u m v a l u e s of e n t r o p y ; it is in a c o n s t a n t disequilibrium state which contradicts the second principle of t e r m o d y n a m i c s equilibrium. A m e a s u r e of t h e n e g h e n t r o p y of a s y s t e m m a y by a c c o m p l i s h e d on a geometrical basis~ a geometrical approach stresses the relationship b e t w e e n the i n c r e a s e in t h e l e v e l of o r g a n i z a t i o n of the complex domain and the resulting increase in the associated neg-entropy~ The Gala hypothesis by Lovelock (1979) which considers the Earth as a n o r g a n i c whole, is a l s o b a s e d on the n e g e n t r o p y concept9 this hypothesis assumes that all processes on the globe are regulated by Life through an omeostatic, autoregolatory principle capable of maintaining conditions suitable to Life. This hypothesis has met with the actual orientation of reductive approach which may
resistance, probably because of science towards an opposite, be s c h e m a t i z e d by the following
equation: Y where which
= f(xl,x2...xn)
Y is a p r o c e s s , f a f u n c t i o n correspond to a s e r i e s of
(2)
of a s e r i e s differential
of p a r a m e t e r s equations.
x
Inherent in the (2) is the tendency to explain organic processes as a complicated combination between inorganic processes. T h e r e d u c t i v e a p p r o a c h is d o m i n a n t to o v e r w e l m i n g in
289 the s c i e n c e , w h i c h is c o n c e n t r a t e d on of structures which are considered complex domain.
the as
study and description the reality of the
T h e (I) c o n v e r s e l y implies that structures or discontinuities are t h e p r o d u c t of a t r a n s f o r m a t i o n of a n e g - e n t r o p i c process, m a i n l y a p r o c e s s of o r g a n i c g r o w t h .
Generation
O f singularities
A c c o r d i n g to R i e m a n n (185A) t h e o b j e c t of p h y s i c a l m a t h e m a t i c s a n d g e o m e t r y is the s t u d y of the p r o c e s s of t r a n s f o r m a t i o n from n o r d e r s e r i e s to a h i g h e r n+l order series. The infinitesimal calculus developed by Leibniz is also based on the same p r i n c i p l e s of g e n e r a t i o n of n u m e r i c a l series. One
can
consider
a given
series;
1,2,3,5,5,6
...
and two higher-order series, c u b e of the f i r s t s e r i e s :
I, I, The are
differences between the following:
4, 9, 8,27, the
(3)
respectively
the
square
and
the
16, 25, 36... 6~,125... terms
of
a
series
of
a
given
order
1, 4, 9, 16, 2 5 , 3 6 , a 9 , 6 ~ , . . 3, 5, 7, 9, 11, 1 3 , 15 T h e last s e r i e s r e p r e s e n t s a p r o c e s s of former, original series. The differences c a n a l s o be o b t a i n e d :
3, 2, The derived derives from this
case
the
This
process
5, 2,
7, 2,
9, 2,
13, 2,
transformation of the d e r i v e d
of the series
15... 2...
series of d i f f e r e n c e s indicate that each term the p r e v i o u s o n e b y a d d i n g t h e s a m e q u a n t i t y (in value is
'2').
known
as
the
invariant
law
of
transformation.
290
The process of transformation can be reverted with the g e n e r a t i o n of a f o r m e r s e r i e s t h r o u g h i n t e g r a t i o n or s u c c e s s i v e summations. In k e e p i n g w i t h R i e m a n n ("The m e t r i c of a p r o c e s s implies the generation of singularities"),numbers originate from the c o u n t i n g of s i n g u l a r i t i e s . The interval b e t w e e n two s u c c e s s i v e terms of a series of differences is characterized by an infinitesimal i n c r e m e n t dx to the s y s t e m w h i c h becomes visible only t h r o u g h the f o r m a t i o n of a new s i n g u l a r i t y . A consequence of the above conceptual scheme is that a neg-entropic process of growth takes place only with the generation of singularities which correspond to q u a n t a of action, that i s , t h r o u g h d i s c o n t i n u o u s ~umps.
Hierarchy
of s i n g u l a r i t i e s
A neg-entropic p r o c e s s c o n s i s t s of a d i s c o n t i n u o u s growth of s i n g u l a r i t i e s w h i c h takes p l a c e at d i f f e r e n t levels, This can be s c h e m a t i z e d in the f o l l o w i n g way, by c o n s i d e r i n g a s y s t e m of series of first, second, t h i r d order. xl x2 x3 xA
I, 2, I, A, I, 8, 1,16,
3, A, 5, 6,... 9, 16, 25, 36... 27, 6 & , 1 2 5 , 2 1 6 . . . 81,256...
The h o r i z o n t a l rows b e l o n g to a c l a s s or o r d e r of s i n g u l a r i t y N c h a r a c t e r i z e d by a g e o m e t r i c a l e x p a n s i o n . V e r t i c a l c o l u m n s are e x p o n e n t i a l s e r i e s N+I c o r r e s p o n d i n g to an e x p o n e n t i a l growth. Each of the s e r i e s N+I grows more r a p i d l y than any o t h e r of the f o r m e r s e r i e s b e l o n g i n g to the c l a s s N. The s e r i e s N + 2 a l o n g the d i a g o n a l correspond to a f u n c t i o n w h i c h grows e v e n more r a p i d l y t h a n the s e r i e s of t r a n s f o r m a t i o n N and N+I. The s e r i e s of higher-level
transformation N,N+I,N+2... procesds M which in turn
may be d e f i n e d by a generates M+I,M+2...
processes. A c c o r d i n g to R i e m a n n the m u l t i p l e d o m a i n is s t r u c t u r e d in this way) for example, the s c a l e of length of p h y s i c a l processes f o l l o w s an e x p o n e n t i a l geometrical increase in the o r d e r of magnitude. G e o l o g i c a l p r o c e s s e s d i s p l a y such a h i e r a r c h i c a l o r g a n i z a t i o n . The s c h e m e of d y n a m i c s t r a t i s r a p h y d e v e l o p e d by A i g n e r (1985) is an e x a m p l e of h i e r a r c h i c a l organizatioD based on three levels
of
stratigraphic
sequences
(Fig.16~).
291
O,1
m
boo,. _ , o 2 Y .
1
,o2_
Fig.16A Hierarchical stratigraphical sequences
Gemetrical
The modality neghentropic process may
,o , v.
.....]
,o4
_
,o6 y .
. ........ 1
analysis of three levels of (after Aigner,1985,with permission).
distribution
of
singularities
of g r o w t h of a l i v i n g o r g a n i s m , o r more generally,a growth, is k n o w n as s i m p l e o m o t h e t i c ~rowth. The be v i s u a l i z e d by m e a n s of a simple geometrical
scheme, In a p e n t a g o n - the t y p i c a l s y m m e t r y of l i v i n g o r g a n i s m s an omothetic g r o w t h l e a d s to an i n c r e a s e in s i z e w i t h a c o n s t a n t proportion , through the development of pentagons of progressively b i g g e r size. T h e g e o m e t r i c a l construction, quite simple, is obtained by prolonging the two sides of the triangles of F i g . 1 6 5 , until a side B and a diagonal A+B are constructed. This
growth
must
satisfy
C=A+B; The
omothetic
D=B+C;
proportion
the
following
E=C+D
proportions:
... A : B : B : C : C : D . . .
is d e f i n e d
as
follows:
292
time
axis
N÷2
E
E
E
E
D
D
N
S
S
A
F i g . 1 6 5 - Right: o m o t h e t i c g r o w t h of the p e n t a g o n a c c o r d i n g to the o m o t h e t i c p r o p o r t i o n . Left: the l o g - s p i r a l winding around the cones produces circular sections whose geometrical relationships vary according to the o m o t h e t i c proportion.C) Projection of the l o g , s p i r a l on the base of the c o n e . U p o n a complete rotation the d i s t a n c e from the axis of the cone is halved.
A+B=B:(A+B) The omothetic proportion, also known as golden section by a n c i e n t G r e e k s , is a f u n d a m e n t a l c h a r a c t e r of living b e i n g s and o r g a n i c p r o c e s s e s , or even i n o r g a n i c p r o c e s s e s d i r e c t l y d e r i v e d from o r g a n i c processes. It o c c u r s in D N A cells, microscopic organisms, trees, animals, shells, and so on. The simplest scheme of the o m o t h e t i c g r o w t h of a p o p u l a t i o n is g i v e n by the Fibonacci series (I,I,2,3,5,8,11...) whose successive rates (I/192/2~2/3~3/595/8...) r a p i d l y c o n v e r g e t o w a r d s the v a l u e s of the o m o t h e t i c p r o p o r t i o n . L i v i n g b e i n g s d i f f e r from i n o r g a n i c ones by t h e i r m o d a l i t y of g r o w t h w h i c h is r e g u l a t e d by the o m o t h e t i c p r o p o r t i o n and growth. The c o n c e p t of spiral c o n i c a l a c t i o n d e v e l o p e d by Gauss at the beginning of the X I X century is u s e f u l in e x p l a i n i n g the generation of s i n g u l a r i t i e s as the result of a p r o ~ e c t i o n of the r e l a t i v i s t i c s p a c e - t i m e c o n t i n u u m onto the e u c l i d e a n s y s t e m of c o o r d i n a t e s . The geometrical construction of v i s u a l i z e d as a s e c t i o n of a spiral
Fig.165 (right) can w h e r e the w i n d i n g of
be the
293
geodesic (or log-spiral) around a conic volume determines circular sections whose changes follow the omothetic proportion. A neg-entropic process can be t h o g h t of as an o u t w a r d and s i d e w a r d e x p a n s i o n p r o d u c e d by a c i r c u l a t o r y and r o t a t i o n a l w i n d i n g of the l o g - s p i r a l a r o u n d the c o n i c a l volume. The rate of n e g - e n t r o p i c g r o w t h is e x p r e s s e d by the angle of the cone. Singularities are formed through a 180 ° r o t a t i o n a r o u n d the cone. The f o r m a t i o n of a s i n g u l a r i t y c o r r e s p o n d s to a p h a s e change, or metrics, in the s y s t e m (Fig.166),
TIME AXIS
F i ~ . 1 6 6 - Series of d i s c o n t i n u i t i e s or s i n g u l a r i t i e s h a r m o n i c a l l y in the spiral conical action.
ordered
What is p e r c e i v e d as structures on a euclidean system of reference (i,e, F i g , 1 6 6 : l e f t ) is the p r o j e c t i o n of a p r o c e s s of c o n t i n u o u s a c t i o n from a n o n - e u c l i d e a n s y s t e m of r e f e r e n c e (the s p a c e - t i m e gaussian coordinate s y s t e m by E i n s t e i n ) , T h i s process can be visualized by the Fig.167 where the discontinuities, projected on the R i e m a n n s p h e r e , i n d i v i d u a t e a great circle~ singularities are invariant points and are maintained in the s t e r e o g r a p h i c projection o n t o a p l a n e cut normal to the axis of the ellipse; o t h e r e l e m e n t s , such as the c a r t e s i a n i n f i n i t y d i s a p p e a r as they are not i n v a r i a n t p o i n t s . A similar representation of n e g - e n t r o p i c process in c o n f o r m i t y w i t h the p r i n c i p l e s of the g e n e r a l r e l a t i v i t y was p r o d u c e d by Weyl who conceptualized the expansion of the Universe as originating from a s w a r m of particles spreading out along g e o d e s i c s from a point source, It can be c o n c l u d e d that n e g - e n t r o p i c p r o c e s s e s s h a v e a typical m o r p h o l o g y of g r o w t h and f u n c t i o n s d e r i v e d from the p r o c e s s of e x p a n s i o n of an a u t o s i m i l a r spiral structure, congruent with the o m o t h e t i c p r o p o r t i o n . A n e g - e n t r o p i c a c t i o n c o r r e s p o n d s to
294
t-m-~ I I I
| ! !
