The Nature of the Stratigraphical Record

The Nature of the Stratigraphical Record Third Edition

DEREK V. AGER Emeritus Professor of Geology, U11iversity College of S1.n11sea, Unit1ersily of Wales, UK

JOHN WILEY & SONS C hiclw!-ill't' ·

Nt'\\

1 ork · Bri...,banl' · Toronto · Singapore

Copyright © 1973, 1981, 1993 by D. V. Ager First published in Great Britain 1973 by The Macmillan Press Ltd, and in the USA by Halsted Press, a Division of John Wiley & Sons, Inc. Second edition 1981. Third ed ition published ·1993 by john Wiley & Sons Ltd, Baffins Lane, Chichester, West Sussex P019 1UD, England All rights reserved. No part of this book may be reproduced by any means, or transmitted, or translated into a machine language without the written permission of the publisher.

Other Wiley Editorial Offices John Wiley & Sons, Inc., 605 Third Avenue, New York, NY 10158-0012, USA jacaranda Wiley Ltd, G .P.O. Box 859, Brisbane, Queensland 4001, Aush·alia John Wiley & Sons (Canada) Ltd, 22 Worcester Road, Rexdale, O ntario M9W 1L1, Canada John W iley & Sons (SEA) Pte Ltd, 37 Jalan Pemimpin #05-04, 131ock B, Un1on fndustrial Building, Singapore 2057

Library of Congress Cataloging-in-Publication Data Ager, D. V. (Derek Victor) The na ture of the stratigraphical record I Derek V. Ager. - 3rd ed. p. em. Includes bibliographical references and index. ISBN 0-47L-93808-4 (paper) 1. Geology, Stratigraphic. I. Title. QE651.A37 1993 551 .7-dc2.0 92-30173 CIP

British Librnry Cataloguing in Publication Data A catalogue record for this book is available from the British I ibrary

ISBN 0-47 1-93808-4 rypt'~Ct Ill II 11pt Palatino by f)obbtc Tvpc.,l'lling I td, 1,1 \'ln fermenting in my brain for years and I had to write them lown before 1 become completely intoxicated. 1n a sense, it is -t riltigraphy looked at by a non-stratigrapher. I have always used 1i11d taught stratigraphy rather than actually made it, but I can offer the excuse that the non-combatant usually has a clearer pkture of the battle than the soldiers actually engaged in the l1ghti ng. It seems to me that the conclusions contained in this book are inescapable, if one is not too involved in the minutiae l'' stratigraphical correlation actually to see them. No doubt I shall be criticised for some of my generalisations, bt~ l I am unrepentant. It is sad if some of my details are wrong lll over-simplified, but 1 am obstinate enough to maintain that tiH· general principles, in which I am chiefly interested, are right. I h.1ve tried, as far as possible, to use examples which I have '-t't'll for myself and which have impressed me. If the Chalk and tl11• Wenlock Limestone also occur in Ruritania, then I am dPiightcd to hear it, but I have not seen them there, so it has 11111 n·~Jslen•d in my simple mind. My motto in this connection as th.1t of Llw great )oachirn Barrande-'C'est ce que j'ai vu'. I tiT tlw s.tml' Tl'•ls<m, I h.wc not made great use of the literature. ln1 lhv most p.lrl llt.lVI.' onlv n•fp1 r('d to bookd a few of the errors, I h.1\ t' inlr(lduu •d lurtlw r .1nd lwllt•t t''•lmpll'!' that h .wP cnmc to

xu

Preface to the Second Edition

my attention in the meantime and I have expanded here and there on the basis of my own subsequent experience and further thoughts. I thank many friends and correspondents from all over the world who have commented on tl'le first edition. I have tried to include the points they have raised, where appropriate, but r have also tried to keep the book short and therefore, I hope, readable. Derek Ager Swansea, 1980

The basic law of stratigraphy is the Law of Supposition - from Geological Howlers, edited by W. D. I. Rolfe (1980)

Preface to the Third Edition

1

Matthew wrote A prophet is not without honom, save in his o'' n country . . . ' I sometimes think that it should read An l11'nour is not without profit, save in its own country ... ' There 1.., 'ery little financial gain, however, to be h.ad from writing .,c iL•n tific books, unless one writes very popular standard school ll•xts. This is not one of those, though one American reviewer d1d kindly say that it was a 'must'. Fortunately I can declare 111 •sd f oblivious of the market-place philosophy that now p•· rvades my home country. I write because I enjoy writing and I pt~rl i cu larly enjoyed writing this book. I wc:ts delighted therefore, after the British publishers had dcl'iarcd the second edition 'out of print', that the American p11bl ishers, John Wiley & Sons, immediately agreed to produce th 1s th ird edition. It has certainly been very popular west of the Atl.111 11c and brought me a number of invitations to preach my hl'l\'l iLtl l creed in the United States and Canada. Indeed, in view ut the literature that has been published since the appearance l lf I I H' fi rst edition, my heretical creed seems to have become the llllhm4oxv of sh·atigraphy. We now read repeatedly ofrare events .111d s torm deposits, episodic evolution and extra-terrestrial 1mp.1c ts. Catastro phism is back again. An American author was g •'•H·ruu s enoug h to say of this book that it 'has profoundly mllul'IKL'U modern c:;lratigraphic thinking'. The '-iC ending shows ll1t1l il w,ls .m Americn n, and I am sure that the Queen would say .t r ,lti~ r,l phk.ll ' il' it L'\l'r cilmc into her conversation, so I will retain tlw t i ll ~· " " rt ''" .., .tnd .md o;; ltuw which provided the 'brownstone' houses of much of old N t•w York (it\ If \\l' go to the lligh Atlas of Morocco, we (llld l' Vt~ ll r!OSl'l Sllnil,ll'it it'S, \\ 1th bclSIL Ill truSiOnS and extrUSiOnS \\ 11 hin tlw f,Jmili.u rl'd s.mdstorw. I ltt\\'t'\'t'l', \\'l\1'11 lllhlkt· llwst• u1mp.1nson.., across thl• i\tlantic, IL.lll ,tltllll'>llw.tr rtlV rt •o~dt•ro.., s .n· in}~ : ' pl.lh'll'llnniL-...' t )bviollslv

