Sedimentation in Oblique-slip Mobile Zones: Special Publication 4 of the IAS (International Association Of Sedimentologists Series)

Sedimentation in Oblique-slip Mobile Zones

Edited by Peter F. Ballance Harold G. Reading

BLACKWELL SCIENTIFIC PUBLICATIONS

Sedimentation in Oblique-slip Mobile Zones EDITED BY PETER F. BALLA NCE AND HAROLD G. R EAD I NG

SPEC IA L PUB LI CATION NUM BER 4 OF T H E IN TERNATIO NA L ASSOC IATION OF SE DI MENTO LOG ISTS P U BLI S H ED BY BLACKWELL SC IENT IF IC P UB LI CAT IONS OXFORD LON DO N EDINBURGH BOSTON MELBOUR N E

Sedimenta tio n in

Oblique-slip Mobile Zones

Sedimentation in Oblique-slip Mobile Zones EDITED BY PETER F. BALLA NCE AND HAROLD G. R EAD I NG

SPEC IA L PUB LI CATION NUM BER 4 OF T H E IN TERNATIO NA L ASSOC IATION OF SE DI MENTO LOG ISTS P U BLI S H ED BY BLACKWELL SC IENT IF IC P UB LI CAT IONS OXFORD LON DO N EDINBURGH BOSTON MELBOUR N E

C. Petrol. Geol. 58,1290-1304. HARLAND, W.B. (1971) Tectonic transpression in Caledonian Spitzbergen. GI'OI. Mag . 108, 27-42. HESS, H.H. ( 1933) Interpretation of geological and geophysical observations, Navy- Princeton Gravity Expedition to the West Indies, 1932. U.S. Navy. Hydrographic OfficI'. HESS. H.H. & MAXWELL. J.e. ( 19S3) Ca ribbean Research Project. B/lIf.8rol. Soc. Am. 64, 1- 6. HILL, M. L. & D IOBLEE, T .W. JR ( 19S3) San Andreas, Garlock and Big Pi ne Fa ults, California. Bulf. geql. Soc. Am. 64, 443-4S8. KENNEDY, W.Q. (1946) The Great Glen fault. Q.J. geql. 50(,. u)IId. 102, 41- 76. KINGMA, J.T . (l9S8a) The Tongaporutuan sedimentation in Central Hawke's Bay. N.Z. J. Gl!ol. Geophys. 1, 1- 30. KINGMA, J.T. (19S8b) Possible origin of pierar Inversion Theory towanl Ifle Eslilllatioll of Seismic Sollret Paramelers. Unpublished Ph. D . T hesis, Ca lifornia Institute of Technology. BU.KE. M.C .• JR , CAMPBELL, R.H., DIBBLEE, T .W ., JR. HOWELL, D.G., NILSEN. T .H .• NORMARK, W.R., VEDDER. J.C. & StLVER, E.A. (1918) Neogene bas in formation in relation to plate-tectonic evolution of San Andreas fault sys tem, Ca lifornia . Bll fi. Alii. Assoc. Perrol. GI'OI. 62, 344- 312. BURCHFtEL, B.C. & STEWART, J.H. (1966) ' P ull-apart' origin of the cen tral segment of Death Valley, California. 811f1. Ktol. Soc. Am. 77. 439-442. CHINNERY, M.A . (1961) The deforma tion of the grou nd around surface faults. Bllfl. uismol. SO(;. Am. 51 , 355-312. CHINNERY, M .A. (1963) T he stress changes that accompany strike-slip fa u lting. BIIII. seislllol. Soc. Am. 53, 92 1- 932. CHINNERY, M .A. & I'ETRAK. J .A. (1968) The dislocation fault model with a variable disc::ontinuity. TUlOlwphysics, 5, 5 13-529. CLAYTON, L. (1966) Tectonic depressions along the H ope fault , a transc::urrent fault in North Can terbury, New Zea land. N.Z.J. Oeol. Groph)'s. 9, 95- 104. COUPlES, G. & STEARNS, D .W. (1978) Ana lytica l solutions applied to structures of the Rocky Mountains foreland on local and regional scales. In : Laramide Fo/dillg Ass()Cialt'd ....ilh 8ost'II/t'IIf BI()Ck Falilling ill the WtSlt'rll Ullittd Stall'S ( Ed. by V. Matthews 111). M em. Ktol. Soc. Am. 15 1,3 13-335. CROWELL, J .C. (1914) Origin of latc Ceno:wil; basins in southern California. In: TeclOlliu alld Sedimelltalioll (Ed. by W . R . D ickinson). SpI'C. Publ. Soc. Ceoll. PaleO/II. Miller. TIII.·a, 22, 190--204. ELDERS, W. A ., REX, R. W., MEIDAV, T., ROBINSON, R.T . & BIEHLER, S. ( 1972) Crustal spreading in sou thern California. Scielrce. 178, 15-24. FtSHER, M.A., PATTON, W.W. , JR, THOR, n.R., HOLMES, M .L ., Scorr, E.W., NELSON, C.H. & W ILSON, c. L. (1919) The Norton basin of A laska. Oil alld Gas JOIlr/wl, 71. 96-98. FRElJND, R. (1965) A model of the structural develop ment of Israel and adjacent areas since Upper Cretaceous times. 01'01. Mag. 102, 189-205. F RElJND, R. (1971) The Hope fa u lt, a strike-slip fault in New Zealand. B/lII. N.Z. Keol. Sun. (m'w suits) 86, 49 pp. HARDtNG, T. P . (1976) Predicting productive trends related to wrench faults. World Oil, 182, 64-69. HI LEMAN, J.A., ALLEN, C.R. & NORDQUIST, J .M . (1973) Sl'ismidly of Ihe sOlllhem Cahfornill nKioll, Jalluary I, 1932, to December 1, 1972. Seismological l aboratory, California Ins titute of Technology.

Basil!

de~'elopmelll

by en echelon strike-slip f ail/Is

41

H ILL, M,L. & T ROX EL, B.W . ( 1966) Tecton ics of Death Valley region, California. 8111f. grot. Soc. Am. 77, 435-438. H ILL, D .P., MOWINCKEL, P. & PEAKE, L.G. (1975) Eanhqllakes, active faults and geotherma l areas in the Imperial Valley. Californ ia. Sciellct, 188, 1306-1 308. J"EGER, J.C. & CooK, N .G .W, ( 1969) Fllndanwllfa!:r 0/ Rock M echollic:r. Methuen, London. JENNINGS, C.W . ( 1975) Fault map of Californ ia, Coli/orilla Divl:rloll 0/ Mine:r 01/(/ Gro!ogy Gro!oglc DOlo Mop NI/mlxr I, Scale 1:750,000. JOHNSON, A. M. (1970) Physicol Procene:r III Geology. Freeman, Coopcr & Co., San Francisco. 577 PI'. loFGREN, D.E. ( 1976) Land subsidence and aquifer-system wmpaction in the San Jacinto Valley, Riverside Cou nt y, California-A progress report. J. Rn U.S. geol. SI/r~. 4, 9- 18. LOFGREN, D.E. ( 1978) Salton Trough continues to deepen in Imperial Valley, California (A bstract). £OS, TrailS. Alii. geophys. Vllioll. 59,1051. LoFGRUN, D.E. & R UDIN, M. ( 1975) Radiocarbon dates indicate rates of graben downfa ulting , San Jacin to Valley, Califor nia. J. Res. U.S. ceol. SI/rv. J, 45-46. NORRIS, R.I ., C"RTER, R. M. & TUR NBULL, I.M. (1978) Cainozoic sedimentation in basins adjacent to a major con tinental tran sform boundary in southern New Zealand. J. ceol. Soc. Lolld. 135, 19 1- 205. Q UENNELL, A.M. (1959) Tecto nics of the Dead Sea Rift. 111/. geol. COllcr. 1956. 20, 385-405. RECHES, Z. & JOHNSON, A.M. ( 1978) Develop ment of monoclines: Part II. T heoretical a nalysis of monoclines, In : Loramlde Foldi"g Associoll'd ....ilh Basrmrlll Block FOII/lillg itl lire WeSlem Ulliled Slates (Ed. by V. Matthews III) , Mem. ceol. Sm:. Am. l SI , 273-3 11 . ROOO ERS, D.A. ( 1976) Mechanical analysis of strikes lip faults. I I. Dislocation model studies (Abstrac t). £OS, TrOllS. Am. geopllys. UniOIl. 57, 327. ROOOERS, D ,A. (1979) Vertical deformation, Stress accumulation, and sec;ondary faulting in the vicinity of the T ransverse Ranges or southern California. BI/fl. Coli/omla Div. Milles Grol. 203, 74 pp. S"NfORD, A.R . (l9S9) Analytical and experimen ta l study or simple geological muctllres. 8/111. geol. Soc. Am. 70, 19-51. S"v"OE. I .C. & H,\STIE, L.M. ( 1969) A dislocation model for the Fairview Peak. Nevada, eart hquake. 81111. seismof. Soc. Am. 59, 1937- 1948. SH"RP, R.V. ( 1967) San Jacinto fault zone in the Peninsular Ranges of sou thern Califo rni a. 8111/. geol. Soc. Am. 78, 705- 730 . SH"RP, R .V. ( 1975) En echelon fault patterns of the San Jadnto fault zone. In: Sail Alldrea-f/alill i'l soll/llem Cali/omia (Ed. by J . C. Crowell) Spec. R~p. Colilomia Di~. Mi/les Geo!. 118, 147- 152, WI LCOX, R.E., H"RI)I NO, T.P. & SEELY, D .R. ( 1973) Basic wrench tectonics. 8/111. Am. Ass. Petrol. Geol. 57, 74-96.

Spec. Pub!. into Ass. Sellimell'. (1980) 4, 43- 62

Basin development along tbe late Mesozoic and Cainozoic California margin: a plate tectonic margin of subduction, oblique subduction and transform tectonics

D. G. H OWELL, J. K. C RO UCH , H. G. GREENE , D. S. M cC ULLOC H and J. G. VEDDER

U.S. Geological SUfI'ey, 345 Middlefield Road, M enlo Park, California 94025, U.S. A.

ABSTRACT Along the Californian margin o f the Non h American plate, the configuration and structural stability of late Mesozoic and Cainozoic basins are related to plate kinematics. Three tectonic regimes are recorded; onhogonal high-angle subduction, oblique low-angle subd uc tio n, and transform slip. During the first, regionally extensive forearc basins developed; during the second and th ird, borderland seni ngs formt11 as a consequence of wrench fau lling. In the forearc basins, sedimentological facies constitute regional belts that persist for hundreds of kilometres, wit h strati graphk: sequences that are I- IS km thick. Shorelines are relatively straigh t, shclf facies are broad and well developed, and basin fill is composed of shallow marine, shelf and coalescing submarine-fan facies. Sediment tra nsport in the deeper water facies commonly is parallel to the basin axis. Borderland basins renect tectonic instability. A principal effect of wrenc h tectonics is the vc rt ical reciprocation of crustal blocks. Shorelines are gcnerally irregular, and na rrow shelves pass abruptly into deep basins. Li thofacies change dramaticall y along strike, and stratigraphic thicknesses are variable from basin to basin, from tens of melres up to 6 km. Basin-margin facies are marked by unconformities, slump aprons, lithological pinch-outs and submarine canyon channels. Penecontempora· neous slip a long the basin-margin faults complicates these lithofacies panerns. Borderland type palaeogeography is most extensively developed in the tra nsform tectonic regime, and therefore the more seaward offshore basins are relatively depicted of terrigenous debris owing to transport barriers.

I NTRODUCT IO N

Sedimentary basi n development along the California segment of the North American plate margin can be linked to plate interactions from Cretaceous to Holocene time. Tectonic regimes changed through time in this region. In this paper we shall review the development of sedimentary basi ns that evolved lhrough three 0141·3600/80/0904-0043$02.00

© 1980 International Association of $edimenlologists

44

D. G. Howell el al.

II

SUBOUC T ION

OBLIQ UE SUBDUCTION wllh qenlly d ippinq Btrlioff ZOM Lote Companion ond early Maas tr ich t ian

Turonian (eo. eo m.y. B. P)

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Fig. 1. Schematic plate reconstruction for the California area in the mid-Late Cretaceous and middle and late Tertiary. Figures modified from Dickinson (1979).