I I
I
Fig.167 - Stereographic projection of h y p e r b o l i c singularities or discontinuities o n the R i e m a n n s p h e r e . O b s e r v e t h a t on the sphere the cartesian infinities disappear. Successive j u m p s to u p p e r l e v e l s in the s y s t e m s i n d i v i d u a t e in the s p h e r e g r e a t e r spheric volumes;the ratios between spheric volumes converge towards the omothetic proportion. a s p i r a l w h i c h p r o d u c e s a c o m p l e t e r o t a t i o n b e t w e e n a s e r i e s of circles progressively increasing in size. There is an exponential acceleration u p w a r d s a n d s i d e w a r d s as a f u n c t i o n of t h e a n g l e of r o t a t i o n around the c o n i c a l action. The winding p a t h is a l o g - s p i r a l which defines on e a c h r o t a t i o n circular sections whose geometrical relations are defined by the omothetic proportion. A plane cut normal to t h e axis of the cone contains the pro~ection of t h e c i r c u l a r s e c t i o n s w h i c h a p p e a r as a s e r i e s of concentrioal circles whose distances from each other are defined by the omothetic proportion. An example of s u c h g e o m e t r i c a l organization is s h o w n b y t h e Kepler's reconstruction of the S o l a r S y s t e m . In K e p l e r ' s system, the S o l a r S y s t e m is d i v i d e d into t w o m a i n r e g i o n s ( e x c e p t i n g P l u t o ) . T h e r e a r e i n n e r p l a n e t s , c o m p o s e d of heavier elements, d e v o i d s of r i n g s a n d w i t h a s m a l l n u m b e r of satellites, and the outer planets characterized by a b i g size, a gaseous composition a n d a h i g h e r n u m b e r of s a t e l l i t e s . The division b e t w e e n t h e t w o z o n e s is t h e a s t e r o i d belt, occupied
295
by I 0 0 , 0 0 0 small bodies w h i c h c o r r e s p o n d to a p h a s e change, to a d i s c o n t i n u i t y b e t w e e n the two s e r i e s of planets, The orbits of the p l a n e t s are o r d e r e d h a r m o n i c a l l y in the way i n d i c a t e d by Gauss and Riemann: it is p o s s i b l e to c o n s t r u c t two series of a o n a e n t r i c a l , s l i g h t l y o b l i q u e s e c t i o n s for the two classes of p l a n e t s w h i c h may be c o n s i d e r e d as the p r o ~ e c t i o n s from a cone of the p l a n e s c o n t a i n i n g the orbits, n o r m a l to the axis of the cones, in each case the Sun and the A s t e r o i d Belt. The p l a n e t s a p p e a r to be located a l o n e a spiral ( l o g - s p i r a l ) on the p o i n t s that correspond to successive rotations of 180 ° of the l o g - s p i r a l a l o n e the cone. The d i s t a n c e b e t w e e n the p l a n e t s on the l o g - s p i r a l is c o n g r u e n t with the o m o t h e t i c p r o p o r t i o n .
Biolo~ical
evolution
At p r e s e n t the old c o n c e p t of g r a d u a l i s t i c evolution is b e i n g r e p l a c e d by m o d e l s of p u n c t u a t e d e v o l u t i o n , A c c o r d i n g to Dutuit (1986) the e v o l u t i o n of Life is a s t e p w i s e p r o c e s s progressing through discontinuous p h a s e changes. The e v o l u t i o n of living organisms corresponds to a neg-entropio exponential growth p r o c e s s in r e s p o n s e to an i n c r e a s e in the g l o b a l e n e r g y b u d g e t of the U n i v e r s e , D u t u i t ( 1 9 8 6 ) went b a c k to the e m e r g e n c e of the first germs of Life, 3.5 to ~ b i l l i o n y e a r s ago, P h o t o s y n t h e t i c bacteria, c o m p o s e d of a p r i m i t i v e n u c l e o u s , a p p e a r e d about 2.5 to 2 b i l l i o n years ago, as is t e s t i f i e d by the o c c u r r e n c e of microbial organo-sedimentary structures (stromatolites). Afterwards, e u k a r y o t e s a p p e a r e d about 1 b i l l i o n y e a r ago, The Ediakara fauna in A u s t r a l i a records the first a p p e a r a n c e of m e t a z o a n s , a p p r o x i m a t e l y 750 m i l l i o n y e a r s ago. Dutuit (1986) a t t e m p t e d at q u a n t i f y i n g t h r o u g h phase changes the e v o l u t i o n of v e r t e b r a t e s : their e v o l u t i o n w o u l d have taken p l a c e t h r o u g h the a c q u i s i t i o n of n e w p l a n e s of o r g a n i z a t i o n . The first stage is r e p r e s e n t e d by a d v a n c e d fished a p p r o x i m a t e l y ~50 m.y. ago, B e t w e e n the first and s the s e c o n d s t a g e , 3 0 0 to 3~0 m,y. ago, there was the a c q u i s i t i o n of carrying members, with the a p p e a r a n c e of a m p h i b i a n s . The s u p p o r t and l o c o m o t i o n i n v o l v e d an increase in the e n e r g y e x p e n s e s by a factor equal to I0. The third level involved a more advance in the o r g a n i z a t i o n m a r k e d by the e v o l u t i o n of a d v a n c e d reptiles (200 m.y. ago) t o w a r d s the m a m m a l i a n d e v e l o p m e n t , and the t r a n s i t i o n to endothermy which involved a greater action upon the e n v i r o n m e n t , T h e f o l l o w i n s level c o r r e s p o n d s to the e v o l u t i o n of mammals (135 m.y, ago). Here again, the temporal p u n c t u a t i o n of the p h a s e changes by
296
P P M 0 E P K J
?
TR P
C
D S
.
/ ~
~
~
Fig.168 - T r e e of L i f e of v e r t e b r a t e s . The arrows indicating the a p p r o x i m a t e l o c a t i o n of the 'event h o r i z o n s ' of Fig. 149, suggest a relation with phase changes in the evolution of vertebrates. N e w s t e p s of t h e e v o l u t i o n take place close or ~ust in o o r r e s p o n d a n o e with the event horizons. Dutuit
(1986)
is c o n g r u e n t
with
the
omothetic
proportion.
T h e i n c r e a s e in s i z e of i n d i v i d u a l p h i l a (i.e. e q u i d s ) m a y a l s o be t a k e n as a m e a s u r e of t h e c h a n g e in m e t r i c s o f the u n i v e r s a l evolution: in this case the increase in the energy is compensated b y a n i n c r e a s e in the m a s s of l i v i n g o r g a n i s m s , as follows from the well known formula : E = M c ~ . In r e l a t i v i s t i c t e r m s , t h e i n c r e a s e in s i z e a n d / o r c o m p l e x i t y of t h e o r g a n i s m s means that new mass is c r e a t e d because new energy is m a d e available
to
the
system,
297
Event
horizons
The g e o l o g i c a l column is p u n c t u a t e d by s h o r t - t e r m phases of global geoidal deformation (some of w h i c h c o n s i d e r e d in the above chapters), as shown in Fig. I A 9 . T h e intervals between these s t r a t i g r a p h i c h o r i z o n s are c o n g r u e n t w i t h the o m o t h e t i c proportion. These time intervals may be t h o u g h t of as s i n g u l a r i t i e s or 'events' of a s p i r a l - t y p e n e g - e n t r o p i c g r o w t h (Fig.169). T h e r e are two series (Fig. I A g ) , s e p a r a t e d by a p h a s e change dated approximately 38 m.y. ago w h i c h was a p e r i o d of increase in tectonic deformation, global diastrophic events, acceleration of the E a r t h ' s flattening pulses and g l o b a l cooling (Wezel, 1988) .
time
YPRESIA~NETIAN ~:--....2:~/)/CENOMANJAN \ TURONIAN VALANGINIAN ~--~
// V UPPERLtAS
-
I Fig.169 - Log-spiral arrangement of J u r a s s i c - T e r t i a r y event h o r i z o n s of F i g . l ~ 9 . E v e n t h o r i z o n s are s p a c e d 180 ° from each o t h e r (el. F i g . l ) , a n d b e c o m e more c l o s e l y s p a c e d w i t h t i m e , d u e to the u p w a r d w i d e n i n g of the spiral s p a c e - t i m e domain. It is not s u r p r i s i n g to find that several, d i f f e r e n t types of events are c l u s t e r e d within these h o r i z o n s , such as i r i d i u m storm accentuations, earthquakes, anomalies, extinctions, d r o w n i n g s of p l a t f o r m s , g l o b a l uplifts, p h a s e s of increase in the e v o l u t i o n of organisms. T h e s e time i n t e r v a l s c o r r e s p o n d to 'event horizons'.They may correspond to krikogenetic r e j u v e n a t i o n p e r i o d s (see I n t r o d u c t i o n ) . Event horizons may be t h o u g h t of as the point sources of attraction of events which converge towards the event horizons. Each event may be c o n s i d e r e d as a p o i n t - c o m p o n e n t of a l o g - s p i r a l p r o c e s s of w i n d i n g a r o u n d the c o n e and s u b ~ e c t e d to near the 'event horizon'.In fact, the event a deflection horizons correspond to p o i n t s of c u r v a t u r e increase of the r e l a t i v i s t i c s p a c e - t i m e domain.
298
0
~ ~
3
O
0
~/ i
I
,
;
o
\1lip
~
o
~
w
lu
NO~SS~ ~ ' ~
0
0 i N.~ £1 0~" Fig.170 - Double a r o u n d the cone.
singularity
formed
by
the
log
spiral
action
The p r o ~ e c t i o n of the 'event horizons' onto the time spiral of Fig.l shows that they are c l u s t e r e d into two zones with a 180 ° s p a c i n g from e a c h other. The two zones may c o r r e s p o n d to k r i k o g e n e t i c r e j u v e n a t i o n and k r i k o g e n e t i c q u i e s c e n c e periods. The 180 ° s p a c i n g may be e x p l a i n e d by the c o n c e p t of d o u b l e discontinuity obtained by a p r o j e c t i o n of a conical spiral a c t i o n on a p l a n e n o r m a l to the axis of the cone (Fig.170). In this respect, the m o d a l sequence described in the a b o v e c h a p t e r s ( d e e p e n i n g - u p w a r d p a s s i n g to s h a l l o w i n g - u p w a r d cycles; t r a n s i t i o n s from o n l a p to o f f l a p g e o m e t r y , d i v e r g e n t - c o n v e r g e n t patterns~ more in g e n e r a l all situations ranging from the g e o t e c t o n i c cycle: F i s . 2 to 'PAC' cycles) may be thought of as double discontinuities produced by the p r o j e c t i o n s onto our euclidean s y s t e m of c o o r d i n a t e s of a c o n i c a l spiral action (Fig.171).
299
GEOLOGICAL
LOG-SPIRAL
COLUMN
A
Fig.171
-
singularity
Modal of
sequence a
spiral-type
seen
as
process,
a
double
discontinuity
or
References
ABBATE,E., BORTOLOTTI,V. and SAGRI,M.(1981) - 01istostromes in the 01igoeene Macigno Formation ( F l o r e n c e a r e a ) . 2 n d Reg. Eur. Meeting,Bologna,Excursion Guidebook:f63-203. nuovo genere fra i ACCORSI BENINI,C.(1979) - Lithioperna,un grandi lamellibranchi della facies a Lithiotis.Morfologia, tassonomia ed analisi morfofunzionale.Boll.Soc. P a l e o n t . ital., 18(2):221-257. ACCORSI B E N I N I , C. a n d BROGLIO L O R I G A , C. (1977) - L i t h i o t i s G~mbel,1871 a Cochlearites Reis,1903. Revisione morfologica e tassonomica.Boll.Soc. Ital.,16(1): 15-60. AGER,D.V,(1981) Halsted
AHR,W.M.(1973) shelf
-
Press,New
The
nature
York,122
-
The
of
carbonate
model.Trans.Gulf
the
stratigraphic
record.
p.
Coast
ramp:
an
alternative
Assoc.Geol.,23rd
to
Ann.Cony.:
the 221-
225. AIGNER,T. (1982) Calcareous trempestites:storm-dominated stratification in U p p e r M u s c h e l k a l k limestones (Middle Trias,SW Germany). In:G.Einsele and A.Seilacher (Eds.),Cyclic and Event Stratification,Springer-Verlag:180-198. AIGNER,T.(1985) Earth
-
Storm
depositional
Sciences. Springer-Verlag,174
systems.Lecture
ALVAREZ,L.W., ALVAREZ,W., ASAR0,F. and MICHEL,H.V. Extraterrestrial c a u s e f o r the C r e t a c e o u s - T e r t i a r y Science,208:
notes
on
P. (1980) extinction.
1095-1108.
ANDERSON,E.J. (1971) The interpretation of calcarenite paleoenvironments:the Coeymans Formation L o w e r D e v o n i a n of N e w York. S.E.P.M. Guidebook, Eastern Section, Temple University, Philadelphia,
67 p.