10

The Nature of the Stratigraphical Record

if we close up the ocean again, the resemblances would not be

so startling. Very well, but then let us go right down to the southwest corner of the United States and look at the Moenkopi and associated formations of Arizona. The glorious colours of the Painted Desert are produced by the same sort of red and green 'marls' as we Europeans have in our Keuper. The road cuttings along Highway 40 in Arizona show red and green marls and thin sandstones with layers of gypsum, all of which would be perfectly at home along the banks of the River Severn (Figure 1.7). Similar sediments with evaporites are seen in the cores of salt-domes below the Cupido Limestone mentioned above in north-east Mexico. What is more, a recent stamp from Argentina showed a red sandstone pinnacle in the depression of Ischigualasto (the Valley of the Moon) which a visiting Chinese immediately identified as Triassic. I have since seen red Upper Triassic mudstones near Daye in southern China.

THE COAL MEASURES Again continental drift may be held to account for the remarkable similarity of the Upper Carboniferous (Pennsylvanian) Coal

Figure 1. 7 Road-cutti11g in the Triassic Moenkopi Formation, Hixhway 40 near Holhrook, Arizona, USA (DVA)

The Persistence of Facies

11

Measures on both sides of what one of the airlines now likes to call the 'Atlantic River'. As a non-specialist, I found it quite easy, with my scanty knowledge of the plants of the British Coal Measures, to identify most of the diverse flora of the famous Mazon Creek locality in Tilinois. Perhaps if I had been more of an expert the differences would have been more apparent, but l'xperts always tend to obscure the obvious. Certainly there are differences, especially in the better development of marine sediments in the American Pennsylvanian, but these in a way have obscured the resemblances; for work in America has concentrated on the marine fossils, whereas in I urope we have usually been forced to fall back on the nonmarine faunas and floras. It is now known, however, that as with the plants, the non-marine bivalves of the American Mid-West .tre very like those that extend from Ireland to Russia. Whatever the vertical and lateral changes in the Coal Measures, \\estill have to account for a general facies development in Late Carboniferous times that extends in essentially the same form .111 the way from Texas to the Donetz coal basin, north of the l.lspian Sea in the USSR. This amounts to some 170° of J1,ngitude, and closing up the Atlantic by a mere 40° does not tt•.l lly help aJI that much in explaining this remarkable phe nomenon. One looks in vain for a similar geographical o;ituation at the present day. The nearest approach I can think ''' rs around the deltas of south-east Asia.

LOWER CARBONIFEROUS LIMESTONE In Britain, the great limestone development of Early Carboniferous

age used to be called the 'Mountain Limestone' bt·l,\Use it formed so much of our upland scenery. In the early do~ys of mapping in the United States, geologists (no doubt with .t Furope-oriented education) had no difficulties in tracing the t.ll nili.lr 'Coal Measures' and the 'Mountain Limestone' of western I mnp t• from the Appalachians right across the Mid-West. "llw ( .urien~ Napoleon' in the Boulonnais region of northern I r .Hll l' (lrgurc 1.8) looks t''adh like the ' Empire State quarry' m lndi.tn.t (Figun• 1.9) Both liSl' ururl.lting wires to cut s mooth (,,u•s intlw F.trl\' C.llblllllt"t•rpu s linw:-lnnP, and wlwn'as thl' first (~lississ ippian)

12

The Nature of the Stratigraphical Record

Figure 1.8 Lower Carboniferous limestone, Carriere Napoleo11, near Marq11ise (Pas de Calais), France (OVA)

was used to build the high monument to the Grande Armee that overlooks Boulogne (with Napoleon at the top firmly turning his back on England), the Indiana quarry produced the stone facings for the Empire State Building in New York. All the physiographical features of the Mid-Western Mississippian are familiar to the man from the English Pennines or the Mendips. The Mammoth Cave of Kentucky is nothing more than a rather larger Americanised version of Wookey Hole in Somerset or the Dan-yr-Ogof caves in South Wales. However, this is a case where the stratigraphical wood cannot be seen for the nomenclatural trees. Whereas the British, in their old-fashioned way, have usually stuck to the general term 'Carboniferous Limestone' to cover all the varied carbonate facies of this age, the Americans-for very good local reasons- have