California M argin basin del'elopme,,'

45

con trasting ki nematic episodes: subduction, oblique subduction accompanied by strike-sl ip fa ulti ng and transform faulting ( Fig. 1). Subduction and its related processes in western California began in Late Jurassic time. The continental margin that resuiled is infe rred to have been of A ndean type, characterized from east to west by an active continental volcanic arc, a relatively stable and broad fo rearc basin and a dynamic prism of accretionary material ( Hamilton, 1969 ; Dicki nson, 1979). In latest Cretaceous and early Tertiary time, orthogonal convergence changed to oblique convergence (Cooper, Scholl & Marlow, 1976 ; Coney, 1978). The distribution of Early Cretaceous and early Tertiary volcani sm and the associated potassium gradients wit hin the hinterland of t he Cordi llera imply a flatt ening of the eastward di rected Benioff zone as on Fig. 1 (Lipman, Prostka & Christiansen, 1971; Coney & Reynolds, 1977; Cross & Pilge r, 1978; Keith, 1978 ; Lipman , 1980). Consistent with such a model is the Late Cretaceous and ea rl y Tertiary (ca 75- 60 m.y. 1)1') belt of wrench faults along the coast of cen tral Ca lifornia and the development of a proto-San Andreas fault (Su ppe, 1970). The total aggrega te slip during this early phase of wrench faulting is not known, but it was at least 90 km along the east margi n of the Salin ian block (proto-San Andreas fau lt ; Graham , 1978) and it may have been an order of magnitude greater along fau lts west of the Salinian block ( Howell & Vedder, 1978). From a sedimentological viewpoint, the pri ncipal effect of this fa ulti ng was the creation of borderland-like deposi tional sites caused by the spli ntering of a piece of cont inental crust (Salinian block). Eocene sedimentation patterns adjacent to the Salinian block reflect this early borderland setting (Ni lsen & Clarke, 1975). Elsewhere, however, broad forearc sedimentat ion prevailed as in the California Continental Borderland, where no early phase of wrench tectonics is recognizable (Crouch, 1979). By late Eocene time, highangle subduction was agai n well established along the length of the Cali fornia margin . In late Ol igocene time, however, transform tectonic processes began to control sedimentation patterns as the Pacific and North American plates came into contact and the Rivera and Mendocino tri ple junctions migrated south and north respectively (Atwater & Mol nar, 1973). Cumulative slip during the Neogene may be as much as 1000 km on a system of northwest-trending fa ults that span a wi de pliant region of lhe Cali fo rn ia margin. The Sa n Andreas fault system encompasses the entire transform regime, 1200 km long (Gulf of Californi a to the Mendocino fracture zone) and al least 500 km wide (Pacific shelf to within the west part of the Basin and Range Province). The present-day master fault in thi s system is the San And reas fault.

SUBDUCTION REGIME Forearc basin Stratigraphic and sedimentological relations of the Great Valley sequence of central and northern California indicate shel f, slope, and submarine-fan deposition in an elongate forea rc basin from Late Ju rassic through Cretaceous time (Dick inson, 1971; Ingersol l, Rich & Dickinson, 1977 ; Ingersol l, 1978, 1979). Although the original continuity of these rocks has been di srupted by late Cai nozoic tran sform fa ulting, partly equivalent strata are recognized in the Coast Ranges of central California, in

46

D. C. Howell el at. Up,",

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.Jurassic WEST rock s

C3J 8-•• ~ 0

Shelf

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rocks

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rock,

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, , 1",;"1

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m

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EAST

complu

c rutl

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"

Fig. 2. Schematiccross-scction through the forearc basin of the Great Valley sequence showing inferred palaeoenvironmental relations. This large basin system of lit hofacies contrasts with similar lithofacies from smaller, steep-sided basins inferred for the laic Cretaceous borderland of the Satinian block (Fig. 4).

southern California alo ng the western flank or the Peninsular Ranges and in the borderland . Lithological and palaeontological characteristics are similar th roughout this long belt of late Mesozoic strata. Probably the most obvious criteria that differen tiate fo rearc-basi n from wrench-tectonic depositional settings are the regional persistence and great thickness of petrofacies units (Fig. 2). Intrabasi n tectonics generally do not a lter the basin-wide uniformity of depositional patterns. Gradual widening of the forearc basin ( Fig. 3) and progradational and retrogradational cycles (Fig. 2) are uniformly distributed in segments of the forearc basin that are measured in hundreds of kilometres. Most of the Upper Cretaceous flu vio-deltaic faci es form a relatively straight line that can be traced for nearly 1000 km along the western edge of the Sierra NevadaPeninsu lar Ranges crystalline terrain. To the west these facies grade into a parallel bell of inferred shelf strata. Within the deeper parts of the forearc basin, thick successions of submarine fan facies prevail. Lithofacies relations suggest that the fans coalesced and that sediment transport was principally toward the south, along the axis of the forearc basin. In summary, the sa lient characteri stics of the late Mesozoic forearc basin of California and Baja Cal ifornia, Mexico a re: (I) dimensional uniformity measured in hundreds of kilometres, (2) stratigraphic, lithol ogical a nd petrographic uniform ity measured in hund reds to thousands of metres of section, (3) relative tectonic stability resulting in regional regressive or transgressive cycles lasting five million years o r more.

C(I/i/ornia Margin bosin developm ent

41

I nner 1i",11 01 or:crlllionory

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Fig. J. Diagram n:laling the sequential widening of the Cn:taceous fon:arc basin of central and northern California as the subduction zone migrated westwa rd and the magmatic zone migrated eastward. The forearc basin is the Great Valley sequence; numbe rs a re ages in m.y. BP. Figure modified from ingersoll (1978).

OBLIQUE SUBDUCTION Late Cretaceous and Palaeocene borderl and The Salin ian block is an allochthonous ensialic crystalli ne terrane or chiefly relsic plutonic rocks that range in age rrom 110 to 79 m.y. BP (Mattinson, Davis & Hopson, 1971 ; Ehl ig & Joseph, 1977 ; Ross, 1978). This displaced terrai n is bounded on both the east and the weSI by paired belts or the Great Valley seq uence (rorearc complex) and Franciscan assemblage (accretion complex). Upper Campan ian and lower Maastrichtian sedimentary rocks are Ihe oldest strata Ihat li e unconrormably on Ihe Salin ian basement (Howell et 01. , 1977). These strata were deposited in local, restricted basins within a tectonically active terrain ( Howell & Vedder, 1978). Within each basin the

48

D. G. Howell el at.

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, Fig. II . Interpretations made from acoustic·reftection profiles in the outer borderland. Location of profi les shown in Fig. 10. QTpm. stdimentsorlate Miocene to Holocene age; Tm. sediments of early and middle Miocene age: Tmv, Miocene volcanic rocks ; KI-T o, sediments of La te Cretaceous to Olig!Xene age.

southern part, which is compatible with our alternative basin-fo rm ing hypot hesis. Sed imenta ry basi ns that form by wrench fa ulting are chieHy the result of crustal exlension a nd saggi ng as well as folding along braided systems of curvi ng righi-slip fa ults (e.g. Crowell. 1974).

Calijomio Margin basin del'e/opmem

57

Figure 10 illustrates the structural similari ty of the Cal ifornia Continental Borderland to that of onland southern Californ ia . Faults such as the San Andreas, San Gabriel, and Newport- In glewood are well documented right-sli p fault s (Moody & Hill, 1956; Crowell, 1962; Wilcox, Harding & Seely, 1973). Faults offshore are inferred from bathymetry and geophysical data (Moore, 1969; Greene el 01., 1975; Crouch, 1977; Junger & Wagner, 1977 ; Nardi n & Henyey, 1978). Right-slip di splacement along these offshore faults is suggested by en echelon structures and apparent reversals in relative vertical movement along the strike of the fault zone. Palaeogeographic analyses of Eocene and Miocene sequences also suggest lateral displacement (e.g. Howell el 01., 1974). Relatively recent local faulting is indicated throughout much of the region by active seism icity and sea-floor displacemen ts. All of the sedimentary basi ns are close to major wrench zones (Fig. 10) and are typically either rhomboid or lens shaped and are fault bounded on at teast one flank. EI/ echelon folds generally splay into the basins along bordering wrench faults; in some cases, such as along the southwest and western fl anks of Santa C ruz and San Nicolas Basi ns, large-amplitude anticl inoria, instead offaults, form the basin margins. Where wrench faults diverge, adjacent blocks move away from each other to form basi ns (Wilcox et 01., 1973; Crowell, 1974, 1976), such as Patton Basin, Catalina Basi n, and the southern part of Tanner Basin. The sedimentary fill in these basins thickens toward their NNW margins where the fault-bounded block is tipped downward. T he gently slopi ng SE margins of the basins merge wi th faulted and folded structural highs that apparently were uplifted as a result of compression at the convergent end of the block. The NW part of Tanner Basin, San Pedro Basin (Fig. 11 , Line A- A', C-C') and the San Diego Trough may have had a somewhat different structural origin. Judging from interpretations of seismic-refl ection profiles, these basins a re grabens that formed between parallel strands of bordering wrench zones. On land, a simi lar geometry and origin is evident for Devil's Pu nchbowl, which lies between the parallel Punchbowl and San Andreas faults. In contrast to other basins in the southern California region, these fault-bounded basins are narrow and generally have steep flanks. They are characterized by relatively rapid infi lling and complex fac ies relations. Santa Cruz and San Nicolas Basins form a third disti nct basi n type. The NE margi ns of these basins are fault bounded whereas the SW ma rgins are fold bounded (Fig. I I, Line B- B'). Both basins appea r to be syncl inal troughs that are sepa rated from neighbouring basins by broad, ridge-forming anticlinori a. The margins of the two basins are broader and more gently slopi ng than the ot her borderland basins, probably resulting in a generally finer grained, more pelagic basin fill. Basins onshore that formed as a consequence of wrench fa ulting are known to have complex structural and depositional histories. In Los Angeles basin for example, Miocene fau lting, folding and volcanism occurred co ntemporaneously with rapid subsidence and infilling of the basi n (Yerkes et 01., 1965; Crowell, 1974). Within the basin, facies relationships are complex and change abruptl y. Wedges of coarse clastics containing glaucophane schist detrit us were rapidly shed into the basin from adjoining fault scarps to the west, and these deposits in terfi nger wi th and are interbedded with a host of lithofacies reflecting shall ow to deep-water depositi on (Woodford er 01., 1954). Complexities similar to t hose in the Los Angeles basin presumably are present at many places in the borderland . For example, Patton and Tanne r Basins both lie within

58

D. G. H owell er 01.

a block bounded by right-lateral wrench zones (Figs 10 and II). Extensive fau lting, folding and volcanism as well as uplift a nd erosio n of pre-basi n (lower middle and lower Miocene) strata have occurred along the basin margi ns (Crouch, 1977). Younger strata lap onto these older structures and are much less deformed ; however, unconformities within the basi n strata together with fault ing and uplift of basin sediments along the margi ns auest to renewed periods of tectonism during basi n filling. Albatross Knoll (Fig. 10, Li ne A- A'), which separates the two basins, is a local basement block that consists of metamorphic and volcanic rocks. The flat-topped crest of the knoll,

Std imenl fillin~ of e,oded ean1onsPC ~Iorl~ mo .. nq nor ill .

.. 20-17 mybp ConyOn displaced o~q of-canyon o,iqiM les ,.16 mybCl as lower MC, e.h~m(l1 ion of

Movement beq;"s on mb l a~1I zone~7 mybp MC conyon aClive,AC form~ as lowe. MC.

Act ive foul l _ _ Ino(t,ve fault ~:

AClive dro inoqe

PC- Pionte. Conyon AC-Ascension Conyon MC-Monle rey Conyon UN - Unnamed Canyon

head .