ARTHUR,M.A. and SCHLANGER,S.0. (1979) Cretaceous Anoxic Events' as causal factors in development of reservoired g i a n t oil f i e l d s . A . A . P . G . B u l l . , 6 3 : 8 7 0 - 8 8 5 . AUBOIN,J.,
BOSELLINI,A.
and
COUSINS,M.(1965)
- Sur
'Ocean reef-
la p a l 4 o g 4 o -
301
graphie de (1):147-158. AUBOIN,J. vol.,Casa
la
V4n4tie
au
Jurassique.Mem.geopal.Univ.
and BROUSSE,R.(1977) editrice ambrosiana,654
- Compendio p.
AZZAROLI,A. and CITA,M.B.(1967) - Geologia vol.,Cisalpino Goliardica, M i l a n , 3 5 3 p. BAIN,R.J. carbonate
and TEETER,J.W. (1975) d e p o s i t s on K e y L a r g o , F l o r i d a .
BALL,M.M. (1967) Bahamas. J.Sedim.
geologia,2nd
stratigrafica.
2nd
Previously undescribed Geology:f37-139.
- Carbonate sand bodies Petrol.,37:556-591.
BALLY,A.W. (1980) Basins and 'Dynamics of Plate Interiors', American Geophysical U n i o n : 5-20.
di
Ferrara,5
of
Florida
and
the
subsidence-a summary. In: Geodynamics Series, vol.l,
BARBUJANI,C.,BOSELLINI,A. and SARTI,M. (1986) Vigilio nel Monte Baldo (Giurassico,Prealpi Univ. F e r r a r a ( N U o v a s e r i e ) , I X ( 2 ) : l g - 4 7 .
- L'oolite Venete).
di S a n Annali
BEACH,D.K.(1982) Depositional and diagenetic history of Pliocene and Pleistocene carbonates of NW Great Bahama Bank;evolution of a c a r b o n a t e platform. PhD thesis, Univ. of M i a m i , 6 6 0 p. BEACH,D.K. and GINSBURG,R.N.(1981) Facies succession of Pliocene-Pleistocene carbonates,Northwestern G r e a t B a h a m a Bank. Amer. A s s o c . P e t r o l . Geol. B u l I . , 6 A / I O : 1 6 3 4 - 1 6 ~ 2 . BEAUDRY~D. and MOORE,G.F. (1985) Cenozoic Evolution of W e s t Sumatra Bull.,6?(5): 742-759. BEAUMONT,C. 65:291-329.
(1981)
-
Foreland
Basins.
Seismic Forearc
stratigraphy and Basin, A.A.P.G.
Geophys.Ji.R.Astr.
Soc.,
BEBOUT,D.G. and LOUCKS,R.G.(1974) - Stuart City trend,Lower Cretaceous,South Texas: Austin, Texas,Univ. of T e x a s of Econ. Geol. R e p o r t of I n v e s t i g a t i o n s , 7 8 , 8 0 p. BEMI~ELEN.R.W. van earth's evolution.
(1966) - On M e g a - U n d a t i o n s : a Tectonophysics,3(2) :83-127.
- Isognomon BENINI,C. and BROGLI0 LORIGA,C.(1974) v. I h e r i n g 1903 e Gervilleioperna Krumbek i923
new
model
for
(Mytiloperna)
fra
i
grossi
302
lamellibranchi della facies Naz. L i n c e i , 5 7 ( 4 ) : 233-245.
a
"Lithiotis"
BERG,O.R. (1982) - Seismic Detection and and Turbidite Sequences: their Application Subtle Trap. A.A.P.G.BulI.,66(?):1271-1288.
del
Veneto.Accad.
Evaluation of D e l t a and Exploration for
BERNOULLI,D. and JENKINS,H. (197~) - A l p i n e , M e d i t e r r a n e a n , a n d Central Atlantic Mesozoic facies in relation to the early e v o l u t i o n of the T e t h y s . S . E . P . M . S p . P u b l . , 1 9 : 1 2 9 - 1 6 0 . BERSEZI0.R. and FORNACIARI,M.(1987) - Cretaceous the L o m b a r d y Basins:stratigraphic outline between L e c c o a n d I s e o . M e m . Soc, Geol. I t . , A 0 : 1 8 7 - 1 9 7 .
sequences the L a k e s
in of
BERTI CAVICCHI,A,,BOSELLINI,A. and BROGLI0 LORIGA,C.(1971) Lithiotis problematica Gumbel o Calcari Calcari a "Lithiotis?". Mem. G e o p a l e o n t o l . Univ. F e r r a r a , 3 ( I / 3 ) : A I - 5 3 .
a
BICHSEL,M. and HARING,M.O.(1981) - Facies evolution of L a t e Cretaceous F l y s c h in L o m b a r d y (northern Italy),Eol.Geol.Helv., 7A(2):383-A20. BLENDINGER.W.(198h) - Late Ladinian strike-slip tectonics of the M a r m o l a d a - C o s t a b e l l a a r e a ( D o l o m i t e s ) . J b . Geol. B u n d e s a n s t . , 127:307-319. BLENDINGER,W.(1985) i g n e o u s a c t i v i t y of
- Middle Triassic strike-slip tectonics and the D o l o m i t e s (Southern Alps).Tectonophys.,
I~3:105-121. BLENDINGER,W.(1986) - Isolated stationary carbonate platforms: the Middle Triassic (Ladinian) of the Marmolada area, Dolomites, Italy. S e d i m e n t o l . , 3 3 ; 1 5 7 - 1 8 3 . BLENDINGER,W.,PARROW,A. of t h e M . C e r n e r a - P i z the U p p e r A n i s i a n a n d
and KEPPLER,F.(1982) - Paleogeography del C o r v o area (Dolomites/Italy) during Ladinian.Geol.Rom.,21:217-23A,
BONAGA,G.,CANTELLI,C.,DE NUZZO,S.,GALLI,G., MONTANARI,R. and VANUCCI,F.(1989) Cieli sedimentari nella Formazione del D~rrenstein nei dintorni di Cortina d'Ampezzo (Triassico, Dolomiti Orientali), Giorn. Geol.,ser3,51/l:33-A3. BOSELLINI,A. (Giurassico (3):
A~I-A6~.
(1972) - P a l e o e c o l o g i a dei c a l c a r i a "Lithiotis" inferiore),prealpi Venete. Riv,ital.Paleontol.,78
303
BOSELLINI,A.(1973) - Modello geodinamico e paleotettonico delle Alpi M e r i d i o n a l i d u r a n t e il G i u r a s s i c o - C r e t a c i c o . Sue p o s s i b i l i a p p l i c a z i o n i agli A p p e n n i n i . Accad. Naz. Lincei, Q u a d . , 1 8 3 : 1 6 3 205. BOSELLINI,A. (1984) - Progradation platforms:examples from the T r i a s s i c Italy. S e d i m e n t o l o g y , 3 1 : l - 2 4 . B0SELLINI,A.(1989) - Dynamics S.E.P.M. Speo, Publ.,44: 2-13.
of
geometries of carbonate of the D o l o m i t e s , n o r t h e r n
Tethyan
carbonate
platforms.
BOSELLINI,A. and B R O G L I O LORIGA,C, (1971) - I " C a l c a r i G r i g i " di R o t z o (Giurassico inferiore, Altopiano di A S i a g o ) e loro inquadramento nella paleogeografia e nella evoluzione tettono-sedimentaria d e l l e Prealpi Venete. Ann. Univ. Ferrara, n.s.,IX,5(1): 1-61. BOSELLINI,A. and F E R I O L I , G . L . ( 1 9 8 8 ) - Sequenze deposizionali e discordanze nel G a r g a n o M e r i d i o n a l e . Atti del 740 congresso Soc. Geol. I t a l , : A 4 9 - A 5 4 . BOSELLINI,A. and T r i a s s i c
and HSU,K.J.(1973) - Mediterranean paleogeography, Nature,224:144-146,
plate
tectonic
BOSELLINI,A.,MASETTI,D. and SARTI,M.(1981) The Vajont Limestone: an o o l i t i c deep sea fan, M i d d l e Jurassic Venetian Alps. 2nd R e g i o n a l M e e t i n g I A S , B o l o g n a (Excursion Guidebook): 308-342. BOSELLINI,A. and W I N T E R E R , E . L . ( 1 9 7 5 ) - Pelagic limestone and radiolarite of the Tethyan Mesozoic. A genetic model. Geology,3:279-282. B0SENCE,D. (1988) Florida. IAS 9th 26-28.
- Trends European
in s h a l l o w - w a t e r carbonate mounds, Regional Meeting,Leuven (Abstr.):
BOURROUILH-LE J A N and T A L A N D I E R , J . ( 1 9 8 5 ) - S4dimentation et fracturation de haute 4n4rgi4 en m i l i e u r 4 c i f a l : T s u n a m i s , o u r a g a n s et c y c l o n e s et leurs e f f e c t s sur la s 4 d i m e n t o l o g i e et la g 4 o m o r p h o l o g i e d ' u n atoll: M o t u et Hoa, & R a n g i r o a , T u a m o t u , P a c i f i q u e SE, Mar. G e o i . , 6 7 : 2 6 3 - 3 3 3 . BRANDNER,R.(1984) - Meeresspiegelschwankungen und T e k t o n i k der T r i a s s der N W - T e t h y s . Jb. G e o l , B u n d e s a n s t . , 1 2 6 : 4 3 5 - 4 7 5 . BRENCHLEY,P.J.
and
NEWALL,G.(1982)
-
Storm-influenced
in
inner
304
shelf sand lobes in the Caradoc (Ordovician) Shropshire,England. J.Sediment, Petrol.,52(4):1257-1269. BRETT,C.E.(1983) environment of the W e s t e r n N e w Y o r k and
of
Sedimentology, facies and depositional Rochester Shale (Silurian,Wenlokian) in Ontario. J,Sediment. Petrol.,S3;9~7-971.
BROADHEAD,R.F., KEPFERLE,R.C. and POTTER,P.E. (1982) Stratigraphic and Sedimentologic Controls of Gas in ShaleE x a m p l e from U p p e r D e v o n i a n in N o r t h e r n Ohio. A.A.P,G.BulI.~ 66(I);10-27. BROGLIO LORIGA,C. and NERI,C.(1976) - Aspetti paleobiologioi e p a l e o g e o g r a f i c i d e l l a f a c i e s a " L i t h i o t i s " (Giurese inf.). Riv, ital. P a l e o n t , , 8 2 ( A ) : 6 5 1 - 7 0 6 . BR00KS,H.K.(1968) The Plio-Pleistocene of Florida,with special reference to the strata outcropping in the Caloosahatche River. In: Perkins,R.D.(Ed.), Late Cenozoic Stratigraphy of s o u t h e r n Florida. Miami Geol.Soc.Annual Field Trip:3-A2. BROWN,L.F.,Jr. and F I S C H E R , W , L , ( 1 9 7 7 ) - Seismic-stratigraphio i n t e r p r e t a t i o n of D e p o s i t i o n a l Systems: E x a m p l e s from B r a z i l i a n Rift and P u l l - A p a r t B a s i n s , A , A . P . G . M e m o i r , 2 6 : 2 1 3 - 2 a 8 . BRYANT,W.R.,MEYERHOFF,A.A.,BROWN,K.N,,FURRER,M.A,,PYLE,T.E. and ANTOINE,J.W.(1969) - Escarpments, reef trends, and d i a p i r i c structures. A.A.P.G.BulI.,53: 2506-2542. BURTON,R.,KENDALL~C.G.St,C. and L E R C H E , I . ( 1 9 8 7 ) - Out of Depth: on the Impossibility of Fathoming Eustasy from S t r a t i g r a p h i c Record. E a r t h Sci. R e v i e w s , 2 ~ : 2 3 7 - 2 7 7 , CANTELLI,C,,MANZONI,M. and geologiche preliminari sui d a l l a g a l l e r i a del P a s s o di It.,
8A:27-36~
our the
VAI,G,B.(1965-1968) Ricerche terreni paleozoici attraversati M . C r o c e Carnico. Boll.Sot. Geol.
87:183-193.
CANTELLI,C., SPALLETTA,C., VAI,G.B. and V E N T U R I N I , C . (1982) Sommersione della piattaforma e rifting devono-dinantiano e namuriano nella geologiadel Passo di M , C r o c e Carnico, In: Castellarin,A. and Vai,G.B,(Ed.),"Guida alla Geologic del Sudalpino centro-orientale". G u i d e Reg, G e o I . S . G . I . : 2 9 3 - 3 0 3 . CARBONE,F. and S I R N A , G . ( 1 9 8 1 ) - Upper Cretaceous Reef M o d e l s from Rocca di Cave and Adjacent Areas in Latium,Central Italy. S . E . P . M . S p . P u b l . , 3 0 ; ~ 2 7 - A ~ 5 .