Tlte Persistence of Facies

13

11sure 1.9 Mississippian limestone, Empire State Quarn;, nenr Bloomi11gton, Indiana, USA (DVA)

11lowed the proliferation of formation names to obscure the unity nl the whole. St' the Early Carboniferous was again a time of very widespread ',,,bonate deposition. Not only were limestones deposited in I mope as far south as Cantabria and right across the Mid-West, thl also went a lot further. Thus in Arizona, the Redwall I mwstone of this age forms the steepest cliff in the Grand l,lllyon (Figure 1.10), and the name refers to the red staining pf tlw rock from the overlying Permo-Triass ic red beds, just as Ill tlw Avon Gorge at Bristol, the topmost Carboniferou s I lllll'~tone is reddened by the overlying Permo-Triassic deposits. unil., rly, right up in the Canadian Rockies, the Mississippian J(undh.• Limestone forms an impressive escarpment, for example lbm•t• l he town of Banff in Alberta (Figure 1.11). [n Alaska, it 1 tl11• Lisburne l.imestonc, with very similar characters. \'\ {' ~~.111 .1lso trace the early Carboniferou s limestones in the ''PJ't'o;itc din•l'tton into Asi.1. Thus in Kashmir, there is a thick lmw~ tunl' of thi!-.. .1gc, wry like its British counterpart and with 1 .uni l.11 f.wn.tllist. 'l'lw pl'rsistencC' ol fossils wi ll be the subject nf the lll:\l c h.tplt'l , hut ,, c.llllton.Hy noll' should perhaps be IUildt:d hl'll', fn1 tiH• f,unili.uit y of tlw foo.;si l n,lllll's may mere!}

14

Tlte Nnfttre of tile Stratigraphical Record

Figure 1.10 Redwall Limestmre (MississiJIIIIan) fomwrg tire most olntious cliff in tire Gmnd Canyon, as seen fmm tile Powell Memorial, Arizona, USA (OVA)

reflect the fact that they were studied by British palaeontolo gists. I am told that it also occurs in Western Australia.

FRASN IAN REEFS Still climbing down the column, the next great limestone developme nt we meet is in the lower part of the Upper Devoruan. This is the Frasruan Stage and presents us with what is, perhaps, the most remarkable example of aU. This was the heyday of reefs built by rugose corals and stromatopo roids. In some areas they started earlier (in the Givetian); elsewhere they lasted on into the Famennian , but in the Frasnian Stc1ge reefs and reef linwstoncs (in their bro,1dest scnsL') were l''\pcriencing tlwir finest

The Persistence of Facies

15

I 'S"rt' 1.11 Rundle Limestone (Mississippiau), forming tile escarpment of lvlou111 Rundle, above Banff, Alberta, Ca11ada (OVA)

lhHII

This is true, in a humble way, in the so-called type area

1f tlw Devonian in south-west England. It is true in the classic

t•t•fo; o f Belgium, northern France and south-west Germany. It t I lit.' in the beautiful karst country of Moravia in central ( tel lwslovakia. It is also true in southern Morocco, in the \nw 1acan Mid-West and in the Canadian Rockies, where the '" L'rnous rocks of these reefs form the most important oil t' t•rvoirs and the chief source of wealth in the province of \lhl'rl ., (Figure 1.12). In \Vcstern Australia too, magnificent reefs of this age are It•\ eh 1ped, perhaps the best in the world, notably in the splendid '(tiu n" of the Windjana Gorge (Figure 1.13).

THE OLD RED SANDSTONE llw o tlwr grL'ill facies of the Devonian is the continental red

"H.Ic:; tmw dL'Vo as one goes down the stratigraphical column, if one leaves behind the spectacles of the specialist and looks about one with lhl wondering eyes of a child, one never ceases to be amazed .11 the diversity and yet the uniformity of it all. No doubt my rC' 1ders will have bigger and better examples of the persistence !II f.1cies which so fascinates me in this chapter, but I write as fM ,,., possible from my own experience. Someone will probably It'll me of the almost incredible persistence of the Karroo .mdstones of southern and eastern Africa, or the Nubian ,111dstone s across northern Africa into the M.iddle East, or the I >.1kota Sandstone in the American West. 1 shall be glad to have mv prej udices confirmed. lh •fore leaving this matter of persistence I want to mention a lt•w special cases of persistence on a finer scale.

SPECIAL CASES have so far considered a number of examples of persistent on a rather grand scale; but there are more detailed .1rnples of it which in their way are even more amazing. I hus the Englishman, familiar with his Rhaetian sediments at thl' top of the Trias, cannot but be astounded when he reads I II t' Rh aetian deposits of Thailand and finds them described hi l l k pyritous shales with Rhaetavicula contorta, resting on red ' " 1....1nd sandstones, with evaporites, just like those of the vc1 n cliffs. Certainly the Rhaetian I have seen in southern I liWJW, for example on the south side of the Pyrenees and along lu hores of Lake lseo in northern Italy, is incredibly like that r Urit.lin, even in the way the fossils are preserved. One of the most famous of all fossiliferous deposits is the 1ll'nhofen Lithographic Stone of Bavaria in southern Germany. lh1" fine-g rai ned limestone is only developed over a very small rt tt, 11sually tho ught o f as a lagoonal deposit behind sponge t•fo ulh "tdt• of llw Bl.ll k "'l'.l.