Oisplac emrM olon; pc-sq and mb l a~1t zones COnlin~u-uhumalion 01 olt (anyons lakes plocr . ",0·2 mybp

.-".- Modern sl'lO<e! lne _ _ Ancienl shore"ne ~

MC'~

P?-?iqeon Point AN?· Ana NueWl Point M- Montefty PS-?oinl 5Noo!EIoITS OI'OE,ooSi TOOt
9 m) and some can be traced laterally for> 5 km. The calcretes sometimes show classic soi l profiles (Burgess, 1960). The sandstone-with-calcrete division is a sheet-like unit over much of the Midland

74

B. J. Btuck

Valley (Fig. 3) but in the northern region of the Firth of Clyde thins to the SW from ca 300 m north of G lasgow to a few tens of metres in Arran. In the southern part of the Midland Valley it overlaps the older divisions ( Fig. 3) to rest on rocks of the Lower Old Red Sandstone. The sandstones associated wi th this part of the sequence va ry greatly. Some are thi n sheet-like bodies associated with the upward fining units, others are thick , poorly cemented units typified by very large-scale cross-stratification which may be aeolian; yet others have burrows resembling Skolirhos and sandstones of this kind have been interpreted by Chisholm & Dean (1974) as being mari ne. The latter type of sandstones, although present in the west of the M id[and Valley, are more common in the east ; and with the presence of marine Devonian in the central North Sea (Zieg[er, 1975, p. (33) it seems likely that mari ne incursions into the Mid[ and Valley Basin came in from thi s easterl y direction. Sandstone-with-calcrete is also found in Southern Kintyre where it occurs at the top of the seq uence; but when traced northwards it oversteps the underlyi ng sandstone and conglomerate divisions to rest directly on the Dalradian rocks at Galdrings ( McCallien, (927) (see Fig. 4 for locality). This nort herly overstep of the sandstonewith-calcrete division confirms the NE sou rce predicted by the pa laeocurrents in Kintyre. The conglomerates in this division are mai nly quartz and quartzi te bearing, but greywacke of the Southern Uplands appears in the southerly exposu res. The associated sandstones arc quartz arenites (Fig. 9) and th is, toget her with the presence of calcrete in the thinner, more proximal parts of the succession , confirms the curren t view that calcretes mark periods of tectonic stability.

PALAEOGEOGRAPHY AND STRUCTURAL FRAMEWORK

The Upper Old Red Sandstone was deposited in two embaymen ts: the Midland Valley Basi n (stratigraphically a basin but palaeogeographically an embayment , see Sluck, 1978, p. 272) which opened to the east and northeast; and the Kintyre embayment, the shape of which is not known but which opened to the southwest. Both have palaeocurrent orientations parallel to the Highla nd Boundury Fault and to the other structures in the older rocks flunkin g th e Mid land Valley (see Fi gs 4 and 12). The upland zone separating the Midl"."J:"J , •• "'''1'(0 .... ",,[0 ~ ( 0 _ ........"

,.. "" "OX1JlH1{O'

,.t...

D ...,...."" _"~Al """" ..... ",'0'''5 ~

~

010'-""" c....... ~, .,.., c...."", ..""",.

,,_0 st.....

Fig. 6. Map of a segment of the northern edge of Hornelen Basin (loo:;:ated in Fig. 5). Conglomeratic fans inlerfinger with a belt of floodbasin/lacustrine fines which in turn pass southwards into the coarser, fluvial sediments of the axial region (from V. Larsen, unpublished data),

of upward coarsening and thickening wedges of alluvial fan (when interfingering with subaerial flood basin/fl oodplain deposits) or fan delta (interfingering with lacust rine deposits) origin. The segment of the northern margin shown in Fig. 6 contains more than twenty-five such fans. In general, the fans along this margin are dominated by conglomeratic and sandy sediment gravity flows. Details of such deposits together wi th their organization and relationship to the impinging flood basins have been documented by Larsen & Steel (1978). Fan deltas have been recognized by identification of beach gravels in the fan sequences (Gloppen, 1978), by the presence of debris flows with anomalous (high) bed thickness/ maximum particle size ratios or matrix content across the lower fan reaches, and by conglomerates showing textural inversion due to rigorous mixing, slumping and sliding into the adjacent lacustrine fines. Internal details of an alluvial fan which interfingers with flood basin seq uences along this margin , are shown in Fig. 7. The subaerial nature of this fan ( Hjortestegvatnet) is suggested by the dominance of streamflow and sheetflood conglomerates around the toe reaches, in contrast to the sheetlike, graded, subaqueous sediment gravity flows on the toe of

R. S teel and T. G. Gloppen

88

m

PROGRAD ING AUlNIAl FAN

" AGGRADING FlOOO9AStN

BED TYPES and SEDIMENTATION UNITS

Fig. 7. Details of the interfingering between Hjortestegvatn Fan (Iocaled in Fig. S) and the impingi ng floodba sin deposits, together wit h a summary of bed types and sedimenlalion un its (after G loppen, 1978).

the fan delta described by Larsen & Steel (1978). When mapped, it is clear that the upwards coa rsen ing in the Hjortestegvatnct conglomerate body (....... 200 m th ick) is exactly laterally equivalent to a correspondi ng upwards coarsening in the coarse sandstone of the axial flu vial system fa rther sout h ( Fig. 8), despi te the fact that the conglomerate and sandstone derive from different dispersal systems. In addition a belt of intervening mudstone, si ltstone and fi ne sandstone (fl oodbasi n) wedge out nort hward, southward and upward (Fig. 8). It is evident that the upwa rd coa rsening mot if is basinwide (i ndependent of facies), i.e. an important argument for its tectonic origin

Llite Co/a/onion basin formation

89

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WESTPHALI AN

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NAMUR IAN

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Astorian

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Namurian C Namurian B Namurian A l2S

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Sudetic or Palentian

Hercyniall 10 late Hercynian continenlal strike-slip syslem

11 3

Asturian coalfield, and possibly other Stephanian A-c coal basins (Wagner, 1970, 197 1a ; Corrales, 197 1; Kn ight, 1975 ; Heward, 1978a, b). It is apparent from the palaeogeograph ical maps (Fig. 2) that there were periods of basin initiation during the Namurian C- Westphalian A, Westphalian A· B, Westphalian D- Cantabrian and Stephan ian A-C (Table I). There is a general trend in which Carboniferous deposits become younger and increasi ngly continental towards the southwest. Shallow-marine carbonate and marine basi nal deposits are dom inant d uring Namurian and lower Westphalian to be superseded by marginal-marine and nonmarine clastic deposits during Westphalian D and Stephan ian. In addi tion to a dominant and persistent supply from south of the present Cantabrian Moun tains, local clastic sed iment so urces operated at different times.

Fold phases, unconformities and disconformities Slrat igraphic subdi vision of the Upper Carboniferous ha s emphasized up to four major phases of deformation and unconformity (Table I) (de Sitter, 1962, 1965 ; de Sitter & Boschma , 1966 ; Boschma & van Staalduinen, 1968 ; Wagner, 1966, 1970; Wagner & Martinez-Garcia, 1974). These phases are spectacula rly developed locally, bu t their timing is often imprecise. Th ick conglomerates which overlie unconformities havc been interpreted as postorogenic deposits and correlated with other conglomerates not necessarily overlying unconform it ies, so t hat they appea r to have a great regional extent. In detail these ' major' phases of deformation and unconform ity are variable in extent, timing and significance and there are a large number of other fold phases, unconformi ties and discon formit ies. The presence of thick conglomerates merely indicates proxim ity to upli fted source areas. In northern Palencia (Fig. 1a), for instance, the type region for the Palenrill1l phase, there are Namuria n B-C, Namurian C and Westpha lian A unconformities prior to the emphasized Westphalia n B (Palentian) phase of fo ldi ng and erosion (Wagner & Wagner-Gentis, 1963 ; Wagner, 1971 b; Wagner et aI., 1971). The Palcntian unconform ity is overlain by the thick Los Cintos Conglomerate. Attempts have been made to correlate the Los Cintos conglomerate with the Curavacas Conglomerate which also overlies an unconformity, and thus ascribe to it a regional significance (de Sitter & Boschma, 1966; Boschma & van Staald uinen. 1968; Wagner, 1970 ; Wagner & Martinez-Gard a, 1974). T here were and remain doubts whether the Westphalian B Los Cintos Conglomerate is time-equivalent to the Cu ravacas Conglomerate, or whether the enormous accumulation of the latter is Westphalian A and perhaps follows a Westphalian A phase of deformati on (Wagner, 1970 ; Wagner & Martinez-Garda, 1974). To the west of Palencia, in the province of Le6n, a disconformity occurs loca lly between basal Westphalian A and Westphalian B deposits (Moore et 01. , 197 1) and , sou th of the Le6n Line, thrust and nappe movements occurred some time between Namurian and Westphalian D (J. Ru pke. 1965; de Si tter. 1965 ; Jul ivert, 197 Ia) ; in Asturias there is no evidence of Westphalian B deformation (Ju livert, 197Ia) ; in southern Santander Maas (1974) describes a number of unconformities and disconform ities; and in northern Santander there is a major NamurianWestphalian D discon form ity. Thus the Westphalian B ' Palentian phase' can only be demonstrated in northern Palencia. Elsewhere, although unconformities have been

114

A. P. Heward (Inti H . C. Readillg

equated with the Palentian phase. there is no firm evidence thaI they occurred during the Westphalian B. The effects of the upper Westphalian D L eOlliafi phase are only clearly seen in northeastern Lc6n, where Westphalian B to lower Westphalian 0 deposits were deformed and eroded prior to accumu lation of Upper Westphalian D conglomerates (Wagner, 1970 ; Wagner & Ma rtinez-Garcia, 1974). Elsewhere, the upper Westphalian D phase has been equated with refo lding, and with a number of di sconfo rmable palaeo-karst surfa ces in li mestones in northern Palencia (Wagner et aI., 1977); however folding here du ri ng Westphalian D time cannot be directly demonst rated. The ASllIriall phase includes a number of spectacu lar unconformities below conglomeratic successions whose bases range in age from Stepha nia n A-C. In northern Palencia there is evidence of the timi ng of deformati on, where Cantabrian to Stephan ian A sediments of the Barruelo coal field were isoclinally folded prior to the accum ulation of late Stephanian B deposits (Wagner & Winkler Prins, 1970). However, there is little difference in the age of floras from the pre-deformation succession of the Barruelo coalfield a nd from the post-deformation Stephan ian succession in the Sabero coal field, 70 km to the west ( Fig. Ic; Kni ght, 1975). Elsewhere the tim ing of deformation is uncertain but the onset of Stephanian sedimentation occurs progressively later in a westwards di recti on fro m Sabcro (Wagner, 1970). T hus it seems improbable that there was a synchronous 'Asturian phase' of deformation but rather that deformation affected one area whilst sed imentation occurred in a nother. Little is known of the Saalian or Ura/ian phase(s) of deformation except that Stephanian A-C deposits were folded prior to the Perm ian (de Sitter, 1965; Wagner, 1970).

Thus throughout the Upper Carboni rerous, whilst it is probable that some periods were characterized by more intense deformation tha n others, the overrid ing impression is that deformation and erosion occurred con temporaneously with sedimentation close by (Maas, 1974 ; Reading, 1975; Savage, 1979). Structural style The Cantabria n Mountains are characterized by E- W trending structu res wh ich become orientated to a N- S direction towards the west as the Asturian arc is approached (Fig. I b a nd c). Deformati on is intense, with extensive thrusti ng a nd overtu rni ng, but is essentially superficial with metamorphism absen t and cleavage only locall y developed. The presence of highly competent horizons such as the Cambro-Ordovician quartzites and Upper Carbonirerous conglomerates a nd limestones interbedded with incompetent horizons such as the Cambrian and Lower Carbonife rous nodu lar limestones a nd shales, known as 'griotte', leads to widespread decollement and disharmonic fo lding. A diversity of structural style includes thrusts a nd na ppes, possibly gravityinduced, folds and refolded folds, resulting from both vertical movemen ts a nd from lateral compression, a nd gravity-induced flap and cascade folds . Structures rarely conform to the patterns of a classical com pressive orogen and vertical movements appear at least as important as laterally com pressive ones. T he sporadic development of cleavage em phasises the local nature of stress fields res ponsible for much of the deformation (Savage, 1979).