305
CASTELLARIN,A,(1972) Evoluzione paleotettonica e sinsedimentaria del limite tra p i a t t a f o r m a veneta e bacino l o m b a r d o a n o r d di R i v a del G a r d a , G i o r . G e o l . , 3 8 : 1 1 - 2 1 2 . CASTELLARIN,A.(1982) Lineamenti ancestrali sudalpini. In:Castellarin,A, and Vai,G.B.(Eds.),'Guida alla geologia del Sudalpino centro-orientale',Guide Geol.Reg. S.G.I.;41-55. CASTELLARIN,A., MORTEN,L. and BARGOSSI, G.M. (1976) Conglomerati di c o n o i d e sottomarina nel flysch insubrico Mal~ e Rumo (Trento), Boll.Soc.Geol.It.,95:513-525. CASTELLARIN,A, and SARTORI,R,(1973a) - Dessication a n d l e a c h i n g r u g s in t h e C a l o a r i G r i g i i n f r a l i a s s i c (S.Massenza and Loppio,Trento,Italy).Eclogae geol. (2): 339-3~3, CASTELLARIN,A. infraliassici 221-2~8,
and di
di
shrinkage tidal flat Helv., 66
SARTORI,R, (1973b) I ciclotemi S.Massenza (Trento). Gior. Geologia, 39:
CATALOV,G.A. (1983) - T r i a s s i c o n c o i d s (Bulgaria).In: T.M. P e r y t (Ed.), C o a t e d Berlin Heidelberg: 398-~08. CAUSARAS, C,R. (1987) system, Dade County, Resources Investigation
from central Balkanides Grains, Springer-Verlag
-
Geology of the surficial aquifer Florida lithologic!ogs.U.S.G.S.Water Report, 86-~126.
CHOI,D.R. and GINSBURG,R.N. (1982) - S i l i c i c l a s t i o foundations of Q u a t e r n a r y r e e f s in t h e s o u t h e r n m o s t Belize Lagoon, British Honduras. Geol.Soc,Amer,Bull,,93:l16-126, CHOI,D.R. and HOLMES,C.W.(1982) - Foundations of Quaternary R e e f s in s o u t h - c e n t r a l Belize Lagoon, Central America. A.A.P.G. Buli.,66(12):2663-2681. CHOWNS,T.M. and ELKERNS, J,E. (1974) - The origin of q u a r t z geodes and cauliflower cherts through the silioifioation of anhydrite nodules. J,Sediment.Petrol.,~(3) : 885-903. CISNE,J.L. (1987) carbonate platforms.
Earthquakes recorded Nature,323 :320-322.
stratiphically
on
CLARI,P. (1975) Caratteristiche sedimentologiche e paleontologiche di a l c u n e s e z i o n i dei C a l c a r i G r i g i d e l V e n e t o . Mem. I s t . G e o l . Univ. P a d o v a , 3 1 : 2-63.
306
COLACICCHI,R.(1987) - Sedimentation controlled by sea level changes Mem. Soc. G e o l . I t . , A 0 : 1 9 9 - 2 0 8 . COOKE,C.W. (19~5) - G e o l o g y Geol. Bull., 29 ;339 p,
of
on a c a r b o n a t e and tectonic
Florida.
COPPER P,(1986) Frasnian/Famennian c o l d - w a t e r oceans. G e o I , , I ~ : 8 3 5 - 8 3 9 ,
Florida
mass
p l a t f o r m as movements.
Geol,
Survey
extinction
and
CRAIGHEAD,F,C.Sr.(1969)V e g e t a t i o n and R e c e n t S e d i m e n t a t i o n in E v e r g l a d e s N a t i o n a l Park, F l o r i d a N a t u r a l i s t ( r e p r i n t e d paper). CREMONINI,G.,ELMI,C, and della carta geologica L a m i s , R o m a 1971.
SELLI,R. d'Italia.
CREVELL0,P,D, and S C H L A G E R and turbidites,Exuma 50:1121-1148.
(1971) - Note illustrative Fg.156 San Marco in
W.(1980) - C a r b o n a t e debris sheets Sound,Bahamas: J.Sedim. Petrol,,
CROS,P.(1974) - Evolution s~dimentologique et p a l 4 o s t r u c t u r a l e de quelques plate-formes carbonat4es biog4nes (Trias des Dolomites italiennes).Sciences Terre, 1 9 : 2 9 9 - 3 7 9 . DAVIES,G.R.(1970) Algal-laminated sediments, Gladstone Embayment,Shark Bay,Western Australia.Mem.Am.Ass.Pet. Geol., 13: 169-205, DAVIES,T.D.(1980) Peat formation in Florida Bay and its~ignificance in i n t e r p r e t i n g the recent vegetational and geological history of the B a y area.PhD Thesis Pennsylvania State
Univ. S t a t e
College,Pennsylvania,316
p.
DAVIS,R.A.,Jr.,FOX,W,T.,HAYES,M,O. & B00THROYD,J,C.(1972) C o m p a r i s o n of r i d g e - a n d - r u n n e l systems in tidal and n o n - t i d a l environments.J.Sediment, Petrol,,32:A13-A21. DE
JONG,K,A.
and
SCHOLTEN,R,(Eds.)
(1973)
-
Gravity
and
T e c t o n i c s . W i l e y , N e w Y o r k , 5 0 2 p. DE J O N G , K , A , ( 1 9 7 3 ) - Mountain building in the M e d i t e r r a n e a n region, In: K.A. de J o n g and R.Scholten (Eds.),Gravity and tectonics,Wiley,N.York,502 DESIO,A.(1973)
- Geologia
DE S M E T , M . E . M . ( 1 9 8 d ) zone and its role
P, dell'Italia.
UTET,1081
p,
Investigations of the C r e v i l l e n t e in the tectogenesis of the
Fault Betic
307
zone and its role in C o r d i l l e r a , s o u t h e r n Spain.
the Vrije
tectogenesis of Univ.,Amsterdam,17A
the p.
Betic
DIXON, O.A., NARBONNE, G.M. and JONES,B, (1981) - Event correlation in Upper Silurian rocks of Sommerset I s l a n d , C a n a d i a n Arctic. B u l l . A m , A s s o c , P e t r , Geoi.,65:303-311 DOGLIONI,C. and BOSELLINI,A.(198A) - Platform Break-downlap r e l a t i o n s h i p in p r o g r a d i n g c a r b o n a t e b u i l d u p s : a tool for the reconstruction of basin evolution, Boll.Soc.Geol, It.,I08:175-182. DROXLER,A.W. and SCHLAGER,W, i n t e r g l a c i a l s e d i m e n t a t i o n rates Bahamas. Geology, 13 ;799-802.
(1985) and t u r b i d i t e
DOTT,R.H.Jr, & BOURGEOIS,J,(1982) - Hummocky s i g n i f i c a n c e of its v a r i a b l e b e d d i n g s e q u e n c e s . Bull.,?3; 663-680. EBERLI,G.P. (1987) - C a r b o n a t e t u r b i d i t e rift-basins of the Jurassic Tethys Switzerland). Sedimentol.,3~: 363-388. EBERLI,G.P. and GINSBURG,R.N. c o a l e s c e n c e of C e n o z o i c c a r b o n a t e B a h a m a Bank. G e o l o g y , Y 5 ; 75-79,
Glacial frequency
versus in the
stratification: G e o l , S o c , Amer.
s e q h e n c e s d e p o s i t e d in Ocean (eastern Alps,
(1987) Segmentation and platforms,north-western Great
E N O S , P . ( 1 9 7 7 ) - H o l o c e n e s e d i m e n t a c c u m u l a t i o n s of the F l o r i d a shelf margin, In: P.Enos and R,D.Perkins, Quaternary sedimentation in south Florida. Geol.Soc.of Amer.Memoir., 1~7:1-130. ENOS,P. and P E R K i N S , R . D . (1977) island s t r a t i g r a p h y , Geol. Soc.
- E v o l u t i o n of F l o r i d a Am, B u l i , , 9 0 : 5 9 - 8 3 .
Bay
from
E R S K I N S , R , D . and V A I L , P , R , ( 1 9 8 8 ) - S e i s m i c s t r a t i g r a p h y of the Exmouth Plateau. In: A.W.BalIy (Ed.), Atlas of Seismic S t r a t i g r a p h y , A , A , P , G , S t u d i e s in G e o l o g y , 2 7 ( 2 ) : 163-173. EVANS, C.C. diagenesis in Petrol.,57(2):
and GINSBURG,R,N, (1987) the Late P l e i s t o c e n e Miami 311-318.
Fabric-selective Limestone, J.Sedim.
EXON,N.F. and WILC0X,J.B, (1978) Geology and Petroleum potential of Exmouth Plateau Area off Western Australia, A.A.P.G.BulI.,62 (I): ~ 0 - 7 2 .
308
EXON,N.F., V O N RAD,U. and V O N STACKELBERG,U. (1982) - The G e o l o g i c a l D e v e l o p m e n t of the P a s s i v e M a r g i n s of the E x m o u t h P l a t e a u off N o r t h w e s t A u s t r a l i a . Nar. G e o l , , 4 7 : 1 3 ! - 1 5 2 . FABIANI,R.and Illustr.Carta Padova.
TREVISAN,L. (1939) Foglio Geol.Tre Venezie, Uff,Idr.R.Mag.
FERIOLI,G.(1986-1987) Thesis, Univ. F e r r a r a , 1 3 3 FERRARI,A.and
Geologia
Gargano
Meridionale.
p.
VAI,G.B.(1973)
Rhynchonellid g e n u s
del
Schio.Note Acque:l-88,
- Revision of the Fammennian Giorn. Geol.,39: 163-200.
Plectorhynchella,
FISCHER,A.G.(1966) The Triassic. Kansas Geol.Surv.
Lofer Cyclothems Buli.,I09:I07-149.
of
the
alpine
FISCHER,A.G. (1981) - C l i m a t i c o s c i l l a t i o n s in the b i o s p h e r e . In:"M.H.Nitecki ted.), 'Biotic crises in ecological and e v o l u t i o n a r y t i m e ' . A c a d e m i c Press, N e w Y o r k : f 0 3 - 1 3 3 . FUGANTI,A.(196A) - S t r u t t u r e g e o p e t e nei c a l c a r i Trentino e del Veronese (Alpi Orientali), Roveretana Agiati, 4(6):5-9,Rovereto,Trento.
m e s o z o i c i del Atti Accad.
FUGANTI,A, and M0SNA,S.(1966) Studio stratigrafico sedimentologioo e micropaleontologico d e l l e facies g i u r a s s i c h e del T r e n t i n o o c c i d e n t a l e . Studi T r e n t i n i Sol. N a t . , S . A . , A 3 ( 1 ) : 25-105. FROST,S.H.(1977) Cenozoic properties for p a l e o e c o l o g i c a l A.A,P,G.
reef systems of Caribbean synthesis. Studies in G e o l o g y ,
(4):93-II0.
GAETANI,M.,FOIS,E.,JADOUL,F. and N I C O R A , A . ( 1 9 S I ) - Nature evolution of Middle TRiassic carbonate buildups in Dolomites(Italy). Mar,Geol.,44:25-57. GALLI,G. (1980) Ombladet e dintorni B o l o g n a , 1 9 7 p.
Rilevamento e stratigrafia della (Alpi C a r n i c h e o c c i d e n t a l i ) . T h e s i s ,
and the
Cima Univ.
GALLI,G.(1983) - Marine evaporites w i t h s p e c i a l r e f e r e n c e to their relationship with base metal deposits.Msc, Thesis, I m p e r i a l C o l l e g e of S c i . & T h e c h n o l o g y , University of L o n d o n , 187 p. GALLI,G.(198A)
-
Studio
sedimentologico
preliminare
dei
309
carbonati devoniani della occidentali). Boll.Soc.Geol.
Cima Ombladet ital.,103:3AI-3A7.
(Alpi
Carniche
GALLI,G. (198A) - Hercynian synsedimentary tectonics: analytical data.Mem. Scienze Geologiche,XXXVI:A53-A60,Padova.
new
GALLI,G. (1985a) - Depositional environments in the D e v o n i a n i m e s t o n e s u c c e s s i o n of the C i m a O m b l a d e t (Carnic A l p s , I t a l y ) . Facies,12 :97-112 GALLI,G. (1985b) (Alpi Carniche) m a r k o v i a n a ) . Atti 70-8A.