24

The Nature of the Stratigraphical Record

Ager, D. V. (1968). 'The Lateral Persistence of Carbonate Facies in Europe and Adjacent Areas, Rep. 1968 Nat. Conf. Earth Sci., Banff, Alberta, pp. 16-20. A duplicated report summarising the main points of this chapter. Ager, D. V. (1970). 'On Seeing the Most Rocks', Proc. Geol. Ass. (H. H. Read volume), Vol. 81, pp. 421-427. A light-hearted contribution to a Festscll rift drawing attention to some of the points made in this chapter. Ager, D. V. (1980). The Geologt; of Europe. McGraw-Hill, Maidenhead, 535 pp. In which I recklessly try to summarise the geology of our fascinating continent and draw attention to many of the examples of the persistence of facies discussed in this chapter. Andrichuk, }. M. (1958) . 'Stratigraphy and Facies Analysis of Upper Devonian Reefs in Leduc, Stettler and Redwater Areas, Alberta', Bull. Am. Ass. Pet. Geol., Vol. 42, pp. 1-93. Classic paper on the late Devonian reefs of western Canada. Curry, D., Gray, F., Hamilton, D. and Smith, A. J. (1967). 'Upper Chalk from the Sea Bed, South of Cork, Eire', Proc. Geol. Soc., Lo11don, No. 1640, pp. 134-136. A further westerly extension of Upper Cretaceous Chalk. Dehm, R. (1956). 'Zeitgebunden e Gesteine und Organische Entwicklung', Geol. R1mdschau, Vol. 45, pp. 52-56. A brief paper on the persistence of the late Precambrian iron ores and the late Jurassic lithographic limestones. Gupta, V. J. and Dension, R. H. (1966). 'Devonian Fishes from Kashmir, lndia', Nature, Lond., Vol. 211, pp. 177-178. On the Old Red Sandstone facies in Kashmir. Lecompte, M. (1958). 'Les Recifs Paleozoiques en Belgique', Geol. Rundscltnu, Vol. 47, pp. 384-401. It is difficult to select one from Lecompte's voluminous works on the Devonian reefs of Belgium, but this gives the general picture. Lowenstam, H. (1957). 'Niagaran Reefs in the Great Lakes Area', Geol. Soc. Amer., Vol. 67, pp. 215-248. One of a series of notable papers on these mid-Silurian reefs. McGugan, A. (1965). 'Occurrence and Persistence of Thin Shelf Deposits of Uniform Lithology', Bull. Geol. Soc. A mer., Vol. 76, pp. 125-130 and 615-616. On persistent units in the Canadian Permian. Nikolov, I. (1969). 'Le Cretace lnferieur en Bulgarie', Bull. Soc. Ceo/. France, VoL 11, pp. 56-68. Nikolov, I. (1971). 'Uber die Lithofazies der Bc1rremc-Ablagerungcn in Bulgaricn', N. Jl1. Geol, Pnlaiinl Abit , Vol 139, pp 161-lnB

The Persistence of Facies

25

Two accounts of the Urgonian and associated rocks at the other end of Europe, showing the lenticular nature of this 'reef' facies. l'layford, P. E. and Lowry, D. C. (1967). 'Devonian Reef Complexes of the Canning Basin, Western Australia', Bull. Geol. Surv. W. J1ustralia, Vol. 118. Definitive paper on these remarkable late Devonian Australian reefs . 'Picldnaes, N. (1967). 'The Palaeogeography of the Tethyan Region During the Ordovician', in C. G. Adams and D. V. Ager (eds) Aspects 'f Tethyan Biogeography, Systemics Ass. Publ., No. 7, pp. 45-57. I >iscusses the persistence of certain Ordovician facies. I "·ndall, A. F. (1968). 'Three Great Basins of Precambrian Banded Iron !·ormation Deposition: A Systematic Comparison', Bull. Geol. Soc. 1\mer., Vol. 79, pp. 1527-1544. A general comparison of the West Australian, South African and North American basins. I rueman, A. E. (1946). 'StTatigraphical Problems in the Coal Measures nf Europe and North America', Quart. J. Geo/. Soc., Land., Vol. 102, pp. 49-86. l.1ssic paper on the Late Carboniferous of the northern hemisphere. \. n '-ilraaten, L. M . J. U. (1971). 'Origin of Solnhofen Limestone', Geol. 11f11/7ouw, Vol. 50, pp. 3- 8 (1971). l'roposes offshore sediment traps rather than back-reef lagoons. \\ •• li.Ke, P. (1972). 'The Geology of the Palaeozoic Rocks of the l .mlabrian Cordillera, North Spain', Proc. Geol. Ass., Vol. 83, pp 57-73. A general account of this wonderful Palaeozoic area, drawing .lilt ntion to some of the persistent facies . \\ lh.h, P. T. (1965). 'Cretaceous Outliers in South-West Ireland and I ht•tr Implications for Cretaceous Palaeogeography', Proc. Geol. Soc., I 1 ul, Vol. 1629, pp. 8-10. l~l~ ords a remarkable occmrence of Late Cretaceous Chalk in south\\t•,t Ire land.