Hercynian

(0

t(lfe Hercynian continl/m(ll strike-slip system

liS

A large number of nappe and th rust slices have been described (de Sitter, 1962, 1965; J. Rupke, 1965; Sjerp, 1966 ; Evers, 1967 ; van den Bosch, 1969; Jul ivert, 1971a, b; Wagner, 1971b; van Staaldu inen, 1973 ; Maas, 1974 ; Savage, 1979). Nappe movemen t and thrusting occurred from the south, west and north at a number of periods during the Upper Carboniferous (Fig. 3a). Estimates of the extent of horizontal moveme nt are of a few kilometres- few tens of kilometres (Jul ivert, 1971a ; Wagner, 197 1b; Maas, 1974). The converging cen tripetal pauern of nappe movemen t is atypical of classical orogenic belts and gravity has been considered the only possible driving force (Savage, 1979), alt hough Julivert (1971a) favoured basement control. Nappes and thrust sheets have been refolded along E- W and , less common ly, N- S axes. Most Upper Carboniferous deposits occur in E- W oriented syncli nes or in syncl ines which skirt the Ast urian arc. The predominant E- W orientation of fold ing persists throughout the Upper Carboniferous (de Sitter, 1962, 1965 ; Wagner & Marti nezGarcia, 1974; Savage, 1979). Savage (1967) and Maas (1974) consider that the synclines they analysed formed by vertical movement of fa ult defined basement blocks rather than by N- S compression, although Maas also documents compressive folding. In the well known (because of mining) southern Cantabrian Moun tain coa lfield synclines, the northern limbs arc relatively complete and the southern limbs are thrust out indicati ng some S- N compression ( Figs Ic, 3b; Wagner & Winkler Prins, 1970 ; Wagner, 197 1a; Knight, 1975). In the less well known sed imen tary basins of the northern Can tabrian Mountains the nort hern limbs have been thrust out (MartinezGarcia & Wagner, 1971). Grav ity-induced flap and cascade folds and collapse fau lts resulting from instabil ity of uplifted weakly consolidated sed iments aTe common features of thick Upper Carboniferous marine basinal successions and also some of the Picos de Europa nappes (Fig. 3a, c ; Savage, 1967, 1979 ; Maas, 1974). In the latter case, tectonic transport accompanyi ng gravity folding is from S to N, con trasting to the direction of nappe movement. Flap and cascade folds have horizontal axial planes and orientations which refl ect underl ying topography. Maas (1974) in describing thick basinal deposits suggested a continuum from synsedimentary sl umps and olistostromes, to later flap and cascade folding and collapse faulti ng. The major structural lines or zones of Figs Ic and 2 (Cardai'io, Leon, SaberoGord6n Lines and similar smaller fea tures) are points of contention between those who believe them to be latc Hercy nian fractures which have subsequently been react ivated (e.g. Marcos, 1968; Wagner, 1970 ; Julivert, 1971b; Moore et at., 1971 ; Wagner & Martinez·Garcia, 1974), and de Sitter and co-workers who suggest that they controlled mid- Devonian-Upper Carboniferous sed iment distributions and also influenced Upper Carboniferous deformation (e.g. de Si tler, 1962, 1965; de Si tler & Boschma, 1966 ; Savage, 1967, 1979; Boschma & van Staa ld uinen, 1968; Kullman & Schl)nenberg, 1978). Assessment of the sign ifica nce of these feat ures appears warranted. Metamorphism and igneous activit y Metamorphism in the Upper Carboniferous and underlyi ng Palaeozoic succession is generally absent or of low-grade greenschist facies (van Veen, 1965; LobatoAstorga, 1977 ; N. A. Ru pke, 1977). Upper Carboniferous igneous rocks are rare and deeply weathered at surface exposures. Most occurrences are close to major fault lines.

A. P. Heward ami H. G. ReatJillg

116 o.

"

I

,,,,... do r,,, _ _ , C_oI>t"""SI~_

.... ....." oM ;.to'"..; ...... h _ ~

, _. ...... "'--"' I)o/h

)' ig. 4. Palaeo-tectonic map of the: late Hercynian. aftcr Arthaud & Malle ( 1977).

an unknown extension ( Fig. 4). The Urals, Mauritanides and Southern Appalachians form ed as compressive orogenic belts at the ends of this shear zone. The BiscayNorth Pyrenean fault , running parallel to the north coast or Spain , is one of the first-order strike-slip systems within this shear zone with appr oximately 150 km of dextral offset. Between the tim-order dextral strike-slip systems, there arc regions wi th smaller conj ugate wrench fault s, th rusts, rolds and sed imentary basins. It is within such a region that the Upper Carboniferous deposi ts of the Cantabrian Mountai ns accumulated and were defo rmed.

118

A. P. He word(//UI H . C. Reading

Evidence ror \'crlical movements Most strike-slip fault s have a componen t of dip-slip movement a nd normal faults are abu ndant within strike-slip systems. It is this vertical movement that leads to the proximi ty of uplifted source areas and sed imentary basins (Kingma, 1958 ; Lensen, 1958 ; Clayton , 1966 ; Crowell, 1974a, b). Rapid uplift and subsidence result in thick sed imentary succession s (e.g. > 1000 m of Quaternary sediments, Hanmer Plains, Hope Fau lt, New Zealand, Freund, 1971 ; > 12000 m of Mi ocene-early Pleistocene sediments, Ridge Basin, California, Link & Osborne, 1978) and very high sedimentation ra les (0-4--1 '5 m/ IOOO years, Schwab, 1976; Miall 1978). Uplift of weakly consolidated sediments can cause gravity deformation ( Babcock, 1974). N umerous features of the Upper Carboniferous deposits of the Cantabrian Mou ntainscan be attributed to ra pid vertical movements and to the proxim ity of source a reas and depositional basins. Abrupt thickness a nd fa cies changes; th ick, rapidly acc umulated , basinal and shelf successions; repetitively thick regressive and transgressive sequences; the vertical stacking of deltaic environ ments in the Gua rdo-Cervera coalfiel d (Fig. Ic; Heward, unpublished, cf. Fisher & McGowen, 1969) and the vertical stacking of a lluvial fa n mega sequences (Heward, 1978b; cf. Steel, 1976; Steel & Aasheim, 1978); the presence of loca lized uncon form ities a nd disconformities and common gravity induced deformation are consistent with ra pid vertical movements. High sedimentation rates, time-equivalent sedimentary successions and adjacent unconformities, ubiquitous conglo merates and basin margin deposits, and nUmero us local so urce a reas refi ect the proximity of source a reas and depositional basins. Approximate sed imen tation rates were up to 0·36 m/ IOOO years. These are high for many types of sedimentary basin bu t are low com pared to recent strike-slip basins (Schwab, 1976 ; MiaH, 1978). This may be due to uncertainty and approximations of dating, and the di ffi culty of determinin g the length of phases of non-depositio n and erosion which separate phases of sedimentati on. On the other hand such rates may simpl y refi ect smaller lateral movement within these Hercynian strike-slip belts as compared with movements o n the Tertiary Sa n A ndreas and Alpine fau lts.

Evidence for latera l movements In Recent and Tertia ry strike-sli p fault systems, latera l movement can be demo nstrated by the offsetting of geomorphological features, by the mismatch of present source areas and depositi onal basins, by the offsetti ng of originally continuo us lithologies a nd depositional systems, by the recognition of conglomerates strewn along fau lt lines, by reconstruction of plate movement by use of magnetic anomalies and by the occu rrence of synchrono usly form ing zones of uplift and of subsidence along cu rving, offsetting and splaying fault systems. In the Upper Carboniferous deposits of the Cantabrian Mountains the direct identification of lateral movements is hindered by the complexity of the geology, by rapid facies changes a nd by the regio nal extent and lack of distinctive lithologies within the underlying Pa laeozoic source rocks. However, a t o ur present state of knowledge, which still lacks much detailed sed imentology, two basins a re known where it is unlikely Ihat deposits were derived from the regions wilh which they are now juxtaposed. The Tejerina syncline at the northern end of the Valderrueda coal field (Fig. Ie)

Hercynian ro fare Hercynian cominenral strike-slip sysrem

119

contains more than lIDO m of clast-supported conglomerates and coal-bearing sandstones and shales of lower Cantabrian age (Wagner, 1978 personal commun ication; Fi gs 2e, 5a). Cross-bedding and clast imbrication within these all uvial fan deposits indicate a source to the NW. The traceable downcurrent extent of conglomerate beds implies accum ulation on alluvial fans having a radius of > 7 km and an approximate fan area of 75 km 2• Conglomerate clasts suggest a source area consisti ng of CambroOrd ovician quartzites, Devonian limestones and sandstones, Namurian Caliza de Montana and a minor contribution of lower Westphalian limestones and granulestones (van Loon, 1972 ; Goester, 1973). One 60- 120 m conglomerate ex tendi ng downcurrent > 7 km consists almost exclusively of Cambro-Ordovician quartzite clasts. No multicycle conglomerate clasts (Tanner, 1976) have been observed. 0.

Teje,ino Syncline N

) r'>J ":.~'

\

CCJc:IIO; C' O lSIaI••

_ A:>Iao,oic· OJ] L W..,phoI;a.> 8

I

1'bIotaCK, E.A. ( 1914) Geology of the northeast margin of the Salton Trough, Salton Sea, California. Bull. geol. Soc. Alii. 85, 321 - 332. BARD, J .P., CAPDEvn..... , R., MATIE. PH. & RIBEI RO, A. (1973) Gcotectonic model for the Ibe rian Variscan orogen. NOlllre ( PII>,s. Sci.), 24 1, 50-52. BELT. E.S. (1969) Newfoundland Carboniferous stratigraphy and its relation to the MaritimCS and Ireland . In: North Allalllic-G('ology {/luI COli/iIII'll/III Dr/II (Ed. by M. Kay). 1'111'111. Alii. A55. Pt'trol. Gl'ol . 12,734-153. B...... KE. M.e.. JR. CAMPBELL, R.H .• DlD8LEE. T .W.• JR. HOWELL. D.G .• NtLSEN. T. H., NORMARK, W.R., VEDDER, J .C. & SILVER, E.A. ( 1978) Neogene basin forma ti on in relation to plate-tectonic evolUlion of San Andreas faul t syStem, Califo rn ia. Bllfl. Alii. Assoc. PClml. Geol. 62, 344- 372. BLESS, M J.M . & WINKLER PRINS, e.F. ( 1973) Palaeoecology of Upper Carboniferous strata in Asturias (N. Spain). c.r. 7th COllgr. Av. Slr(1l. gial. Carbon .• Krefel d 197 1, 11, 129- 137. BoscH, W.J. VAN DEN (1%9) Geology of the Luna- Sil region, Cantabrian Mountai ns (NW Spai n). L t'i(/st! geol. MI'(/('(I. 44, 137- 225.

BoscHMA, D. & STAALDUINEN, C.J . VAN ( 1968) Mappable units of the Carboniferous in the sou thern Cantabrian Mountains. uidse grot. M t'ded. 43, 221- 232. BoWMAN, M.B.J . ( 1919) The de posi ti onal environments of a limestone unit from the San Emiliano Forma tion (Na muria n/Wcstphalian ), Cantabrian Mts., NW Spnin. Sedilll/'llf. Geo/. BULL, W.B. ( 1917) The a lluvial fan environment. Prog. P"Y~. Geogr. 1,222-210. C ...... YTON. L. ( 1966) Tectonic depressions along the Hope fault. a transcurrent fau lt in North Canterbury, New Zealand. N.Z. J. Gt'Q/. Gl!Op/I)'~. 9, 95-.104. CORRALES. I. (197 1) La scdimentaci6n durante el Estafaniense D-C en Ca ngas de Narcca. Rengos y Vi!lablino (NW de Espa na). Tmb, Geol. O"il!do, 3, 69- 13. CROWELL, J.C. (1974a) Sedimentati on along the San Andreas fault, California. In : Mode", 01/11 Allcien! Gt'Qs)'IldiIlO/ Sniimt'IIWfioll (Ed. by R. H. Doll JR & R. H. Shaver). Spl'c. Publ. Soc. eroll. Po/roll/ . Miner .• Tlllsa, 19, 292- 303. CIIOWELL, J.C. (J914b) Origin of laiC Cenozoic basins in Southern California. In: Tec/I)IIics olld Sl'diml'lIWfioll (Ed. by W. R. Dickinson). Spl'c. Pub/. Soc. eroll. PO/I'OIll . MilH'r, Tu/so, 22, 190--204. DE JONG, J. D. ( 1971) Molasse and clastic-wedge sed iments of the sou thern Cantabrian Mou ntains (NW Spain) as geomorphological a nd I;!nvironmental indicatOn;. G('o/. Mijl/b. SO, 399-4 16. DE MEIJ ER. J.J . ( 1971) Carbonate petrology of algal limestones (Lois-Ciguera Forma tion, Upper Carboniferous, Le6n. Spain). Leidse gt'Ol. Met/I'd. 47, 1- 9 7. OF. SITTER, L.U. (1962) The Hercynian orogenes in northern Spain. 1n: Soml' Aspl'Cfs of 111f' VI/r iscoll Fold Belt (Ed. by K. Coe), pp. 1- 18. Univen;ity of Manchcs ter Press,