- Depositi litorali carbonatici devoniani (Applicazione dell'analisi della catena Soc,Ital.Sc.Nat. & M u s e o C i v i c o Milano, 126:
GALLI,G. (1985c) - E c o l o g y Cima 0mbladet carbonate Italy). Palaeogeography, A9:265-275.
and d i s p e r s i o n of the fauna of the succession (Devonian,Carnie Alps, palaeoclimatology, Palaeoecology,
GALLI,G.(1986) Facies shoreline system (northern
analysis of a Devonian carbonate Italy).Sed. Geoi.,46:91-II0.
GALLI,G.(1986) - A n a l i s i d e l l e facies c a r b o n a t i c h e e t e r r i g e n e della F o r m a z i o n e d c e l l ' A u e r n i g nel P e r m o - C a r b o n i f e r o P o n t e b b a n o nella Alpi Carniche Orientali.Atti Soc.ital.Sci.nat. Nuseo Civ. S t o r . n a t . M i l a n o , 1 2 7 ( l - 2 ) : 3 - 1 2 . GALLI,G.(1988) - S t r u t t u r a delle rampe di i n t r a p i a t t a f o r m a con esempi d a l l e Alpi M e r i d i o n a l i e d a l l a p i a t t a f o r m a d e l l a F l o r i d a (Applicazione di concerti di sismostratigrafia nella ricostruzione di geometric carbonatiche di mare basso).PhD Thesis,Univ.Bologna,13A p. GALLI,G. (1989a) Depositional mechanisms of storm sedimentation in the T r i a s s i c D ~ r r e n s t e i n Formation,Dolomites, Italy.Sed, Geoi.,61:81-93, GALLI,G.(1989b) - Storm shore s e q u e n c e ( s o u t h e r n S t u t t g a r t , H 10: 590-602.
sedimentation Italy). Neues
in
a Quaternary rocky J a h r b u c h Geol. Pal.
GALLI,G.(1989c) - Is H o l o c e n e s t o r m - g e n e r a t e d s t r a t i f i c a t i o n in F l o r i d a Bay a r e f l e c t i o n of solar s t o r m c y c l e s ? P a l e o g e o g r a p h y , Palaeoecology, Palaeoclimatology,76: 169-185. GALLI,G. (1990) - Origins of event beds "Caloari G r i g i " Formation, V e n e r t i a n Alps, M i j n b o u w , 67 :375-390.
in the Jurassic Italy.Geologie en
310
GALLI,G. (1991) Depositional Model (Florida P l a t e a u ) .
Mangrove-Generated of the P l e i s t o c e n e Fort Facies, 2 5 : 2 9 7 - 3 1 A ,
Structures and Thompson Formation
GALLI,G.,CANTELLI,C. and L A M B O R G H I N I , P . (1985) statistica di livelli ghiaiosi (torrente Riv. Ital. G e o t e e n i c a , 4 ( X I X ) ; 1 9 9 ) 2 0 7 ,
- Correlazione Idice,Bologna).
GALLI,G. and SARTI,C. (1989) - F r e s h w a t e r s t r e a m s t r o m a t o l i t e s (Holocene, V i l l a Ghigi, Bologna, I t a l y ) . R e v u e de P a l e o b i o l o g i e , 8(I):39-A9. G A L L O W A Y , W . E . (1989) - G e n e t i c s t r a t i g r a p h i c s e q u e n c e s in basin a n a l y s i s , I A r c h i t e c t u r e and g e n e s i s of f l o o d i n g - s u r f a c e b o u n d e d d e p o s i t i o n a l units, A . A , P . G . B u l I . , 7 3 : I 2 5 - 1 A 2 . G A U P P , R . , M O L L E R , N . R . and B O R S C H I N S K Y , R . ( 1 9 8 1 ) - Epicontinental clastio sediments of the northern Calcareous Alps (Cenomanian-Turonian): e x a m p l e s of s y n t e c t o n i c s e d i m e n t a t i o n , IAS 2nd Reg, E u r o p e a n M e e t i n g , B o l o g n a ( A b s t r . ) : 6 9 - 7 2 . GEYER,0.F,(1977) - Die " L i t h i o t i s - K a l k e " im B e r e i c h der u n t e r ~urassischen Tethys.N.Jb,Geol.Palaont.,Abh,,153(3); 30A-3A0, GINSBURG,R.N.(1956) E n v i r o n m e n t a l r e l a t i o n s h i p s of g r a i n size and constituent particles in some south Florida carbonate sediments: A . A . P . G . B u l I . , A O :2384- 2A27. GOHNER,D.(1980) -"Covel del'Angiolono"-ein mittelliassisches LIthiotis-Schlammbioherm auf der Hochebene yon Lavarone (Provinz T r e n t o , N o r d i t a l i e n ) . N . J b , P a l ~ o n t o l o g i e A b h . , 1 0 : 600619. GOHNER,D,(1981) - B e i t r a g e zur K e n n t n i s des S u d a l p i n e n Juras mit b e s o n d e r e r B e r ~ c k s i c h t i g u n g der u n t e r j u r a s s i s c h e n L i t h i o t i s Fazies. I,Stratigraphie, Microfazies und Pal~ontologie, U n i v e r s i t ~ t S t u t t g a r t , 163 p. G I L D H A M M E R , R . K . , D U N N , P . A . and H A R D I E , L . A . ( 1 9 9 0 ) - Depositional cycles, composite sea-level changes,cycle stacking patterns, and the h i e r a r c h y of s t r a t i g r a p h i c forcing: Examples from Alpine Triassic platform carbonates, Geol, Soc.Amer, Bull., 102: 535-562. GOODWIN,P.W.and ANDERSON,E.J.(1985) - Punctuated cycles: a general hypothesis of episodic a c c u m u l a t i o n . J, G e o I . ~ 9 3 : 5 1 5 - 5 3 3 .
aggradational stratigraphic
311
GOODWIN, P . W . , A N D E R S O N , E.J.G00DMAN,W.M. and SARAKA, L . J . ( 1 9 8 6 ) - Punctuated aggradational cycles: i m p l i c a t i o n s for s t r a t i g r aphic analysis, Paleoceanography,l(A):417-A29, G R O T Z I N G E R , P. (1986) - C y c l i c i t y and palaeoenvironmental dynamics, Rocknest platform, n o r t h w e s t e r n Canada. Geol.Soc. Amer, B u l i , , 7 7 : 1 2 0 8 - 1 2 3 1 . GUIDISH,T.M.,LERCHE,I.,KENDALL,C.G.St.C. and O ' B R I E N , J . J . ( 1 9 8 A ) Relationship b e t w e e n E u s t a t i c Sea level c h a n g e s and b a s e m e n t subsidence.A.A.P.G.Bull.,68;16A-177. -
GUTTERIDGE,P. (1987) - D i n a n t i a n s e d i m e n t a t i o n on the s t r u c t u r e of the D e r b y s h i r e D o m e . G e o l . J . , 2 2 : 25-AI,
basement
HALLAM, A. (1978) - E u s t a t i c cycles in the Paleogeography, Palaeoclimatology, Palaeoecology,
Jurassic. 23:1-32.
HALLAM, A. (1981) - A Jurassic. J. Geol. Soc.
for
HALLOCK, P. demise of 398.
and coral
revised sea-level London,138:735-TA3.
curve
early
SCHLAGER, W. (1986) - N u t r i e n t e x c e s s and the reefs and c a r b o n a t e p l a t f o r m s . P a l a i o s , l : 3 8 9 -
HAQ,B.U., H A R D E N B O L , J . and fluctuating s e a - l e v e l since 1167,
VAIL, P.R. (1987) - C h r o n o l o g y of the T r i a s s i c . Science, 235: 1156-
HARDING, T.P. and LOWELL,J.D.(1979) - Structural plate tectonic habitats, and h y d r o c a r b o n traps provinces. A.A.P.G.BulI.,63/7:I016-1058. HARRIS, P. M. Bahamian cold
the
(1979) shoal.
Facies anatomy Sedimenta,7:l-163.
and
styles,their in p e t r o l e u m
diagenesis
of
a
HAY,W.W., W I E D E N M A Y E R , F . and M A R S Z A L E K , D.S. (1970) Modern Organism Communities of the B i m i n i L a g o o n and t h e i r R e l a t i o n to the S e d i m e n t . A t h A n n u a l F i e l d T r i p of M i a m i Geol. Soe.: 1930. HEEZEN, B. C., M A T T H E W S , J . L . , C A T A L A N O , R . , N A T L A N D , J . , C O O G A N , A . , THARP, M. and RAWSON, M. (1973) - W e s t e r n Pacific gujots. In: Heezen,B.C.,MacGregor,I.D. and o t h e r s ( E d s . ) , I n i t i a l r e p o r t s of the DSDP, 20, W a s h i n g t o n DC, US G o v e r n m e n t P r i n t i n g 0 f f i c e : 6 5 3 723.
312
HELLAND-HANSEN,W,,KENDALL,C,G.St,C., L E R C H E , I . and NAKAYAMA,K, (1988) - A s i m u l a t i o n of c o n t i n e n t a l b a s i n m a r g i n s e d i m e n t a t i o n in r e s p o n s e to crustal movements,eustatic s e a l e v e l c h a n g e and sedimentation accumulmation rates. M a t h e m a t i c a l G e o i . , 2 0 : 7 7 7 802. HINE,A. (1977) - L i l y u B a n k , B a h a m a s : h i s t o r y of sand shoal. J . S e d i m e n t . P e t r o l , , ~ 7 : 1 5 5 4 - 1 5 8 1 .
an active
HOFFMEISTER,J.E. and M U L T E R , H . G . (1965) - G e o l o g y the F l o r i d a Keys. G . S . A B u l i . , 7 0 9 : 1 4 8 7 - 1 5 0 2 . ILLIES,J.H.(1981) 7S:249-266.
- Mechanism
of g r a b e n
and
oolite
Origin
of
formation.Tectonophys.,
J A C K S O N , P,C. (1984) - P a l e o g e o g r a p h y of the L o w e r C r e t a c e o u s group of Western Canada. In: M a s t e r s , J , A . ( E d . ) , E l m w o r t h - C a s e s t u d y of a Deep B a s i n Gas F i e l d . A . A . P . G . M e m o i r , 3 8 : 4 9 - 7 7 . JAMES,N.P. (1972) - H o l o c e n e (caliche) p r o f i l e s : c r i t e r i a Petrol.,~2/4:817-836, JANSA,L.F, (1981) the e a s t e r n N o r t h
and Pleistocene calcareous crust for s u b a e r i a l e x p o s u r e . J , S e d i m e n t .
- Mesozoic carbonate p l a t f o r m s and banks A m e r i c a n margin. M a r , G e o l . , A A : 9 7 - 1 1 8 ,
JENKINS, H.C. (1991) - Impact A n o x i c E v e n t s on the M e s o z o i c A.A.P.G.BulI.,75(6):I007-1017.
of C r e t a c e o u s Sea Carbonate Platform
of
Level Rise and of Y u g o s l a v i a .