2

The Fleeting Fossil

We all know that species come and go with frightening rapidity (in fact Homo sapiens has already exceeded the life expectancy of most species). We also know that the fossil record is fragmentary in the extreme. Yet it is the common experience of most palaeontologists that, just as lithological facies are persistent around the world, so are the fossils which they contain. Theoretically, we might expect this to be so, since the same environment tends to support the same kind of organisms, but in fact the persistence of some fossils appears to go far beyond what we know at the present day. I have already written about the geographical distribution of fossils (especially Mesozoic brachiopods) at nauseating length, so it is not appropriate to do so again. But I cannot resist mentioning two or three examples which are very well documented and which I believe in personally (one gets very sceptical about other people's records in palaeontology). One example is the late Triassic brachiopod Halorella, which is large and distinctive and which has been recorded from every continent except Antarctica, in rocks dating from quite a small span of late Triassic time (Figure 2.la). It has no apparent direct ancestors or descendants, yet it turns up simultaneously in places as far apart as Indonesia, Siberia, Turkey, New Zealand and Nevada. What is more, these forms are not only the same genus, but also the same species, and the Nevadan specimens have even (very justifiably) been put in the sam e subspecies as a form in the Austrian Alps.

The Fleeting Fossil

27

A distant relation of Halorella, called Peregrinella, is even more tl'markable in early Cretaceous rocks (Figure 2.lb). It is best known from the presbytery garden at Chatillon-en-Diois in the I rcnch Alps, but has also been found in a single block in Poland, •l'> a single specimen in Czechoslovakia, in southern China, in ( .1lifornia and at not more than two or three other places in the \\llrld. Yet it is one of the most distinctive brachiopods in the \\ho le record and it has internal structures which make it clear th.1l none of the abundant brachiopods in the strata above or lt·ll>W could possibly be classified as even distant relations. Its n me means, in fact, 'little stranger', though it is by no means ~>na il for a brachiopod. In other words, we have fossils that just suddenly appear unund the world at one moment in geological history and \\hence, and whither flown again, who knows'? One can understand this, perhaps, in the fragmentary record of a rare 111d little-known group, but the Mesozoic brachiopods are now \ 1'\ thoroughly documented in every stage and the relations u these large and distinctive forms can hardly have been missed. I use Mesozoic brachiopod examples because they are the only ll11''> I can believe in wholeheartedly from my own work, but 1'' oh.1bly every specialist can produce his own examples. At the ltlwr end of the animal kingdom, I might cite that well-loved J11 11saur Iguanodon, now identified in Africa, Australia, Asia and ptltbergen, besides its best-known English and Belgian haunts. I \'Cil taking into consideration phyla or classes as a whole, one '>Lruck (at least I am struck) by the remarkable way in which J 1rt JCtdar groups of fossils seem to have been 'in fashion' for 1 ' ' hlie and then return to a comparatively minor role. Why was lhl• t .1m brian 'the Age of the Trilobites' as the popular science '"~..; Len us? We know that there were plenty of other animal roups around, but in that period the trilobites seem to have hunin.1tcd almost everywhere. Similarly, the brachiopods and lt,d..; in the early CaTboniferous, the bivalves in the early Jmassic nd tlw echinoids in the Miocene. I ~n m l•Limes wonder at the sheer multiplicity of the oyster tlfi'IWt'll arc w1tn there must have been on the earliest Jurassic l'•l tluor'> over whal is now Europe, and Lhe millions upon nulh(l JI~ ~1f lrt'tllun•s (\\ h,lll'Vl'r they were) that chewed their way thw ••r, h lw ,1-;~H mud to produ( l' the tr,Kl' fossil 7.oophycos.

~

':::/'J

I

HALORELLA

and

HALORELLOIDEA

w 0

fl.,

I~

~~·'\x •

R pecies into another over long periods of time. I have long w ticised the notion that evolution can be studied by chasing fossil ll\ s lers up a single cliff, even though that approach was first brilliantly expounded by my most distinguished predecessor at '-,wansea. One must clearly study the variation of a species th roughout its geographical range, at one moment in geological t11ne, before one can claim that it has changed into something I am now very much of the opinion that most evolution p roceeds by sudden short steps or qua~~ fa as brilliantly expressed an rl•cent years by Stephen Gould and Nils Eldredge, who uggested that new species arise, not in the main centre of its .11 ·estors, but in peripheral, somewhat isolated populations. As ( ,, uld expressed it: 'The history of evolution is not one of stately u nlnlding, but a story of homeostatic equilibria, rarely disturbed h\ .rpid events of speciation.' He therefore concluded that many .,, the awkward breaks in the fossil record are more real than 'f'f'.lrCnt. So we come to a somewhat catastrophic attitude to t'\'olution. It is also probable, of course, that the peripheral populations will encounter the environmental differences that " all select particular characters. I he greatest problems in the fossil record, however, are the udden extinctions. Examples such as the disappearance of the hrh lsaurs have been chewed over and over ad nauseam, with t \'t l } possible cause blamed, from meteoric impact to chronic ,unstrp.1tion. For any one ecological group, such as the dinosaurs, 11 is comparatively easy to find a possible cause. It is much lt•..tbook way, along the outcrop, is of thinning nvcr thn•t• .1\t' ' ' 1th I hit kcr

;,, ~·.