Hercyniall to late HercYlliall COlllillefl1al strike-slip system

123

D E SITT'ER, L.U. ( 196:5) Hercynian and al pine orogenies in northern Spain. Cwl. MiJllb. 44, 373- 383. DE SITTER, L.U. & BoscHMA, D. (1966) Expla nation geological map of thc Palaeo%oic of the southern Camabrian Mounta ins, I ::50,000. Sheet 1 Pisuerga. uid.s~ leol. M~d~d. 3 1, 19 1- 23g. D EWEY, J .F. & BUR KE, K.C.A. ( 1973) T ibetan. Variscan and Preca mbr ia n basement reactiva tion : products of continen tal collision. J. Ceol. 81, 683-692. DVORAK, J .• M IROUSE, R., PA PROTH, E., PELHATE, A., RAMSBOTTOM, W. H.C. & WAGNER, R.H. ( 1977) Relations entre la sedimen tation Eodevono-Carbonif~re et la tectonique Va risq ue en Europe Centrale et Occidentale. In: La C/r6illl!' Vari.sqll~ d'£Urope Moyelme n Oet:idell/a/~. Coli. ill/I'm. CNRS, Remres, 143, 24 1- 273. ERX LEBEN, A.W. ( 197:5) Deltaic and rela ted carbonate systems in the Pen nsylva nian Canyon Group or north-«Iltral Texas. In: D~/fO:r, Modl'/:r for ExploratiOIl (Ed. by M . L. Broussard), /lousto/r Ceol. SI)C. 399-42:5. EVERS, H.J . (1967) Geology or the Leonides between the Bernesga and Porma rivers, Canlabriall Mounlains, NW Spain. Leidse Keol. Meded. 4 1, 83- ISI. FISHER, W .L. & MCG OWEN, J.H. (1 969) Deposi lio nal sys tems in the Wilcox G ro up (Eoce ne) of Texas and their re lati o nship to oceu rrence of oil and gas. Billf. Am. A ss. PeITol. Ceol. 53, 30- :54. FLORES, R.M. (1 975) ShOrl-headed stream del ta: model ror Pennsylvanian Haymond Formatio n. wes t Texas. 8 1111. Am. Ass. Pnrol. Geol. 59, 2288- 2301 . FREUND, R. ( 197 1) T he Hope rault, a mi ke-s lip fault in New Zeala nd. BIlIl. N.Z. geol. SlIr~. 86, 49 pp. GARCIA-LoYOORRI, A., ORTUNO, G ., C... RI DE DE l1 NAN, C., G ERV ILLA, M ., GR EBER, C H. & FEYS, R. (1971) EI CarbonIfero de la Cuenca Central Astu ria na. Trab. Ceol. O~'iedo, 3, 10 1- 150. GINKEL, A.C. VAN (196:5) Spanish Carboniferous fusulinids and their significance for correlation purposes. uidst Iwl. MednJ. 34, 172- 225. GOESTER, F. ( 1973) St'dimelltalogie vall Cea-AfzefTiligell: bij TejeTliw (pra~. Leo". Spa/vel. Unpublished M .Sc. T hesis. Uni~ersity of Leiden. G RAAff, W.J .E. VAN DE (l97 Ia) T hree Upper Carbonifero us, limestone-rich, high-destroetive della systems. with submarine fa n deposits. Ca ntabrian Mounla ins, Spain. uidse Keol. Meded. 46, 1:57- 23:5. GRAAff, W. J.E. VAN DE ( 197Ib) T he Piedrasluengas Limestone, a possible model of limestone facies distribution in the Ca rboniferous or the Cantabrian Mountains. Trab. Grol. O~;ello, 3, I SI- I :59. H ARLAND, W.B. (19 71 ) Tectonic transpression in Caledonian Spitzbergen. Geol. Mag. 108, 27-42. H ELMIG, ~I .M. (196:5) The geology of the Valderrueda. Tejerina, Ocejo and Sabero coal basins (Cantabrian Mountains, Spain). Ltidse Keol. Meded. 32, 75-149. H EWARD, A.P. ( 1978a) Alluvial fan and lacustrine sediments from the Stephanian A and B (La Magda lena. Cii'lera·Matal1ana an d Sabero) coalfields, northern Spain. Sed/melllalaIY, 25 , 45 1-488. HEWARD, A. P. ( 1978b) Alluvia l fan seque nce a nd megasequence mo dels: with examples from Wes tphalian D·Stephanian B coal fields, northern Spain. In : Fili vial Sedimentology (Ed. by A. D. Mia ll), MI!'III . ell/r. Soc. Petrol. Ceol. 5, 669--702. HOO KE, R. LE B. & R OHR ~ R, W.L. (1 977) Relal ive erodibili ty of so urce-a rea rock types, as delermi ncd from second·order varia tions in allu vial fa n size. Bull. geo/. Sac. Alii. 88,1 177- 11 82. JOHto:SON, G. A.L. ( 1973) Closing of the Ca rbon ifero us sea in wes tern Europe. In: ImplicatiollS of Clmtilll'lI/al Drift fa tire Eartlr Sciences (Ed. by D. H. Tarl ing & S. K . Ru neorn), pp. 843- 850. Academic Press, London. JULIVERT, M. ( 197 1a) Decollemen t tectonics in the Hercy nia n Cordillera of northwest Spain. Alii. J . Sci. 270, 1- 211. J ULIVERT, M . (197Ib) L'tyolu tion structurale de rare asturien. In: HisfOire Slfuctura/e du Colfe de Gascagnt. Frullra;s Pelf. Col/oqlles et Simi/raires, 22-1, 1- 28. Kt NGMA, J .T . ( 19S8) Possible origin of piercement stroc tures, local uncon formi ties and secondary basins in the Eastern Geosyncline, New Zealand. N. Z . J. Geol. Ceop/ws. 1,269- 274. KI.EIN, G . DE V. (1974) Esti mating water depths from analysis of barrier island and deltaic sedimentary sequences. Geolog)', 2, 409-4 12. KN IGHT. J.A. ( 197:5) The: syslemmirs alltl stratigraphic aspects of lire Sltphanian /fora of lire Sabero roolfield. Unpublished Ph.D. Thesis, Universi ty of Sheffield. K RAfT, J.C. ( 1971) Sedimentary facies patterns and geologic history or a Holocene ma rine trans. gression. BIIII.leol. Soc. Am. 82, 213 1- 2158.

"ISt.

124

A. P. Heward and H. G. Reading

KULLMANN, J. &. ScHONENllEII.G. R . (1978) Facies differentiation caused by wrench deformation along a deep-seated fault system (Le6n line, Cantabrian Mountains, Nort h Spain). TUlolwpliysics,

48, TI S-T22. LAURENT, R. (1972) The Hercyn ides of sou th Europe, a model. PrM. 24,11 /111 . K~f. COIIKr. MQl1fr~/,

3,363-370. LENSEN, G .1. (1958) A method of graben and hors! formation . J. Grof. 66. 579-587. LE PICHON, X., SlOun, J .C. &. FIlANCHETEAU. J. ( 1977) The fit of the continents around the North Atlantic ocean. Tec/OIwphysics, 38, 169-209. LINK, M .H . &. Os80IINE, R. H . (1918) Lacustrine facies in the Pliocene R idge Basin Group: Ridge Basin, California. In: ModemalldAncientLake Sedlil1(.llIs (Ed. by A. Matter & M . E. T ucker),

Spec. PI/bl. ilil. Ass. Sedimelll. 2, 169-187. loDATO ASTOIIO,ol.. L. (1977) Geologia de los valles altos de los rios £SIll, YIISO, CarriOIl y Dt!.va. Unpublished Ph. D . T hesis, University of O viedo. LooN, A.J. v ... N ( 1972) A prograding deltaic complex in the Upper Carboniferous of the Cantabrian Mountains (Spain): The Prioro-Tejerina basin. Leidst!. geo!. Me(kd. 48, 1-81. loWELL, J.D. (1972) Spitsbergen Tertiary orogenic belt and the Spi tsbergen fracture zone. BII/I. geol. Soc. Alii. 83, 3091 -3 102. . M ... .u, K . (1974) The geology of Liebana, Cantabrian Mounta ins, Spain: deposition and deformation in a flysch area. LefdJ'e goof. Meded. 49, 379-465. M ... RCOS, A. (1968) Nota sobre el significado de [a 'LeOn line'. Brevoria gool. ASlur. 7, 1- 5. M ... RTINEZ·G ... RCIA, E. ( 1971) The age of the Caliza de Montana in the eastern Cantabrian M ountains. Trab. Goof. Ol'iedo, 3, 267- 276. M "'RTtNEZ·GARCIA, E.• CoRRALES. I. & CARBALLEIRA. J. (197 1) EI flysch carbonifero de Pcndueles (Asturias). Trab. Goof. Oviedo, 3, 277-283. MMI,TINEZ·G ... RCIA, E. & W"'GNER, R.H. (1971) Marineand continental deposits of Stephanian age in eastern Asturias (NW Spain). Trab. Geol. Oviedo, 3, 285-305. M ... TTE, PH. ( 1968) La structure de la virgation hercynienne de Galice (Espagne). Tra~. Lab. Giol. Fac. Sci. Univ. Gre/wble, 44, 1- 128. McGOWEN, J .H . ( 197 1) Gum H ollow fan delta, Neuces Bay, Texas. Rep. Invest. Bllr. ecOIl. GI!OI. Te)(as, 69, 91 pp. McGOWIN, J.H . & ScoTT, A.J. (1974) Fa n-delta deposition: processes, facies and stratigraphic analogues. (Abstr.) AI/n. MIg. Am. As.s. Petrol. GI!OI. 60-61. Mt ... LL, A .D . ( 1978) Tectonic and syndeposi ti onal deformation of molasse and other non marineparalic sedi mentary basins. CUll. J. Earll! Sci. 15, 1613- 1632. MOORE, L.R., NEVES, R ., WAGNER, R. H . & w ... GNER-G ENTIS. C.H.T. ( 1971) The s tratigraphy of Namurian and Westphalian rocks in the Villamanfn area o f northern Le6n, NW Spain. Trab . Geol. Oviet/o, 3, 307- 363. NILSEN, T .H . (1978) Late Cretaceous goology of California and the problem of the proto-San Andreas fault. In: Mesozoic Palaeogeography o/the W/,slem Vlliled SI(ltes (Ed. by O. G. Howell & K . A . McDougall), Pacific SecliOIl Soc. eCOIl. Pall'olll. Mh,U., Los Allgeles, 559- 573. NILSEN, T . H . & CLJ.RKE, S.H ., Jr. (1 975) Sedimentation and tectonics in the ear ly Tertiary continental borderland of Central California. Prof Pap. u.s. geol. Sun. 925, 56 pp. NORRIS, R.J ., C ... RTER, R .M . & TURNaULL, I.M. (1 978) Cainozoic sedimentation in basins adjacent to a major continental transform boundary in southern New Zealand. J . grol. Soc. Lolld. 135, 191 - 205. PELLO, J . & CoRR ... LES, I. (1971) Characteristics of the sedimentation of early Westphalian D rocks near the north-western border of the Central Asturian coalfield (Cordillera Cantlibrica). Trab . Geol. Ol'irdo, 4, 365-372. R EAI)ING, H .G. (1970) Sedimentation in the Upper Carboniferous of the sout hern flanks of the cen tral Cantabrian Mounlains, Pr~. Geel. Ass. 81, 1-41. READING, H .G . ( 1975) Strike-slip fault systems: an ancient example from the Cantabrians. IXlh lilt. COIlSr. Sedilll. Nice 1975, Theme 4, 287-292. RIDlNO, R . (1974) Model of the Hercynian fold belt. Earth plallet. ScL Leu. 24, 125- 135. RI ES. A.C. (1978) The opening o f the Bay of Biscay-a review. &rth Sci. Rev. 14, 35-63. RI ES, A.C. (1979) Variscan metamorph ism a nd K ·Ar dates in the Variscan fold belt ofS Brittany and NW Spain. J . 8001. Soc. Lolld. 136,89-103. R UPKE, J. (1%5) T he Esla Nappe, Cantabrian Mou nt ains (S pain). Leidse geol. Meded. 32, 1- 74.