J O H N S O N , D.P., CUFF,C. and RHODES, E. (1984) - H o l o c e n e reef s e q u e n c e s and g e o c h e m i s t r y , B r i t o m a r t R e e f , C e n t r a l Great B a r r i e r Reef,Australia. Sediment.,31:515-529. JOHNSON, eustatic
J.G., K L A P P E R , G , and SANDBERG, C,A. (1985) - D e v o n i a n f l u c t u a t i o n s in E u r o a m e r i c a . B u l l . g e o l . S o o . A m . , 9 6 : 5 6 7 -
587. KENDALL, relative
C.G.St,C, and S C H L A G E R , W. c h a n g e s in s e a - l e v e l , M a r i n e
(1981) - C a r b o n a t e s G e o l . , A A : 181-212,
and
KENDALL, C.G.St.C. and SKIPWITH, P . A . D , E . (1969) - H o l o c e n e shallow-water carbonate and evaporite sediments of K h o r al Baxam, A b u D h a b i , S o u t h w e s t P e r s i a n Gulf, A . A . P . G . B u l I . , 5 3 : 841869. KIDWELL,S.M. (1991) - The s t r a t i g r a p h y of shell In: A l l i s o n , A . and B r i g g s , D . E . G . (Eds.),'Topics Plenum
Press,N.York,9:211-290.
concentrations. in G e o b i o l o g y ' ,
313
KINGSTON,D,R., DISHROON,C.P. and WILLIAMS,P.A. (1983) Basin Classification.A.A.P,G.Bull.,67(12):2175-2193. KREBS,W, (1974) Depositional carbonate Europe, SEPM Spec.Publ,,~8:155-208.
complexes
- Global
of
central
KREBS,W, and WACHENDORF,H.(1973) - Proterozoic - Paleozoio and Orogenic E v o l u t i o n of C e n t r a l E u r o p e . Geol,Soc.Amer. Bull.,8A: 2611-2630. KREISA,R.D. (1981) - S t o r m - g e n e r a t e d sedimentary structures in subtidal marine facies with examples from Middle and Upper 0 r d o v i c i a n of s o u t h w e s t e r n Virginia.J.Sediment.Petrol.,Sl:08230848. K R U M B E I N , W.C. and Sedimentation. Freeman
S l o s s , L,L, (1963) - S t r a t i g r a p h y & Co. (iI E d , ) , 6 6 0 p,
and
KUMAR,N. and SANDERS,J.E, (1976) - C h a r a c t e r i s t i c s of the s h o r e face s t o r m d e p o s i t s : modern and ancient examples. J.Sediment. Petrol,,A6:1A5-162. LAPORTE,L.F. (1967) - C a r b o n a t e d e p o s i t i o n near mean sealevel and resultant facies mosaic:Manlius Formation (Lower Devonian) of N e w Y o r k S t a t e , A . A . P . G , B u l I , , S I : 7 3 - 1 0 1 , LECKIE,D.A. and WALKER,R.G, (1982) - S t o r m - a n d t i d e - d o m i n a t e d shorelines in C r e t a c e o u s M o o s e b a r - L o w e r Gates interval: Outcrop e q u i v a l e n t s of D e e p B a s i n g a s t r a p , w e s t e r n Canada:A.A.P,G.Bull. ,66:138-157. LEMOINE,M.M.,BOURBON,M. and TRICART (1978) - Le J u r a s s i q u e et le Cretac4e p[r4piemontains ~ l'est de Briancon (Alpes occidentales) et l'4volution de la marge europ4enne de la Tethys: donn4es nouvelles et consequences.Acad. Sci,Comptes Rendus,286(ser.D):1237-12h0. LEONARDI,P.(Ed.) Isaroo e Piave. LOVELOCK,J,E.
(1967) - le D o l o m i t i , G e o l o g i a dei Two voll,.Cons.Naz.Ricerche,Roma,1019
(1979)
LOWENSTAM,H.A. (1950) J.Geol.,58:430-487. LOWENSTAM,H.A.
(1963)
- Gala.
Oxford
- Niagaran
-
tra
Univ,Press;,Oxford,176
reefs
Biological
monti p.
of
the
problems
Great
Lakes
relating
p, area.
to
the
314
composition and diagenesis (Ed.),'The earth sciences', Chicago:f37-195.
of sediments. In: T.W.Donnelly University of Chicago Press,
MACINTYRE,I.G.,BURKE,R.B. and S T U C K E N R A T H , R . recorded Holocene reef section, Isla P e r e z Reef, M e x i c o . G e o l o g y , 5 : 7 4 9 - 7 5 4 . MACINTYRE,I.G. and Caribbean fringing 1054-1072. MCLAREN,D.J.(1970) ~4: 801-815.
GLYNN,P.W. reef,Galeta
-
Time,
life
(1976) - Evolution of modern Point,Panama.A.A.P.G.Bull.,60:
and
MARABINI,S. and VAI,G.B.(1985) m a c r o t e t t o n i c a d e l l a Vena del G e s s o It., 10h: 21-42. MARSAGLIA,K.M. P a l e o z o i c and 117-142.
(1977) - T h i c k e s t core h o l e , A l a c r a n
boundaries.
J.Paleontol.,
Analisi delle facies e in Romagna. B o l l . S o c . G e o l .
and K L E I N , G . D e . V . (1983) - The p a l e o g e o g r a p h y of Mesozoic storm depositional systems. J . G e o l . , 9 1 :
MARTIN ALGARRA,A. (1988) - Paleogeographic Pennibetic (Betic Cordillera,southeastern R e g . M e e t g . o f S e d . , L e u v e n (abstr.) :138-139.
evolution of Spain). 9th
M A R T I N I S , B . and PAVAN,G. (1967) - N o t e i l l u s t r a t i v e g e o l o g i c a d ' I t a l i a . F g . 1 5 6 , S a n M a r c o in Lamis.
della
the IAS
carta
MASSE,J.P. and B O R G O M A N O , J . (1987) - Un m o d 4 1 e de t r a n s i t i o n plate-forme - bassin carbonat4s control4 p a r des p h 4 n o m ~ n e s tectoniques:le Cr4tac4 du G a r g a n o (Italia m4ridionale). C.R. Acad. S c . P a r i s , 3 0 A ( 1 0 ) : 5 2 1 - 5 2 6 . MASSE,J.P. b u i l d u p s of
and PHILIP,J.(1981) Cretaceous France.SEPM Spec.Publ.,30:399-A26.
coral-rudist
MATTAVELLI,L. and P A V A N , G . (1965) - S t u d i o p e t r o g r a f i c o delle facies c a r b o n a t e del Gargano. Rend. S o e . M i n e r a l . I t a l . , X X I , P a v i a . MATTHEWS,R.K. Jersey,2nd
(1984)
ed.,489
-
Dynamic
Stratigraphy.Prentice-Hall,New
p.
MEISSNER,F.F. (1972) - C y c l i c s e d i m e n t a t i o n in M i d d l e P e r m i a n s t r a t a of the P e r m i a n basin,West T e x a s and N e w Mexico. In: J.C.ELam and S.Chuber (Eds.),"Cyclic sedimentation in the P e r m i a n B a s i n " , 2 n d e d . , W e s t Texas G e o l . S o c . M i d l a n d Texas: 203232.
315
MENARD,H.W. (196~) H i l l , N e w Y o r k , 2 7 1 p.
Marine
Geology
of
the
Pacificl
McGraw-
M I A L L , A . D . (1973) - M a r k o v C h a i n A n a l y s i s a p p l i e d to an a n c i e n t a l l u v i a l p l a i n succession. J . S e d i m e n t , P e t r o l . , 2 0 : 3 & 7 - 3 6 A . M I A L L , A , D . (198~) - E u s t a t i c Sea Level C h a n g e s I n t e r p r e t e d from Seismic Stratigraphy: A Critique of the Methodology with P a r t i c u l a r R e f e r e n c e to the N o r t h Sea J u r a s s i c R e c o r d . A . A . P . G . Buli.,70(2):131-137. MILLIMAN,J.D. (1978) Continental MarEin off I029-I0~8.
Morphology and Structure of Upper Southern Brazil.A.A.P.G,Bull,,62(6):
MINISTRY OF E C O N O M I C AFFAIRS,ADM. OF M I N E S (1986) D e v o n i a n Events around the 01d Red C o n t i n e n t , A n n , S o c . B e l E i q u e , Spec. vol, "Aachen c o n g r . 1 9 8 6 , A v r i l 1 9 8 6 , 1 0 9 .
-
Late G4ol.
MITCHUM,R,M, Jr.,VAIL,P.R, and S A N G R E E , J . B , (1977) - S e i s m i c Stratigraphy and Global Changes of Sea Level,Part 6: S t r a t i g r a p h i c I n t e r p r e t a t i o n of S e i s m i c R e f l e c t i o n P a t t e r n s in Depsoitional Sequenoes.A.A.P.G,Memoi,26:llY-133, MITTERER,R.M. Pleistocene epimerization 275-282.
(1975) - Age and d i a g e n e t i c temperatures of deposits of Florida based on isoleucine in M e r c e n a r i a . Earth and P l a n e t a r y S o l . L e t t e r s , 2 8 :
M O L E N A A R , C . M . (1983) Depositional Lower Tertiary Rocks,Northeastern 1066-1080.
r e l a t i o n s of C r e t a c e o u s and ALaska.A.A.P.G.BulI.,67(7):
MOUGENOT,D.,BOILLOT,G. and REHAULT,J.P. S h e l f b r e a k types on p a s s i v e c o n t i n e n t a l examples,SEPM Sp.Publ.,33:61-77.
(1983) - Prograding margins:some european
MOUNT,J.F. (1982) Storm-surge ebb origin of hummocky c r o s s - s t r a t i f i e d units of the A n d r e w s M o u n t a i n M e m b e r , C a m p i t o Formation (Lower Cambrian), White-Inyo Mountains, Eastern California. J.Sediment.Petrol.,52(3):09~l-0958. MORNER,N.A. 123-151.
(1976)
- Eustasy
and G e o i d changes.
MORNER,N.A. (1981) Revolution analysis.Geology,9:3aa-3a6.
in
J, of Geol.,8~:
Cretaceous
sea-level
316
MULLINS,H.T,,GARDULSKI,A.F. and H I N E , A . C . ( 1 9 8 6 ) - Catastrophic collapse of the West Florida carbonate platform margin. Geology,l~: 167-170. MULLINS,H.T. Beginning of 30-33,
and the
HINE,A.C. end for
MULTER,H.G,(Ed,) (1977) environments Florida Publ. C o . , I o w a , ~ 1 5 p.
(1989) - Scalloped carbonate platforms.
bank margin: Geology, 17:
- Field G u i d e to some c a r b o n a t e rock Keys and W e s t e r n B a h a m a s - K e n d a l l / H u n t
HUTTI,E, RICCl LUCCHI,F.R.,SEGURET,M and Z A N Z U C C H I , G . (198A) Seismoturbidites: a new group of resedimented deposits. Har. G e o l . , 5 5 : 1 0 3 - 1 1 6 . NEGRA,M,H.,RABET,A.M.,BISMUTH,H. and A B D A L L A H , H , (1987) Upper C r e o a t e o u s r u d i s t reef c o m p l e x e s and s h a l l o w m a r i n e c a r b o n a t e s in c e n t r a l T u n i s i a . IAS 8th R e g . M e e t g . o f Sed,,Tunis, Excursion Guidebook:AS-88. 0RI,G.G.,ROVERI,M. and VANNONI,F. (1986) - Plio-Pleistooene sedimentation in the Apenninic-Adriatio foredeep (central Adriatic Sea,Italy),Spec. Publs. I A S , 8 ; 1 8 3 - 1 9 8 . PARKER,G.G.,FERGUSON,G.E,,LOVE,S,K. and O T H E R S (1955) - Water resources of southeastern Florida w i t h special r e f e r e n c e to geology and ground water of the Miami area, U,S,G,S,Water Supply
Paper
1255,965
p.
PARKINSON,R,W,(1989) - Decelerating Holocene sea-level rise and its i n f l u e n c e on s o u t h w e s t Florida coastal evolution: a transgressive-regressive stratigraphy, J,Sedim. P e t r o l . , 59/6: 960-972, PARONA,C.F.(192A)
- Trattato
di geologia.
Vallardi
ed.
PATTARA,E. (1966-1967) - Rilevamento geologico della dorsale Est di M o n t e S a n . A n g e l o ( F o g g i a ) , T h e s i s , Univ. of B o l o g n a . PAVAN,C. and PIRINI,C. (1966) - Stratigrafia del 1 5 7 , M . S . A n g e l o . Boil. Serv, Geol. I t a l . , L X X X V I , R o m a .
a
Foglio
PERKINS,R,D.(1977) - Depositional framework of P l e i s t o c e n e Rocks in S o u t h Florida. In: P.Enos and R,D.Perkins (Eds.), Quaternary Sedimentation in South Florida,Geol.Assoc,Am. Memoir,l~7:131-198,
317
PERYT,T.M. Berlin.
(Ed.)
(1983)
-
Coated
Grains.
Springer-Verlag,
P E T E R S O N , M . N . A , and VON DER B O R K , C . C . ( 1 9 6 5 ) - M o d e r n chert carbonate-precipitating locality. S c i e n c e , l A g : J 5 0 1 - 1 5 0 3 .
in a
PISA,G.,MARINELLI,M. and V I E L , G . ( 1 9 8 0 ) - Infraraibl Group: a proposal (southern Calcareous Alps,Italy). Riv.ital.Paleont. S t r a t i g r . , 85/3/~: 983-I002. PLAYFORD,P.E.(1980) - D e v o n i a n "Great B a r r i e r Reef" Basin,Western Australia:A.A.P.G.Bull.,64:81A-8A0.
of
Canning
P L A Y F O R D , P.E., M A C L A R E N , D.J., 0RTH, C.J., GILMORE, J.S. and GOODFELLOW, W.D.(198A) I r i d i u m a n o m a l y in the U p p e r D e v o n i a n of the C a n n i n g B a s i n , W e s t e r n A u s t r a l i a . S c i e n c e , 2 2 6 : A 3 7 - 4 3 9 . P01NCARE',H.