MEN DIP AXIS

DORSET BASIN

MORETON -IN-MARSH AXIS

GLOUCESTERSHIRE BASIN

(a)

sw.

Men.dip OX IS

Dorset

(b)

MIDLAND BASIN

Moreton- In-Marsh axis

Vole of Gloucest er

N.E.

MARKET WEIGHTON AXIS

YORKSHIR E BASIN

Market We1ghton

N.E.

C1X.IS

Le1cestersh1re

Yorkshire Basin

figure 3.5 Contrasted t>ersions of the mriation 111 thickness of the lowennost jurassiC deposits 111 England: mriation along the outcrop showmg 'axes' and inten1ening 'basins'; (11) the same variation expressed (a) idealtsed text-book typt• in actual total thicknesses

"'"

\0

The Nature of the Stratigraphical Record

50 S

N CH ARM OUTH

RADSTOCK

dovoei

lb
oovoe1

~- ~

.

0

--

Jomesonl

.-

. ..

rorlc:oslclum

"'"'z N

all

o t hers

oxynolum Vl IJJ

oblusum

z. 0

turner1

N

. -- - -

..

-

semicosto tum

-

~-- -- ~ - -

buckl ondl

angulalum / I I OSICUS

pionorbiS

"' "'

"' "'

"'

32km

Figure 3.6 A ctual variation within constituent zones between the Dorset coast and the Mendip 'axis'

basins of sedimentation in between (Figure 3.5a). If we put in actual thicknesses, the ' axes' are not so obvious, but they are still there (Figure 3.5b). However, if we look at just one part of that story in detail, we find complications. Thus if we trace the zones of the Lower Lias (as it is called) from the Dorset 'basin' to the Mendip 'axis', we find that 11 of the 12 zones thin as they ought (Figure 3.6) with no signs of any breaks in the succession, but the twelfth actually thickens markedly! Such misbehaviour of strata in their most classic sections leads me to have serious doubts (in fact, positive hatred) of the concept of the 'stratotype' so much favoured by many workers on the European continent. l11is idea of type section for a particular stratigraphical division will be discussed in a later ch apte r; all J must say here is that no type section know n to me can poss ibly

More Gaps than Record

51

' '

I igure 3. 7 Stratigrapl!icnl /lrenk with bored pllospllatic nodules in tlu• ' sf ratotype' 1•( tlw Vc,fginn (uppennosl furassic) at Gorodisllclli near Ulynnot•sk, USSR (OVA)

pretend to be representative of a whole unit of the stratigraphical column, however small. Keeping, naturally enough, to the lur.1ssic (since it was the birthplace of stratigraphy), let us take ,,-;a n example the Volgian Stage. Previously this competed with tlw Tithonian (discussed in Chapter 1} for a place at the top of tlw jurassic. A lesser rival was the Portlandian (cum 'Purbeckian') ,,1I ,ngland, to say nothing of the quaintly named Bononian and B11lunitiiytil of Om111 k htll/!ftl/11

-The Process of Sedimentation

87

the edge of the continental shelves, but this is less certain. Even on the ocean floors, however, there are vast areas with"'Ut sediment and great gaps within the sediment that is there. On the main part of the continental shelves, which is the region that chiefly concerns us in the stratigraphy of the continents, the chief contribution of Recent sedimentary studies, in my opinion, has been the demonstration of lateral rather than vertical sedimentation. Modern deposits are not, it seems, laid down layer upon layer over a wide area. They start from a particular point and then build out sideways as in the traditional picture of a delta. In other words, aU bedding is likely to be crossbedding, though often on so gentle a scale as not to be recognisable in the field. It therefore follows that all sedimentary bodies, other than deep-sea oozes and volcanic ash deposits, are likely to be diachronous. This was also one of the main conclusions reached by Alan B. Shaw in his brilliant little book Time in Stratigraphy. Such ideas would seem to contradict the lateral persistence of facies about which so much fuss was made in Chapter 1. But we will return to this point later. Let us consider a simple example from the stratigraphical column to see the implications of my conclusions . In the Sirte Basin of eastern Libya, there are magnificent cliff sections, running literally for hundreds of kilometres, in what is usually referred to as the Marada Formation, of early Mjocene (B urdigalian) age. Tectonic dips are negligible in this region and the winding escarpments, with many isolated 'jebels' or hill outliers in between (Figure 6.1) make possible a detailed investigation of the lateral variations in this so-called formation, on a scale beyond our dreams in more vegetated temperate terrains . In effect, the scru·p has been taken as representing the whole of the Marada unit, since it is commonly capped by a white limestone of post-Burdigalian age and the desert floor below is l ommonly strewn with Lepidocyclina from the Oligocene ( - - -- - ..J