HerCYlliall to lare Hercyniall co"tinental strike-slip system

125

RUPKE, N.A. (1977) Growth of an ancient deep-sea fan. J. Grol. 85, 725- 744. SAVAGE, J.F. (1967) Tectonic analysis of Lechada and Curavacas synclines, Yuso basin, Le6n, NW Spain. uid~ gtol. Mnkd.39, 193-247. SAVAGE, J.F. (1979) The Hcrcynian orogen y in the Cantabrian Mountains, N Spain. Kr)"sIiI{inilwm. 14, 91- 108. ScHWAB, F.L. (1976) Modern an d ancient sedimentary basins: comparative accumu lat ion rates. Crology, 4, 723- 727. SJERP, N. ( 1966) The geology of the San Isidro-Porma area (Cantabrian Mountains, Spain). uidst' geol. Me(le(l. 39, 55-128. STAALDUtNEN, C.J. VAN (1973) Geology of the area between the Luna and Torlo rivers, southern Cantabrian Mountains, NW Spain. LeMsl! Ceol. Meded. 49, 167- 205. STEEL, R .J. (1976) Devonian basins of western Norway-sedimentary respo nse to tectonism an d to varying tectonic context. Teclollophysics, 36, 207-224. STEEL, R.J. & AASHEIM, S. M. (1978) Alluvial sand deposition in a rapidly su bsiding basin (Devonian, Norway). In : Flu~ial SedilllC'l/fology (Ed. by A. D. Miall). M elli. Call. Sm:. P/'Irol. Ceol. 5, 385- 4 12. SWIfT, D.J .I'. (1968) Coastal erosion an d tra nsgressive stratigraphy. J. Ceol. 76, 445-456. TANNER . W.F. (1976) Tectonically significant pebble types: sheared, pocked and second-cydeexamples. Seilimelll. Ceol. 16,69- 83. VEEN, J . VAN (1965) The tectonic and stratigraphic history of the Cardano area, Cantabrian Moun tains. northwest Spain. uidsl! gl!ol. Me(Il'(I. 35, 45- 104. WAGNE R, R.H . (1966) Palaeobotanical dating of Upper Carboniferous foldi ng phases in NW Spain. M elll./lIs/.gl!ol. mill. Espmia, 66, 1-169. WAGNER, R.H. (1970) An outline of the Carboniferous stra tigraphy of Northwest Spain. COIWr. Coif. U"iv. Litgt, 55, 429-463. WAGNER, R.H. (l97Ia). The stratigraphy and structure of the Cinera-Matallana coalfield (prov. Le6n, N,W, Spain), Trab. Ceol. O"il!oo, 4, 385-429. WAGNER, R. H. (1971b) Carboniferous nappe si ruclllres in north-eastern Palencia (Spai n). Trab . Geol. O"ltdo, 4, 431-459. WAGNER, R.H. & WAGNER·GENTIS, C. H.T . (1963) Summary of the stratigraphy of Upper Palaeozoic rocks in NE Palencia, Spain. Proc. KOll . Nederl. Akad. Wt S/ellSe/,. Ams/erdam, (8) 66, 149- 163. WAGNER, R.H. & WI NKLER PRINS, C.F. (1970) The stra tigraphic succession, flora an d fau na of Cantabrian and Stephanian A rocks at Barruelo (prov. Palencia), NW Spain. COlwr. Call. Ulli~. LUge, 55, 487- 5S I. WAGNER, R. H. & FERNANDEZ-GARCIA, L. (1 971) The Lower Carboniferous and Nam urian rocks north of La Robia (Loon). Trab. Ceol. Oviedo, 4, 507- 531 . WAGNE R, R.H . & MART INEZ·G ARCIA, E. (1974) The relationship between geosynclinal folding phases and foreland move mentS in North·west Spain. S/ud. Ceol. vii, 131 - 158. WAGNER, R.H., WI NKLF.R PRtNS, C.F. & RIDI NG, R.R. (1971) Li thostra tigraphic units of the lower part of the Carboniferous in northern Le6 n, Spain. Trab. Geol. Ovie(lo, 4, 603- 663. WAGNER, R.H., PARK, R.K. , WI NKLER PRINS, C. F. & Lvs, M. (1977) The post-Leonian basin in Pa lencia: a report on the stratotype of the Cantabrian Stage. In: S)"IuposiJIIIJ on Cllrbol/ijef(!IIs Straligraphy (Ed. by V. M. Holub & R . H. Wagner), Spec. Pub. geol. S,lrv. Prague, 89- 146. WEBQ, G .W. (1 969) Paleoz:oic wrench faults in Canadian Ap palach iQns. In: North A/lalllieCeology ol/d COllfillell/(/I Drill (Ed. by M. Kay). Mem. Am. Ass. PN'ol. Gl!ol. 12,7S4- 786. YOU NG, R. (1976) Sedim/!lIIological s/udits in Ihe Upper Carbol/i/erolls 0/ ,1Or/h·It·esf Sp(ll'" 111111 Pembrokesliif? Unpublished D. Phil. Thesis, University of Oxford .

Spec. Publ. into Ass. Sediment. (1980) 4, 127- 145

Strike-slip related sedimentation in the Antalya Complex, SW Turkey

A. H. F. ROBERTSON and N. H. WOODCOC K Grallt Institute of Geology, West MaillS Road, Edinbllrgh EH9 3JW alld Department of Geology, Dowlling Street, Cambri(lge CB2 3EQ

AB STR ACT A varie ty of mostly ophiolite-
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134

A. fl . F. RobertSOIl alld N. H. Woodcock

Localities A, B; minor breccia wedges Small wedges of stratified ophiolitic breccias occur at several localities ncar the GOdene Zone- Kum luca Zone con tact . In o ne case (Locality A, Figs 2 and 3) Iypical pillowed lavas with interca lated calca reous and siliceous pelagic sed iments become increasi ngly sheared and brecciated upsection , then pass into oligomic! tecto nic breccia composed of angular clasts of crushed radiolarite and pelagic calci lutite in a sheared fr iable lava matrix. Overlying compositio na lly sim ilar breccias show sedimentary fabri cs. Clasts up to 0·25 m in diameter are supported in a matrix of silt and sandsized derived radiolarian chert. The breccias show a tendency to fi ne upwards; clasts are uniformly angula r and poorl y sorted. Some ind ivid ual beds are virtua lly mono miet . Numerous wedges of coarser-grained breccias also cro p o ut towards the Kum luca Zone contact in the NW of the area ( Locality B, Fig. 2). There, clasts up to 1·5 m in diameter of mafic lavas with subordinate diabase, gabbro, serpentinite and pelagic sedimentary rocks occur in a matrix of structureless volcaniclastic si lt. Most of these breccias a re strongly shea red, but a crude sed imentary fabric is st ill visible in most cases. Clast type is normally closely related to adjacent rocks (cf. below). Locality C; ophiolitic rudites resting on sheared ophio lite

Much more extensive developments of mostly ophiolitic clastics were identified by Yilmaz (1978) ncar Cmarclk , N of G Odene (Fig. 2). Mapping of the type area (Fig. 6) reveals up to 70 m th ick seq uences of poorly consolidated undeformed ophiolitic rudi tes which are crudely stratified and o nly gently to moderately incli ned. The sediments range from massive and crudely bedded matrix-supported rudites (units 1- 2 m thick), to laminated ophiolitic arenites sho wi ng traces of grading. Clasts in the

Fig. 4. Positive print of a thin section of the Cmarclk breccias, Localit y C. Note the highly angular, poorly sorted ophiolitic clasts including fresh and altered mafic lava, alten::d gabbro, radiolaria n siltstone and sheared chert. See text for add itional explanation.

135

Strike-slip sedimel1lation ill the Anralya Complex

rudites reach 0·4 m in diameter and locally show weakly developed imbrication (Fig. 7). They comprise lithologies from the whole igneous suite and its former sedimentary cover, including serpentinite, variably serpentinized ultramafics, gabbro, diabase, mafic lava, radiolarian chert, pelagic limestone and rare quartzose sandstone (Fig, 7),

T he predominantly ophiolitic rudiles show interstralification of horizons grading from ophiolitic rudites with only scattered limestone clasts (Fig. 7) to almost pure limestone breccias (Fig. 3). T hese breccias, which are generally more lithified than their ophiolitic counterparts, are composed of clasts of calcarenite and calcilutite

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136

A. H . F. Rober/son lind N. H. Woodcock

litho logica lly comparable to the Tekcdag Massi f, now located several kilometres to the cast beyond a major N- S trending sheet of serpentinite (Fig. 6). In thin section (Fig. 4) the finer ophiolitic rudites consist of clasts of all the ophio litic and sedimentary rocks as well as grains of polycrystall ine quartz presumably derived from turbiditic sandstones intercalated wi thin the mafic lavas. Scattered gra ins of sheared radiolarite, siltstone, Java and gabbro arc abundant. Ferromagnesian mineral s orten show a network affine cracks. Defo rmed grains arc extensively replaced by microspar-sized calcite. Carbonate grains show extensive pressure solution. In contrast, many of the unstrained grains of basalt and gabbro a re surpri singly fresh and un recrystallized. Sheared rocks are represented by grains of recrystallized limesto ne and cleaved chlo ritic siltsto ne. At Cmarclk ( Locality C) the oligomict rudites are seen to rest unconrormably o n steeply inclined sheared and brecciated calcilutites and mafic pillow lavas typical of the GOdene Zone (Fig. 5a). Close to the contact the calcilutites exhibit a marked cleavage o blique to bedding, transitional over several metres into zones of tectonic breccia with sheared a ngula r clasts up to 0·05 m in diameter. Detached blocks of the sheared and brecciated rocks are seen as rafts in the basal ophio litic rudi tes, which are themselves undeformed. The sheared and brecciated limestones are recognizable as late Triassic Halobia limestones originally deposi ted within the lavas. In the surrou nding area the mafic lavas and associated sedimentary rocks are again intensely sheared and extensively brecciated. To the east the exposures arc obliquely trunca ted by a major N- S striking sheet of vertically dipping serpentini te which sepa rates Local ity C from the Tekedag limestone massif and a ssocia ted o phiolitic rudites (Locality E). Locality 0 ; plutonic rock breccias Di stinctive breccias com posed predominantly of gabbroic and ultramafic rocks overlie pi llow lavas and serpentized harzburgite in several areas (Figs 2, 5). Ncar Kirkadinomek Tepe, first described by Yilmaz (1978), medium to mafic gabbros cu t by occasional diabase dykes arc then depositionally overlai n with normal contact by virtually matrix-free clast-supported breccias. These are composed mostly of gabbro bUI with su bordinate volumes of other mafic igneous and sedimentary rocks ( Fi gs 3,5). The relation ship of these breccias to the Cmarclk rudites is unknown. Loca lity E; ophiolitic ruditcs on limestone Ophi oli tic rudites are again found to the NE along the contact of the major TekedaA carbonate massif ( Fig. 2). As depicted in Figs 3 and 5, massive subvertical rccrystall ized Mesozoic limestones ( ?Jurassic) a re unconformably overlain by steeply dipping crudely cross-bedded ophiolitic breccias. At least locally, derivation was from the NE. Rad io larite is particu larly abundant in the basal horizons but surpri singly, in contrast to Locality C, clasts from the stratigraphically underlying limestones are not present. Loca lity f ; ophiolitic rudites and serpcnlinites A va riety of ophiolitic clastics are found intercala ted with serpentinite and gabbro within a ca 8 x 3 km, N- S trending zone located north of the major Baklrh Dag massif (Figs 2, 8). Th is massif, like the Tekedag to the south, originated a s part of a major ca rbo nate build-up within the Gadene Zone and rests in part on pre-rift Permian

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Association of Sedimentologists

148

K. B. Spiirli

Furtherm ore, plale boundary processes have played an important role during its entire geological history, which can be traced back to the latc Precambrian. The present paper reviews knowledge about the development of the New Zealand continent, with specia l emphasis on the relative movements of adjacent plates in the New Zealand region and the effect of these movements on the pattern of Cainozoic faul ts and sedimentary basins.