(1913)
-Derni4res
pens4es,ch.2.
POSAMENTIER,H.W., JERVEY,M.T. and V A I L , P . R . c o n t r o l s on c l a s t i e d e p o s i t i o n . I . C o n c e p t u a l Spec. Publ.,A2: 109-124. P R A T T , B . P . and J A M E S , N . P . ( 1 9 8 6 ) - The Ordovician) of w e s t e r n N e w f o u n d l a n d : for carbonate sedimentation in Sedimentol.,33: 313-3~3.
(1988) - Eustatic framework. S.E,P.M.
St.George Group (Lower tidal fiat island model shallow epeiric seas.
PRAY,L.C.(1966) Hurricane Betsy (1965) and nearshore carbonate s e d i m e n t s of the F l o r i d a K e y s . G e o l . S o c . of A m e r i c a Spec. p a p e r I 0 1 : 1 6 8 - 1 6 9 . PREAT,A.(198&) - Etude l i t o s t r a t i g r a p h i q u e et s 4 d i m e n t o l o g i q u e du G i v 4 t i e n b e l g e (Bassin du D i n a n t ) . P h D T h e s i s , U L B ,Bruxelles, 466 p. PRINCIPI,G. and T R E V E S , B . (198A) - Ii s i s t e m a c o r s o - a p p e n n i n o come p r i s m a di a c c r e z i o n e . Riflessi sul p r o b l e m a g e n e r a l e del limite A l p i - A p p e n n i n o . Mem. Soc. G e o l . I t , , 2 8 : S A 9 - 5 7 6 . PURDY, E.G. (1974) - K a r s t - d e t e r m i n e d facies p a t t e r n in B r i t i s h H o n d u r a s : H o l o c e n e c a r b o n a t e s e d i m e n t a t i o n m o d e l , A . A . P . G . Bull., 58:825-855. RAUP,D.M. (1988) - C h a n g i n g views of n a t u r a l c a t a s t r o p h e , The Great Ideas T o d a y , E n c y c l o p a e d i a B r i t a n n i c a , I n c . , C h i c a g o : 5 ~ - 7 7 .
318
READ,J.F.(1985) A.A.P.G.BulI.,67:I-21,
Carbonate
platform
facies
models.
REY,J.,ANDRE0,B.,GARCIA-HERNANDEZ,M.,MARTIN-ALGARRA,A,and VERA, J.A. (1990) - The L i a s s i c "Lithiotis" facies n o r t h of V 4 1 e z Rubio (Subbetic zone).Rev,Soo.Geol.Espana,3(l-2): 199-212. RIDING,R. and WRIGHT,V.P.(1981) - Paleosols and tidal-flat, lagoon sequences on a Carboniferous carbonate shelf: sedimentary associations of triple disconformities.J.Sedim. Petrol., 51(A): 1 3 2 3 - 1 3 3 9 . RICCI L U C C H I , F , R . (1978) - Miocene paleogeography and basin analysis in the P e r i a d r i a t i c Apennines. In: C . S q u i r e s (Ed.), 'Geology of I t a l y ' , E a r t h Sci Soc, of L i b y a : f 2 9 - 1 6 2 . RIEMANN,B. (185A) zu G r u n d e liegen.
- Uber die H y p o t h e s e n , w e l c h e der In: ' G e s a m m e l t e m a t e m a t i s c h e Werke'
Geometrie (1876).
ROBERTS,D.G. and C A S T O N , V . N . D , ( 1 9 7 5 ) Petroleum potential of the deep A t l a n t i c O c e a n . 9 t h W o r l d p e t r o l e u m cong. P r o c . , V , I I . A p p l i e d Sci, P u b l i s h e r , L t d . : 2 8 1 - 2 8 9 . ROYDEN,L. and K A R N E R , G . D . ( 1 9 8 A ) - Flexure litosphere Apennine and Carpatian foredeep basins: evidence i n s u f f i c i e n t t o p o g r a p h i c load. A . A , P . G . B u l I . , 6 8 : 7 0 & - 7 1 2 .
beneath for an
RUPPEL, S.C. and WALKER,K.R. (1982) Sedimentology distinction of carbonate buildups: Middle 0rdovician, T e n n e s s e e . J.Sedim. P e t r o l . , 5 2 ( A ) : 1 0 5 5 - 1 0 7 1 .
and East
RYAN,W.B.F.and CITA,M.B,(1978) - The n a t u r e and distribution of M e s s i n i a n erosional surfaces - indicators of a several kilometer deep Mediterranean in the M i o c e n e , M a r i n e Geol,,27: 193-230, SANDBERG,P.A. (1983) - An o s c i l l a t i n g trend in P h a n e r o z o i c carbonate mineralogy. Nature,305:19-22,
non
skeletal
SARG,J,F,(1988) Special
-
Carbonate
sequence
stratigraphy.
S.E.P.M.
Publ.,A2:155-181.
SCATUR0,D.M., STROBEL,J.S., KENDALL,C,G.St.C, WENDTE,J.C., B I S W A S , G . , B E Z D E K , J . and C A N N O N , R . (1989) J u d y Creek: a case study for a t w o - d i m e n s i o n a l sediment deposition simulation, S.E.P.M.Special Publ.,A4:63-76. SCHLAGER,W, (1981) - The p a r a d o x of d r o w n e d platforms. Geol.Soc.Am.Bull.,92:197-211.
reefs
and
carbonate
319
SCHLAGER,W.(1989) Drowning unconformities in carbonate p l a t f o r m s . In: 'Controls on carbonate platform and basin d e v e l o p m e n t ' .SEPM Spec. P u b l . , A 4 : 1 5 - 2 5 . SCHLAGER,W.(1991) - Depositional important factors in s e q u e n c e 109-130. -
bias and e n v i r o n m e n t a l c h a n g e stratigraphy, Sod. Geol.,70:
SCHLAGER,W. and CAMBER,O. (1986) - Submarine drowning unconformities, and self-erosion escarpments. Geology,IA:762-765.
slope angles, of limestone
SCHLAGER,W. and PHILIP,J. (1990) Cretaceous platforms. In: R . N . G i n s b u r g and B e a u d o i n , B . ( E d s . ) , Rhythms. N A T O ASC S e r . , S 0 4 : 1 7 3 - 1 9 5 .
carbonate "Event and
SCHLANGER,S.O. JENKINS,H.C. and PREMOLI SILVA,I. (1981) V o l c a n i s m and v e r t i c a l t e c t o n i c s in the P a c i f i c B a s i n r e l a t e d to global Cretaceous Transgressions. Earth Planet. Sci, Lett.,52:435-AAg. SCHOLL,D.W,(1963) - Sedimentation in m o d e r n coastal southwestern Florida.A.A.P.G.Bull.,47:1581-1603.
swamps,
SCHOLL,D,W., CRAIGHEAD,F.C.Sr. and S T U I V E R , M . ( 1 9 6 9 ) submergenoe ourve revised: its relation to s e d i m e n t a t i o n rates. S c i e n c e , 1 6 S : 562-564.
Florida coastal
SCHONLAUB,H.,KLEIN,P.,MAGARITZ,M.,PANTITSCH,G. and S C H A R B E R T , G and S. (1991) - L o w e r C a r b o n i f e r o u s Paleokarst in the Carnic Alps ( A u s t r i a , I t a l y ) , Facies,Z5:91-118. SCHWAN~W. (1980) - G e o d y n a m i c peaks in A l p i n o t y p e orogeneses and c h a n g e s in o c e a n - f l o o r s p r e a d i n g d u r i n g Late J u r a s s i c - L a t e Tertiary time.A.A.P.G.Bull.,64:359-373. SCHWARZACHER,W.(1975) -Sedimentation s t r a t i g r a p h y . E l s e v i e r , 3 8 2 p.
models
and
quantitative
SCOFFIN,T,P. (1977) - Sea-level features on reefs in the n o r t h e r n p r o v i n c e of the Great B a r r i e r R e e f . P r o o . 3 r d . Int,Coral Reef S y m p . , M i a m i , F l a . :319-324. SEGURET,M,, LABAUEE,P. and MADARIAGA,R. (198A) seismicity in the P y r e n e e s from m e g a t u r b i d i t e s of P y r e n e a n B a s i n (Spain), N a r . G e o l . , 5 5 : l 1 7 - 1 3 1 ,
Eocene the south
320
SELLI,R. (1962) - Le Q u a t e r n a i r e J o n i e n de la P 4 n i n s u l a Italienne.
m a r i n du v e r s a n t A d r i a t i q u e Q u a t e r n a r i a , 6: 391-~13.
SELLI,R.(1967) The Pliocene - Pleistocenen Boundary in italian marine sectors and its r e l a t i o n s h i p to continental s t r a t i g r a p h y , Progr. in 0 c e a n o g r . , A : 6 7 - 8 6 . SINNI,E.L. and BORG011A/NO,J. (1989) - Le C r ~ t a c 4 s u p 4 r i e u r des Murges sud-orientales (Italie M4ridionale): stratigraphie et 4 v o l u t i o n des p a l 4 o e n v i r o n m e n t s . Riv. It. Paleont. Str., 95 (2): 95-136. SINNI-LUPERTO,E. and sur la s t r a t i g r a p h i e i n f e r i e u r du G a r g a n o Strat.,9:33-66.
MASSE, J.P. (1986) - D o n n 4 e s nouvelles des c a l c a i r e s de p l a t e f o r m e du C r 4 t a c 4 (Italie m 4 r i d i o n a l e ) , Riv. ital.Paleont.
SKABERNE,D~(1987) - Megaturbidites in the P a l e o g e n e F l y s c h in the r e g i o n of A n h o v o (W S l o v e n i a , Y u g o s l a v i a ) . Mem,Soc. Geol. It,, ~ 0 : 2 3 1 - 2 3 9 . SLOSS,L,L. (198~) Comparative anatomy of cratonic unconformities. In:J.S.Schlee(Ed.),'Interregional Unconformities and H y d r o c a r b o n A c c u m u l a t i o n ' . A , A . P . G . M e m . , 3 6 : 7 - 3 6 . SI~LE,D.(1973) - S i l c r e t e s and a s s o c i a t e d s i l i c a d i a g e n e s i s in s o u t h e r n A f r i c a and A u s t r a l i a . J . S e d i m , petrol.A3(~):i077-1089. SHITH,D.B.,HARW00D,G.M,,PATTISON,J. and P E T T I G R E W , T . H . ( 1 9 8 6 ) A revised nomenclature for the U p p e r P e r m i a n s t r a t a in e a s t e r n england. In: G . M . H a r w o o d & D,M.Smith (Eds.), The English Zechstein and r e l a t e d topics. Spec, Publ, Geol. Soc. London, 22: 9-17. SOI~h~IERVILLE,J.D.(1979) A cyclicity in the e a r l y B r i g a n t i a n (D2) l i m e s t o n e s east of C l w y d i a n R a n g e , N o r t h W a l e s and its use in c o r r e l a t i o n . Geol. J . , I ~ : 6 8 - 8 6 . S P A L L E T T A , C . (1982) - Concordanza stratigrafica tra radiolariti e flysch ercinioo nelle Alpi (Devoniano-Silesiano). Mem. Soc, G e o l . I t a l . , 2 ~ : l l - 2 1 , SPALLETTA,C. parabreccias
carbonati Carniche
and V A I , G . B . (198~) Upper DEvonian intraclast i n t e r p r e t e d as s e i s m i t e s , Mar. G e o l . , 5 5 : 1 3 3 - 1 A A .