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Figure 6.2 Two possi/Jie i11terpretntions of the relationships /1etwee11 lite different facies of the Maradn Formation, i11 the Mioce11e of the Sirte Basin of enstem Li[llfll

basic environments being preserved simultaneously. In Interpretation 2 (bottom) we have the 'moving finger writes' .1pproach, which was basically the interpretation put forward by the palaeontologist who followed on in this particular research project. He found a certain amount of fossil evidence that the time planes were not parallel with the lithological boundaries .1nd he came to the general conclusion that the facies to the north Me in the main younger than those to the south. Clearly it is difficult to be dogmatic about faunas of this age, when such ·hort time-spans are involved, and it is also difficult to be ::;urc that particular xy : (a) lm11d-made /Jollie far cork; (/J) macllinc-madt• bottle {t>r llll'lal Cll/' (c J ,·,nllt tin tmr willl soldered JOIIIIS a11d IIIIJIYt'sc•rwd 1mper /alwl; (d) cn11 sl'l//c•,/1•11 CIIIIIJ•IIIg 11•rlll /al•d l'rinlecl 011 m!'la/; (c) wit/1 ll'tll of]"mt'la/ (/1111 ((nJ 111 (r/1 ,,,,,., 1/rwt /Wi been pomted ) 97, Ill, 13-1

a rmadillo 38 Asaro, F. 40-41 Asia 11, 13, 27, 119, '126, 130 Assyntian 123 Atla ntic 2, 9, 11, 36, 122-·123,

125-126, 128-131, 136, 140-141 Alias 137 Atrypa reticu/aris

30

a trypids 36 Audley-Charles, M. G. 59, 71, 142 Australia 2, 14-17, 20, 23, 27, 126, 136 Austria 26 Austro-Hungarian Empire 30 Avalo nia n 123 Avery, 0. E. 42 Bacchanalian 107-108 Bahamas 44, 74, 98 Bailey, E. B. 60-61, 71, 76 Bajocian 45, 47, 108 Balkan Mountains 7, 135 Ball, W. H. 111 Barrande, J. ix Barremian 3 Bathonian 31, 45 beer bottles & cans 104-106 belemnites 7, 31, 39 Belgium J, 27 Berry, W. B. N. 142 binomial series 110 Bird, J. M. 142 Birkenmajer, K. 71 Bishop, W. W. 111 bison 38 bivcll\'CS 4, 27, 15, 39, 121 Blow, W II. II I Bm·J,...,, hol!•n 6'1, H'l

146

Index

C on go 23 co no do nt s 35 E. B. 71 So lo ni an "i1 . C on yb ea re , C B on on ia n 51 41 P. 1, r, pe 70 op . C , 35 -3 6, 38, 12 Bortolotti , V xiv 4, 7, 14, 27, 31 na ls vi ra go co ze er H Bosnia127 BotIt riolcp1s 167, 26 -3 3, 35 -3 6, 121 sw ol ds xi, 47 6, 27, 29, 35 -3 7, ot C 5 od op br ac hi 1- 3, 5, 67, 101, C re ta ce ou s Br..iii Mediterranean 61, 123-124, 128-130, 134, 136, 139- 140 Mekong Ri ver 118 Mendips 12, 50 Mercury 36 Merla, G. 72 Meteoritic impacts 36-37 Mexico 5, 10, 31 Meyerhoff, A. A. 143 Michell, H. V. 40- 41

Micmster 1 Middlemiss, F. A. 41 Migliorini 55, 72 Miller, H. 69 Miller, T. G. 111 Miocene 3, 27, 61, 87-90, 137-138,

140 Mississippi (River) 74, 93, 122, 135 Mississippi (State) 2 Mississippian II, 35, 127 Mitchell, A. II. 143 Montana 77 Monte Nuevo 82 Moon 121 Moore, R. C 34 Mordaunt, T. 0. 80 Morocco 9, 15, 31, 6 1-63, 124, 126, 129, 132 MLirchison, R. 68, 107 Napoleon 11-12 nautiloids 7 Neogene 140 Netherlands I Nt•Vc1da 26 Nl·wrtrk Su pl•rgron Jl

IJ

Index

Newell, G. 41 Newell, N.D. 34-35, 38, 4'1-42, 44, 54, 131-132, 143 New England 128, 130-131 Newfotmdland U3-124 New Guinea 48 New York 12 New Zealand 2, 26, 37, 47 Niagaran 18, 123, 125 N ikolov, I. ~4 Noah 32, 39 Normandy 19, 123 North America 20, 23, 30, 38, 65, 123-125 Northern Ireland 1-2 North Sea xiv Norway 20, 79, 123, 130 Nubian Sandstone 21 Old Red Sandstone 15-16, 69, 126 Oligocene 47, 55-56, 87, 138 Oman 139 Ordovician 18-19, 30, 35, 47, 66-67, 109, 120, 124-125 Orinoco River 74 ortbids 36 ostracodes 35 Ostrea 32 Ouachita 130 Oxfordian 45 oysters 32-33 Ozarks 122 Pacific 38, 76, 140 Palaeocene 35 Palaeolithic 106 Palaeo-Tethys 130 Para Zone 110 Passerini, P. 70 Pennines 12 Pennsylvanian 10, 35, 127 pentamerids 36 Peregrine/la 27, 29, 31-32 Permian 9, 13 Persian Gulf 91 pilchards 30 Pitcher, W. S. 111 Pitman, W. C. 143 plants II