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New Zealond ond obliqlle-slip margins

149

The Alpine Fault is a major tectonic feature of New Zealand (Wellman, 1955 ; Suggate, 1963). It has a dextral displacement of at least 480 km . The displacement may be as large as 1300 km if the sigmoidal bend ing of New Zealand ( Fig. I) is also taken into account (Well man, I974). The age of the Al pine Fault is still under dispute. Some authors (Ballance, 1976 ; Carter & Norris, 1976) set its initiation in the Tertia ry; others (Suggatc, 1972 ; Grindley, 1974) prefer a Cretaceous age. H"owever, the sigmoidal bending of New Zealand, which ind icates a regime of predominantly ducti le shear, most likely occurred in ea rly Cretaceous time ( Rangitata Orogeny, see below) when plutonic processes ( Landis & Coombs, 1967; Aronson, 1968) may have ' softened up' the continental margin. It is possible that the Alpine Fault may have ori ginated by reactivation of a pre-existing Palaeozoic fault , o f the type described by Harri ngton, Burn s & Thom pson ( 1973) and Cooper (197 5) .

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A second, large dextral fau lt may lie j ust east of the Sou lh Island along the western margin of the Campbell Platea u (Cullen, 1970 ; Christoffel, 1978; Fig. 2, this paper). It causes an offset of the Stokes Magnetic Anomaly (Wellman, 1973 ; Hatherton. 1975). Th ree major orogenies have been recognized in New Zealand; (i) the Devonian to Carboniferous Tuhua Orogeny, (ii) the early Cretaceous Rangitata Orogeny a nd (ii i) the now active Kaikoura orogeny, which commenced in mid Tertia ry time. Up to the end of the Rangitata Orogeny the geologica l history of New Zealand was that of the margin of Gondwanaland (Craddock, 1975 ; Fig. I, this paper). After the Rangit31a Orogeny New Zeala nd separated from Gondwanaland and eventually became part orthe boundary between the Indian and Pacific Plates.

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The northern branches of the Alpine Fault (Wairau, Awatere, Clarence and Hope faults) define a field of dominantly northeast-trending structure associated with dextral st ri ke slip (e.g. Lensen, 1968 ; Freund, 1971). Microseismic studies indicate that this field may be slowly propagating towards the south (R ynn & Scholz, 1978). Elsewhere an oblique rhombic pattern prevails, except in the 'basin and range' province of eastern Otago (Fig. 5) where the pattern is rectangular. T rends similar to those of the rectangular pattern arc also present in the subsurface of the Canterbury Plains ( D. Wilson, N.Z. Geological Survey, Christchurch, personal communication) and in the Chatham Ri se to the east (Austin, Sprigg & Braithwaite, 1973). At present most of the NNE and northeast-trending faults in the South Island have reverse components of movement. Because of this, there are folds parallel to both fault direct ions, giving rise to complex non-cylindrical interference structures in some of the Cainozoic basins (Bradshaw, 1975). Reactivation of Cretaceous faults, followed by reversal of the sense of movement has been recorded from a number of localities (Bishop, 1974, p. 331). Usually the change is from a normal to a reverse component of movement. It commonly can be timed to have to have taken place during the Late Miocene (Carter & Norris, 1976). Prominent master shear zones of the South Island besides the Alpine Fault and its branches are the Paparoa Tectonic Zone (Laird, 1968, 1972), the Moonlight Tectonic Zone (Norris ef al., 1978) and the yet little known Shag River Fault zone (Fig. 5). All of these faults have histories of movement dating back to the Cretaceous and, in the case of the Paparoa Tectonic Zone, possibly earlier. The Moonlight Tectonic Zone may be the compressed on land continuation of the Oligocene Emerald-Solander trough (Fig. 2) (Norris & Carter, 1980). North Island (Figs 6 and 7a) The influence of the Alpine Fault becomes diffuse in the North Island and the fault pattern is more complex than in the South Island . The zone of most intense Cainozoic deformation lies along the east coast (East Coast Deformed Belt). Together with the adjacent Hikurangi trough ( Katz, 1974a; Eade & Carter, 1975) it represents the surface expression of subduction under the North Island ( Lewis, 1980) outlined by earthquake foci (Adams & Ware, 1977). From east of Wellington almost to Hawke Bay the structure is dominated by thrusts dipping away from the Hikurangi Trough, the thrusts becoming steeper landwards and changing into strike-slip faults adjacent to the axial ranges (Lewis, 1980). Actively growing anticlines are known on the coast and continental shelf of Hawke Bay (Lewis, 1971) and on the coast to the south (Ghani, 1978). Some distinct, northsouth trending en echelon structures, basement cored in the south, but only affecting younger strata in the north, can be recognized within the belt (Kingma , 1967 ; Fig. 6. Cainozoic fault pattern, North Island . Compiled after Adams & Ware (1977), Ballance & SpOrli (1979), Davey (1974, [977). Grindley ([960), Hay (1967), Healy el al. (t964), Katz (l974a, b), Kea r ([960), Kear & Hay (196[), Kingma (1962, 1964, 1966, 1967), Lensen et af. (1959), Lewis (1971), Pilaar & Wakefield (1978), Ridd (1964), Schofield (1967), Speden (1976), Stonely ( 1968), Thompson (1961). Open arrow indicates direction of present day plate convergence. Shaded: uplifted axial basement ranges. Faults with both teeth and hachure are normal faults reactivated by reverse movement. ED : East Coast Deformed Belt. M: thrust locality. Mathesons Bay, North Auckland. WF : Waikato Fault. E: Mount Egmont. TPH: Tongapurutu-Patea High. HA: Hauhungaroa Block. T: Tongariro Volcanoes. WM: Wanganui Monocline. H BM: Hawke's Bay Monocline.

158

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b.

Fig. 7. (a) Late Quaternary faults, North Island, afte r Lensen (1977). (b) New Zealand domains of Cainozoic structure. showing rhombic and rectangular rault palterns, thrust zonts (toothed lines). major folds, monoclines (strike and dip symbols) and rifts (li nes wit h hachures).

Johnston, 1975; Fig. 6, this paper). The orientation of these oblique fol ds is consistent wi th dextral st ri ke-slip along the northeast direction. Unconformities show that cha nges fro m thrust imbrication on northeast-striking fau lts to ell echelon fold ing on northsouth trending axes have laken place, while imbrication has persisted in adjacent belts. Thus a n alternat ion between complete decollement of the sed imentary sequence a nd morc 'a utochthonous' en echelon folding, directly recording the obl ique-slip vector, is indicated. The East Coast Deformed Belt is bounded in the west by the uplifted, ax ial greywac ke ranges (Figs 6, 8). For about 200 km northeast of Wellington they form a narrow block bounded both in the cast and the west by steep reverse fa ults (Kingma, 1962, 1967). Oblique, very open fold s and warps aga in indicate that the strain during uplift incl uded dext ral shear along northeast trendin g fa ults ( Fi g. 8). Nea r the centre of the North Island, the zone of upl ifted basement blocks widens a nd instead of being thrust-bound in the east it adjoi ns the act ively lilti ng Ha wkes Bay Monocline (Fig. 6). Fa ults al the northern end of t he axial ranges originated in the Cretaceous and have experienced reversal of movement ( Moore, 1978). A swing into a north-south trend of the tectonic grain corresponds to the sigmoida l bend on the west side of t he North Isla nd . North of Hawkes Bay a nd east of the a xial ra nges, the structural pattern is strongly influenced by northwest lrends. Some of lhese a re inheri ted from a phase of southward thrusting or gravi ty sliding in the Late Oligocene ( Ridd, 1964 ; Stonely, 1968 ; Speden, 1976) which involved em placement of the Matakoa oph iolites ( Brothen;, 1974). From the Bay of Plenty to the centre of the North Isla nd, the Taupo Volcanic Zone (Cole, 1978) lies 10 the west of the uplifted a xial ranges. It coi ncides with a rift-l ike

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S()urc(>s. (Ed , by M, T. Halbouty, J . C. Maher & H . M . Uan). Am. Assoc. Pelral. G(>()I. Mem. 25, 217-288. KEAR, D. ( 1960) Sheet 4 Hamilton ( 1st cdn). Geological Map o/New Zea/alld I : 250000. D .S. I. R. Welli ngton, N, Z. KEAR, D . ( 1964) Volcanic alignments no rth and weSt of New Zealand's central volcanic region . N .Z . J . G(>ol. Geophys. 7, 24-44. KE.... R, D . & HAY. R .F, ( 196 1) Sheet 1 Nonh Cape. GeologiclI/ Mllp 0/ NI'''' Zelllmld I : 250 000. D.S. I. R. We lli ngton, N .Z. K ENNETT, J .P. (1 971) Cenozoic e yolution of A nta rctic glacia tion, the C ircum-Antarc tic Ocean and their impact on global paleooceanography. J. geoph. Res. 82, 3843- 3860. K1NG M.... , J.T . (1962) Sheet 11 Dannevirke (1 s t edn). G(>ologiral Map 0/ New Zl'alalld I : 250 000. D .S.I. R. Wellington. N.Z.

168

K. B. SpOrli

KI NG"''', J.T . (1964) Sheet 9 Gisborne ( lst cdn). GrolQgi("fl' Map (IfNI'''' Zl'aland J : 250 000. D.S.I.R. Wellington, N.Z. KlNGMA, J.T. ( \ 966) Sheet 6 East Cape ( 1st cd.,) Gt!ofogiraf Map of New Zealand I : 250000 D.S. I.R. Well ingto n, N.Z. KING MA, J.T . (1967) Sheet 12 Wellington ( 1st edn). Geological Map 0/ New Zeo/(//I(I 1 : 250000. D .S.L R . We ll ington, N.Z. KINGMA. J.T . (1971) Geology of lhe Te Aute Subdivision. 81111. N.Z. Grol. Slirv. 70, l 73pp. LAIRD, M .G. ( 1968) T he Papa roa Tecton ic Zone. N.Z. J . Gro'. GNJph)'s . I I, 435-4S4. LAIRD. M.G. ( 1972) Sedimentology of the G reenla nd Grou p in the Paparoa Ra nge, West Coast. South Island. N .Z . J. Grol. Gl'Oph. IS, 372- 393. LANDIS. C .A. & COOMIlS. O .S. (1%7) Metamorphic belts a nd o rogenesis in southern New Zealand. T«IOIIOpl",sics, 4, SOI- 518. LENSEN, G. J. (J962) Sheet 16 K aikoura (1st edn), Grologicol MlIp ofNe ... Zeolalld I : 250,000. D .S .I.R . Wellington, N .Z. LENsEN, G .J . (1968) Analysis of progressive fault displacemcnt during downcuUi ng at the Branch R iver lerraces, South Island, New Zea land. 8u/l, gl'ol, Soc . Am. 79, 545- 566. LENs(N, G.1. ( 1915) Earth deformation stu d ies in New Zeala nd. Teclollophysics. 29, 54 1- 55 1. LENSEN, GJ. (1917) Late Quaternary tectonic map of New Zealand I : 2000000 (1st cdn). N.Z. Geol. Slirv. /lUsc. S eries Map 12. D .S. I.R . Welliniton, N.Z. LENSEN, G .J ., FLa.tING, C.A. & KI NGMA, J.T. (1959) Sheet 10 Wanganui (1st cdn). Geological Map of Ntw Zealalld I : 250000. D.S.I .R . Wellington, N .Z. LE P ICHON, X. ( 1968) Seafloor spreading and continental drift. J . geophys. Res. 73, 3661- 3697. LESLIE, W.C. & HOLLI NGSWORTH. R.J.S. (1972) Exploration in the East Coast Basin, New Zealand. A/lSI. Pelrol. Expl. Au. J. 12, 39-44. LEWIS, K .B. (1971) Growth rate of folds using tilted wave-planed surfaces: coast and continental shelf, Hawkes Bay, New Zealand. In: R('celll Crllslal M o,·t/l/('lIIs (Ed. by B. W. Colli ns & R . Frazer). R. Soc. N,Z. 811/1, 9, 225- 231. LEWIS. K .B. (1913) Erosion and depos iti on o n a tilt ing con tinental she lf d uri ng Quaterna ry oscillations of sea leve1. N.Z. J. GMI. Grophys. 16, 28 1- 301 . LEWIS, K .B. ( 1980) Quaternary sedimentatio n in the H ikurangi oblique subduction and transform margin, New Zea land . In : S l'dimell/atiOIi ill oblique-slip m obile ;:O/les (Ed. by P. F. Ballance & H . G . Reading). Spec. Pub!. illl. AS.!'. Sedim('III. , 4,171 - 189. LILLIE, A.R. ( 1953) The Geology of the Dannervirke Subdivision. BIIII. N.Z. Geological Survey 46, 152 p. LiNGEN, G .J. VAN DER & P£ITINGA, J.R. ( 1980) M iocene slo pe-basi n sedimentation along the New Zealand sector of the Aus tral ian- Pacific convergent plate bou ndary. In: S ..dimellla/;Ol/ ;f! obliqueslip mobile ;:OlltS (Ed. by P. F. Ballance & H . G . Reading). Sptr. Pllbl. illl. A ss. Snlimelll. 4, 19 1-2 15. Mc K ELLAR. LC . ( 1966) Sheet 25 D unedin. Geologirol /I1tlP of Nth' Zi-alolld I : 250000. D .S.L R . Welli ngton, N.Z. MOLNAR, P., ATWATER. T ., MAMM ER IC" X, J . & SMITH, S. M . ( 1975) Mag ne tic anoma lies, bathymet ry and tectonic evolution or Ihe So uth Pacific since the La te Cretaceous. Geopliys. J. R . A str. Sor. 60, 383-420. MOORE, P.R. (1978) Geo logy of western Koranga Valley, Raukumara Penin sula . N.Z. J. Geol. Gtopl,ys. 21, 1- 20. MUTCH, A.R. (1963) Sheet 23 Oamaru ( 1st ed n). Geolog ical Map of New Zealand I : 250 000. D .S.I .R . Wellington, N .Z . MUTCH, A .R. & MCKELL\R, I.C. ( 1964) Sheet 19 Haas t ( 1st cdn). Gt%gical Map of N ew Zenlmlll I : 250 000. D's.I. R . Wellington, N,Z. NATHAN, S. ( 1974) Stra tigra phic nomenclature for the Cretaceous-Lower Quaternary rocks of Buller an d North Wes tland, Wes t Coast, South Island, N ew Zeala nd. N .Z. J. G('ol. Geopliys. 17,423-445. NATHAN, S. ( 1977) Cretaceous and Lo wer Tertiary stralillraph y of the coastal strip be tween Butt ress Point and Ship Creek, So uth West la nd, New Zea land, N .Z . J. Geol. Gtop!'ys. 20, 615- 654. N ATHAN, S. ( 1978) Upper Cenozoic s tra tigraphy of South West land, New Zealand. N.Z. J. Geol. Geophys. 21, 329- 36 1. NEALL, V.E. ( 1974) TIl .. VoJ"all;r h;storyofToratwki. Egmont N a tional Park Board, 14 pp.