SPALLETTA,C.,VAI,G.B. and VENTURINI,C.(1980) ercinico nella geologia dei Monti Paularo C a r n i c h e ) . Hem. Soc. Geol. Ital.,20; 2~3-265,
e
II Dimon
Flysch (Alpi
321
SPALLETTA,C.,VAI,G,B. and VENTURINI,C.(1982) Controllo ambientale e stratigrafico delle m i n e r a l i z z a z i o n i in calcari devono dinantiani delle Alpi Carniche, Mem. Soc,Geol. Ital.,22:101-110. SPALLETTA,Vai,G,B. and VENTURINI,C. (1982) La Catena Paleocarnica. In: A , C a s t e l l a r i n and G . B . V A I ( E d s , ) , " G u i d a alla geologia del sudalpino centro-orientale",Guide regionali SGI,Bologna Technoprint:281-292, STACKELBERG,VON U,,EX0N,N.F.,VON RAD,U.,QUILTY,P.,SHAFIK,S., EIESDORF,H.,SEIBERTZ,E. and V E E V E R S , J . J . (1980) - Geology of the Exmouth and Wallaby Plateaus off northwest Australia: s a m p l i n g of s i e i s m i c sequences. BMR J of A u s t r a l i a n G e o l o g y and Geophysics,5: 113-140. STAMP,L.D,(1922) - An o u t l i n e Geol. M a g a z i n e , 5 9 : 4 8 1 - 5 0 1 .
of the T e r t i a r y
geology
STANLEY,S.M. (1966) - P a l e o e c o l o g y and d i a g e n e s i s Limestone,Florida. A.A.P,G,BulI.,50(?):1927-19AT. STILLE,H. (192A) - Grundfragen Gebr, B o r n t . , B e r l i n , 4 4 3 p.
der
of
Vergleichenden
of Burma.
Key
largo
Tectonik.
SWIFT,D.J.P,,HUDELSON,P.M.,BRENNER,R,L. and T H O M P S O N , P . ( 1 9 8 7 ) heir construction in a foreland basin:storm beds,shelf s a n d b o d i e s , and s h e l f - s l o p e d e p o s i t i o n a l s e q u e n c e s in the U p p e r Cretaceous Mesaverde Group,Book Cliffs,Utah. Sediment.,3A: 423~57. THIERSTEIN,H.R, and B E R G E R , W . H . (1978) ocean history. Nature,276:A61-~66,
-
Injection
events
in
TOUIR,J. (1986) - Etude s t r a t i g r a p h i q u e et t e c t o n o - s 4 d i m e n t a i r e des s 4 q u e n c e s du C r 4 t a c 4 sup4rieur du Jebel M r h i l a (Tunisie C e n t r a l ) , Thesis, Fac. Sci, Tunis, E a r t h Sci D p t , : l - 1 6 3 . TUNIS,G. Mesozoico Gortania,
and VENTURINI,S, (1986) - Nuove osservazioni sul delle Valli del Natisone (Friuli Orientale), Atti Mus. Friuli St. N a t , : l T - 6 8 .
TUNIS,G. and V E N T U R I N I , S , (1987) - N e w d a t a and i n t e r p r e t a t i o n on the g e o l o g y of the s o u t h e r n J u l i a n P r e a l p s (Eastern Friuli). Mem. Soo. Geol. I t . , ~ 0 : 2 1 9 - 2 2 9 . VAI,G.B.(1963)
-
Ricerche
geologiche
nel
Gruppo
del
Monte
322
Coglians e nella Geoi.,30:137-198. VAI,G.B.(1976) alpi. Mem. Soc,
zona
di
Volaia
(Alpi
Carniche).Giorn.
- Stratigrafia e paleogeografia Geol. I t a l . , 1 3 ( 1 ) : 7-37.
ercinica
VAI,G.B.(1980) - Sedimentary environments of D e v o n i a n l i m e s t o n e s in the s o u t h e r n Alps. L e t h a i a , 1 3 : 7 9 - 8 1 .
delle
pelagic
VAI,G.B. (1987) - Migrazione complessa del sistema frontedeformativo - avanfossa - cercine periferico: il caso dell' A p p e n n i n o s e t t e n t r i o n a l e . Mem. Soc. G e o l . I t . , 3 8 : 9 5 - 1 0 5 . VAI,G.B. and CASTELLARIN,A. (1988) - Southalpine Plain Apennine Arcs. IN: Wezel,F.C. (Ed.), 'The Arcs',Elsevier Pub.l.:253-278. VAI,G.B. a n d C O C O Z Z A , T . (1986) of the Hercynian chain in 2(I):95-II~,
- Tentative schematic Italy. Bull.Soc.g4ol.
versus origin
Pc of
zonation France,
VAI,G.B. and RICCI L U C C H I , F . (1976) - The V e n a del G e s s o northern Apennines: growth and mechanical breakdown g y p s i f i e d algal crusts. Mem. S o c . G e o l . I t . , 1 6 : 2 1 7 - 2 4 9 .
in of
VAI,G.B. and RICCI L U C C H I , F . (1977) - A l g a e B e a r i n g and c l a s t i c gypsum in a ' c a n n i b a l i s t i c ' evaporite basin: a case h i s t o r y from the Messinian of northern Apennines. Sedimentology, 2A8:211-2AA. VAIL, P.R. (1987) Seismic stratigraphy interpretation p r o c e d u r e . I n : A . W . B a l I y (Ed.), A t l a s of seismic stratigraphy (vol.l),A.A.P.G.Studies in Geol., 27:1-10. VAIL,P.R. and HAQ,B.U. Science, 2 A I : 5 9 9 .
(1988)
-
Sea
level
history
-
reply.
VAIL,.R.,HARDENBOL,J.and TODD,R.G. (198~) Jurassic unconformities, chronostratigraphy,and sea-level changes from seismic stratigraphy and b i o s t r a t i g r a p h y . In: J.S.Schlee (Ed.),"Interregional unconformities and hydrocarbon accumulation", A.A.P.G.Memoir 36:129-IAA. VAIL,P.R.,MITCHUM,R.M.Jr.,TODD,R.G.,WIDMIER,J.M.,THOMPSON,S.III, S#~NGREE,J.R.,DUBB,J.N. and HALSLID,W.G. (1977) Seismic stratigraphy and g l o b a l changes in s e a - l e v e l . In: C.E.Payton (Ed.),Seismio StratigraphyApplications to Hydrocarbon Exploration,A.A.P.G.Memoir,26:A9-205.
323
VAIL,P.R, and TODD,R.G.(1981) Northern North Sea Jurassic unconformities, chronostratigraphy and sea-level changes from seismic stratigraphy, In: L,V. Illing & G.D. Hobson (Eds.),Proceedings of the P e t r o l e u m Geol. of t h e C o n t i n e n t a l S h e l f of N W E u r o p s C o n f , , m a r c h 4 - 6 , 1 9 8 0 , L o n d o n , H e y d o n and Sons Ltd.,London:216-235, VANOSSI,M. and GOSS0,G.(1985) - Introduzione alla Brianzonese Ligure. Mem,Soc.Geol,It,,26:A&l-A61.
geologia
del
VAN STEENWINKEL,M.(1988) - The sedimentary history of the Dinant platform during the Devonian-Carboniferous transition, PhD thesis,Katholieke Universiteit Leuven, Belgium,173 p. VAN STEENWINKEL,M. (1990) - Sequence stratigraphy from 'spot' outcrops - example from a carbonate-dominated setting:Devonian Carboniferous transition,Dinant synclinorium (Belgium). Sed. Geol.,69 (3/~):259-280. VENERANDI PIRRI,I,(1978) Le paragenesi Hg,Ni,As,fluorite, barite nel Devoniano della Rend. Soc. It. Min, P e t r , , 3 3 ( 2 ) ; 8 2 1 - 8 h A . VENZ0,G,A.(1963) La Formazione dei Valterragnolo - Trentino. Giorn. Geol.,31:
a Zn,Cu,Pb,Sb, Catena Carnica.
"Calcari 1-25.
Grigi"
in
VIEL,G. (1979) - Litostratigrafia ladinica: una revisione. Ricostruzione paleogeografica e paleostrutturale della area Dolomitico - Cadorina (Alpi M e r i d i o n a l i ) . Parte I. R i v . i t a l . Paleont, Strat,,85(1):85-126;(2):297-352, VON DER dolomite
BORCH,C,C. and JONES,J.B, (1976) - Spherular modern from Coorong area, South Australia. Sedim.,23:587-591.
YOUNG,K.(1977) - Middle Cretaceous rocks of Mexico and Texas. In: B e b o u t , D , G , and Loucks,R.G. (Ed,),"Cretaceous c a r b o n a t e s of Texas and Mexico;applications to s u b s u r f a c e exploration",Univ, of T e x a s B u r e a u of E c o n o m i c Geology R e p o r t of I n v e s t i g a t i o n s , 89:325-332, WALKDEN,G.M.(1982) - Field Guide to t h e Lower Carboniferous rocks of the south east margin of the Derbyshire Block, Wirksworth to G r a n g e m i l l . P u b l . Dep. Geol, a n d M i n e r a l . , U n i v . of Aberdeen, 3. WALKDEN,G.M. and GUTTERIDGE,P.(1987) - Field Excursion to t h e Derbyshire Carbonate platform. Publ.Dep.Geol. and Mineral. U n i v . of A b e r d e e n , 5,
324
WALKER,K.R. (1974) - C o m m u n i t y p a t t e r n s : M i d d l e 0 r d o v i c i a n of T e n n e s s e e . In: Z i e g l e r , A . M . , W a l k e r , A . M , , A n d e r s o n , E . J . , Kauffman, E.G., G i n s b u r g , R . N . and J a m e s , N . P . ( E d s . ) " P r i n c i p l e s of B e n t h i c Community analysis",Sedimenta I V , C o m p a r a t i v e Sed. L a b . , U n i v , of Miami:9.1-9.9, WALKER,R.G., DUKE,W.L. and LECKIE,D.A. (1983) Hummocky stratification, s i g n i f i c a n c e of its v a r i a b l e b e d d i n g sequences: discussion. Geol.Soc.Amer. Bull.,9~:12AS-1251. WALKER, T.R. (1960) Carbonate replacement of detrital c r y s ~ l l i n e s i l i c a t e m i n e r a l s as a s o u r c e of a u t h i g e n i c silica in s e d i m e n t a r y r o c k s . G e o l . S o c . Amer. B u l I . , 7 1 : I A S - 1 5 2 . WANLESS,H.R.,TYRRELL,K.H,,TEDESCO,L.P. and D R A V I S , J . J . ( 1 9 8 8 ) Tidal-flat sedimentation from hurricane Kate, Caicos p l a t f o r m , B r i t i s h West I n d i e s . J . S e d . P e t r o l . , 5 8 ( A ) : 72A-738. WEISS,M.P. tectonics,
(1969) 0ncolites paleoecology and central Utah.A.A.P.G.BulI.,53:II05-1120.
Laramide
WESLEY,A.(1956) - Contributions to the k n o w l e d g e of the Grey Limestones of the Veneto. Part I. A r e v i s i o n of the flora fossilis formationis oolitichaeof the Z i g n o . M e m . I s t . G e o l , M i n . Univ. P a d o v a ~ 1 9 : l - 6 9 . WENDT,J. and FURSICH,F.T. (1980) ~acies analysis and paleogeography of the C a s s i a n Formation, Triassic, southern Alps. Riv. I t . P a l e o n t . S t r a t i g r . , 8 5 : 1 0 0 3 - 1 0 2 8 . WEZEL,F.C.(198&) - The T y r r e n i a n Sea: a r i f t e d basin.Hem. Soc.Geol. It.,2A (1982):531-568.
krikogenic-swell
WEZEL,F,C.(1985) Facies anossiche ed e p i s o d i globali.Giorn. Geol.,A7(l-2),ser.3°;281-286. WEZEL,F.C.(1988) tectonism.
Earth
structural
patterns
and
rhythmic
Phanerozoic
history.
Tectonophysics,IA6:l-AS.
WHYTE,M.A.(1977) Nature,
-
geotettonici
267:
-
Turning
points
in
679-682,
WILCOX,R.E,,HARDING,T.P. and S E E L E Y , D . R . ( 1 9 7 3 ) tectonics.A.A.P.G.Bull.,578:74-96. WILLI~/~S,B.G.and HUBBARD,R.J.(198A) Seismic framework and depositional sequences in the Brazil. M a r i n e and Petrol. G e o l o g y , 1 : 9 0 - 1 0 A .
-
Basic
wrench
Stratigraphic Santos Basin,
325
WINTERER, E.L. and BOSELLINI,A. (1981) Subsidence and sedimentation on the Jurassic passive continental margin, southern Alps,Italy.A.A.P.G.Bull.,65: 39~-A21. WORZEL,J.L.,BRYANT,W, and OTHERS (1969) the D e e p S e a D r i l l i n g P r o ~ e c t . , 1 0 , W a s h i n g t o n P r i n t i n g O f f i c e , 7 A 8 p.
Initial reports of D.C.,US Government
WRIGHT,V.P., PLATT,N.H. and WIMBLEDON,W.A, (1988) - Biogenic laminar calcretes: evidence of c a l c i f i e d root-mat horizons in paleosols.J.Sedim,Petrol.,35:603-620.