149

Plate Tectonics 9, 19, 39-40, 119, 122-123, 126-127, 133, 135-136, 140-141 Plato 79 Playford, P. E. 17, 25 Pleistocene 38, 74, 94, 140-141 Pliensbachian 45 Pliocene 61 Podolia 122 Poland 1, 27, 47, 55-56, 63 Pompeii 82 Portlandian 7, 51-52 Portugal 3, 76 Poubellien 106 Pozzuoli 82-83 Precambrian 20-21, 23, 44, 67, 101 , 123, 130, 135 Princip, G. 102 Proterozoic 123 pterodactyls/pterosaurs 33, 39 Pugh, W. j. Tl Purbeckian 48 Pygope 7 Pyrenees 21, 63-64, 136-137 Quaternary 77, 140 radiolarians 37 Ramsay, A. T. S. 54 Ramsbottom, W. H. C. 111 Rawson, P. F. 41 Read, H. H. xiv Reading, H. G . 143 Recent 86-87, 90-93, 123 Rlwetaviwla co11torta 21 Rhaetian 21 Rhodes, F. H. T. 42, llJ rhynchonellids 36 Rolfe, W. D. I. xii Romania 4, 7-8 Ronov, A. B. 143 rudists 4, 39, 121 Rugosa 127 Ruritania ix Russia 11, 15, 97, 103, 118, 122 Sagri, M. 70 Sand, Ccorgt'

IOH

150

I11dex

Santorini 79 Schindewolf, 0. H. 34, 37, 42 Scholle, P. A. 143 Scleractinia 127 Scotland 15-16, 20, 47, 60, 76, 123-124, 127, 133 Scrape, C. P. 70 Sedgwick, A. 68, 107 Selley, R. C. 95 Shakespeare, W. 52, 86, 121 Shaw, A. B. 87, 96 Siberia 26 Silurian 16, 18, 30, 35, 47, 90-91, 103, 106-108, 113, 125-126, 128, 135 Sinemurian 45 Sittang 118 Skipsey, E. 142 Skolithos 20 Sloss, L. L. 117, 144 Slovenia xiv Sm ith, A. j. 24, 79 Smith, P. J. 142 Smith, W. 47, 68, 110 South Africa 23 South America 20 Soviet Union (former) xiv, 1, 97-98 Spain 3-4, 6, 8-9, 13, 19, 21-22, 37, 47, 61, 63, 128-129, 132, 137, 140 Speed, R. C. 144 Spitzbergen 27, 141 · Spjeldnaes, N. 25, 144 sponges 35 Stalin, J. xiv starfish 30, 38 Stehli, F. G. 144 Stephanian 128 Stevenson, J. 142 Stille, H. 129 Stringocepltnlus burtini 30 stromatoporoids 14, 35-36, 127 stropheodontids 36 Stubblefield, C. J. 111 Styles, P. 141-142 Sujkowski, Z. 54 Sumatra 79 Sutton, J. 144 Svecofennian 128 Swansea 128 Sweden 1, 123 Switzerland 61, 78 Syria 139

Taconian 123, 125-126, 135 Taiwan 58 Tajikstan xiv Tanzania xi, 38 ten taculitids 36 Tertiary 36, 44, 61, 64, 119, 136 Tethys 123, 125, 128, 134, 136 Texas 2, 11, 79, 128 Thailand 21, 118 Thorpe, R. S. 142 Tima11 130 Timor 58-60 tintinnids 6 Tithonian 6- 8, 51, 134 Toarcian 45, 108 Torridonian 20, 123 tortoises 70 Trendall, A. F. 25 Trevor-Roper, H. 40 Triassic 8-10, 13, 23, 25, 28-29, 32, 35, 98-99, 131-133, 139 trilobites 27, 35-36 Trucial Coast 91-92 Trueman, A. E. 25 Triimpy, R. 96 tsunami 75-76 Tw1isia 134 Turkey 1, 26, 58, 139 Turner, C. 142 Turonian 101 Ukraine 122, 126 Urals 122, 130 Urey, H. C. 36, 39, 42 Urgonian 3- 6, 102, 134 USA xiii, 9- 15,21,65-66, 74-75, 78, 103-105, 122-123,126-127,130-132, 135 USSR (former) 11, 51 Van Allen Belt 130 van Straaten, L. M. J. U. 25 Variscan 93, 123, 125, 127-130, 132, 135, 137 Venezuela 74 Venus 36 Vesuvius 82 Vindhyan 20 Vo~hl, P. R. 42

l11dex Voigt, E 95-96, 135 Volga River 122 Volgian 7, 51, 13-l Voltaire, j. F. M. A. 76 Wales 12, 66-67, 105, 124, 131, 133 Wallace, P. x, 25, 111 \Valsh,...Ji. T. 25 Walton, E. K. 144 Waulsortian 127 Wealden 134 Weir, j. 71 Wendt, ]. 45, 54 Wen lock ix, 16, 18, 90, 113, 125

William the Conqueror Wilson, }. T. 144 Wilson, R. C. L. 142 wolf 38 Wollin, G. 84 Woodland A. W. 111 Wright, J. B. 142

19

Yugoslavia (former) xiv, 7-8 Zapll renfls delanouei 32 Zechstein 129 Zoophycos 27

151