Nell' Zealmul aI/(/ oblique-slip margins

169

NEEF, G. ( 1974) Sheet N 153 Eketahuna ( 1st cdn). Grologiral Map of NI'li' Zl'(Jllmd I : 63 360 D.S.I.R. Wellington, N.Z. NElSON, C.S. ( 196S) Sedimentology of redeposited calcareous and glauconitic beds at Pa haoa , sou th -east Wellington. Trmu. R. Soc. N.Z. 6, 45-62. NElSON, G.S. &. Hu,," ;. T .M . ( 1977) Rela tive intensity of tectonic events revealed by the Tertiary sedimentary record in the North Wanganui Basin and adjacent areas. New Zealand. N .Z . J. GNJI. Geophys. 20, 369- 392. NORRIS, R.J. ( 1979) A geometrical study oftinite strain an d bending in the South Island. In : Origin of the SOllllle1ll Alps (Ed. by R. I. Walcott & M. M. Cresswell) Roy. Soc. N.Z. Bull. IS. 21 - 2S. NORRIS, R.J., C",RTEM , R.M. & TUR NBULL. I.M. ( 1978) Cainozoic sedimentation in basi ns adjacent to a major continental boundary in southern New Zealand. J. gl'ol. Soc. /..oml. 135, 191 - 205. NORRIS. R.J. & C ... RTER. R.M. ( 1980) Offshore sedimentary basins at the southern end of the Alpine Fault. New Zealand. In: Sl'tfilllelltatioll ill oblique-slip mobile lQlleS (Ed. by P. F. Ballance & H. G. Reading). Spec. Publ. int. Ass. Sedimellf., 4, 237- 265. OnDRN. L.E. ( 1959) Sheet 21 Ch ri stchUl'(:h ( 1st edn). Geological Map of Nl'w Zealand 1 : 250000. D.S. I.R. Wellington, N.Z. O'BRIE N, J.P. & ROOGERS, K.A. ( 1973) Alpine-type serpentinites from the Auckland Province-I. The Waircre Serpentinite. J. R. Soc. N.Z. 3, 169-190. r"'CI(II M,1, G. H. & ANDREWS, J .E. ( 1975) Results of Leg 30 and the geologic history of the sou th west Pacific arc and marginal sea complex. I.n: Illilial Rl'ports of Deep Sea Drilling Proferl (Ed . by J. E. Andrews & G. H. Packham el 01.), 30, 691-705. Washington D.C. P... CKH ... M, G. H. & TERRILL. A. ( 1975) Submarine Geology of the Soulh Fiji Basin. In : Initial Reports oflhe Deep Sea Drilfillg Prajerl (Ed. by J .E. Andrews & G . H . Packham 1'1 01.), 30, 617-633. Washington D.C. PtL4. ... R. W. F.H. & W",I(EftELD, L.L. (197S) Structural and stratigraphic evolution of the Taranaki Basin. offshore New Zealand. APEA J. 1975. 93- 102. PREBBLE. W. ( 1980) Late Cainozoic sedimentation and ta.:tonics of the East Coast Deformed Belt in Marlborough, New Zealand. In: Sedimel/totioll in obliqlle-slip mobile zones (Ed . by P.F. Ballance & H. G . Readi ng) Spec. Publ. jill. Ass. Sed;mellt. 4 , 217- 228. RtDD, M. F. ( 1964) Succession and stroclUral interpretation of the Whangara-Waimate area. N.Z . J. Gtol. Geophys. 7, 279- 298. ROBtNSON, R., C ... LII ... EM, I.M . & THOMSON, A.A. (1976) The Opunake, New Zealand earthquake of 5 Nov. 1974. N.Z. J. GNJI. GNJphys. 19, 335-345. RYNN, J .M.W. & SCIiOLZ. G. H. ( 197S) Seismotectonics of Arthur's Pass re8ion, South Island. New Zealand. Geo/. Soc. Am. Bllfl. 89, 1373- 1388. SCHOFtELD. J .e. ( 1967) Sheet 3 Auckland (1st cdn) GNJ/agicol Map 0/ New Zeolllllli 1 : 250000' D.S. I.R. Wellington, N.Z. SCUTER, J.G., J.W. Jr, M... MMERtCI(X, J . & CH ...S£, C. G . ( 1972) Crustal ex tension between the Tonga and Lau Ridges: Petrologic nnd geophysical evidence. Buff. geol. Sor t Alii. 83, 50S- SIS. SPEDEN, I.G. (1976) Geology of MI. Taitai, Tapuaeroa Valley. Raukumara Peninsula . N.Z. J. GeQI. Ceop/I. 19, 7 1- 11 9. SPORLt, K.B. (197S) Mesozoic tectonics, North Isla nd, New Zealand. Geol. Soc. Am. B/llf. 89,4 15-42S, STEYENS, G .R. (1974) RlIgged wlIllsrape, Ihe Geology 0/ Celllral New Zea/(IIIII, 2S6 pp. A. H. & A. W. Reed, Wellington. STONELEY, R. ( 1968) A Lowe r Tertiary decollemcnt on the east coast, North Island, New Zealand. N.Z. J . Geol. Cl'Ophys. 11 , 128-156. SUGG ... n;, R.P. (1963) The Alpine Fault. TrollS. R. Soc. N.Z. 2, 105- 129. SUGGUE, R.P. ( 1972) Mesozoic-Cenozoic development of the New Zealand region. Pacifir GtOlogy, 4, 113- 120. TE PUNG.... M.T. (1957) Live anticlines in western Wellington. N.Z. J. Sdenu ond Tl'dllwlogy, 388 , 433-436. THOMPSON, B.N. ( 1961) Sheet 2A Whangarei. GNJlogirol Mop 0/ Nt'" Zealalld I : 2SO 000 D.S. I.R. Wellington, N .Z. W"'LCOlT, R.1. (1978a) Present ta.:tonics and Late Cenozoic evolution of New Zealand. Geopllys. J . R. ostr. Soc. 51, 137- 164. W"'LCOlT, R.I. ( 1978b) Geodetic strains and large earthquakes in the Ax ial Tectonic Belt, of North Island. New Zealand. J . grophys. Res., 83, 4419--4429.

170

K. 8. Sporli

WAlUU!N. G . ( 1967) Sheet 11 Hokitika ( 1st 000), Groiogical Map o/Nrll' Zroloml I : 250000. D .S. I. R. Wellington, N.Z. WATTERS, W .A ., SPEOEN, LG. & Wooo, B.L. (I968) Sheet 26 Stewa rt Isla nd (1st cdn). GNJ/ogiral M(lpofNr"'Z~/and 1 : 250000. D.S. LR. Wellington, N.Z. WATTS, A.D.. WElmL, J.K. & DAVt:Y, F.J. ( 1977) Tectonic evohuion of the South Fiji ma rginal basin. In: l :slol/d Arcs, Df!f'p Sea TUlldleyand Bock Arc Basins (Ed . by M. Talwani & W. C.

Pitma n Ill). Am. Ceophys. Ul/iOl/, MOl/rice £y";ng Sf", 1,419-427. WEISSEL. J .K . (1977) Evolution of the Lau Basin by the growt h of small plates. In: Island Arc.!", Dup Sf'O Trt'lIcheSQI/{/Back Arc Basil/s(Ed . by M . Talwani & W. C. Pi tman III), Am. Grophys. Unioll MOl/riu E.... i,lg Sf'r. 1,429-436. WEISSE"', J. K .• H AYES, D.E. & HERRON, E.M. ( 1971) Plate tectonic symhesis: the displacements between Australia, New Zealand and Antarctica since the Late Cretaceous. Mar. Grol. 25, 231- 277. WELLM,\N N, H .W. ( 1955) New Zealand Quaternary tectonics. Geol. RlllldJ·cJlIlII. 43, 248- 257. WELLM,\N, H.W. ( 1973) The Stokes Magnetic Anomaly. Geol. Mag. 11 0,419-429. WELLM,\N, H.W. (1 974) Recent crustal movements in New Zealand. TeclollophY$ic$, 23, 423-424. WELLM,\N, I'. & COOPER, A. ( 1971) Pota ssium argon age of some New Zea lan d lamprophyre dikes near the Alpine Faull. N. Z. J. Ceol. Geoph. 14, 34 1- 350. WI LSON, D.O. (1953) The geology of the Wa ipara subdivision. N.Z. Geol. Sliney BII/{. 64, 122pp. WOOD, B.L. (1960) Sheet 27 Fiord (1st edn). Geological Map of Nt'''' Zt'a!(//u/l : 250000. D.S. I.R . Wellington, N.l. WOOD, B.L. ( 1962) Sheet 22 Wakatipu (1st edn). Gt'Ologiral MapofNe", Zealand I : 250000. O .s. I.R . Wellington, N.Z. WOOl), B.L. (1966) Sheet 24 Invercargill ( 1st cdn). Geological Mop of Ne'" ZealDlld I : 250000. D.S.I. R. Wellington, N.Z. WRIGHT, A.C. &. B,-",cK, P.M. (1979) Geochemistry and petrology of the Waitakere Group, North Auckland, New Zealand. 49th ANZAA S Congre$$, Auckland, Abstracts 1,18 1.

Spec. Publ. illsl. Ass. Sediment. (1980) 4,171-189

Quaternary sedimentation on the Hikurangi obliquesubduction and transform margin, New Zealand

K. B. LEWI S

Nell' Zealalld Oceanographic Ills/illl/e, Wellington North, New Zealand

ABSTRA C T The Hikurangi Margin{frough system on the northeastern side of New Zealand is mainly an extension of the Tonga- Kemladec Arc{Trench subd uction system into a conlillCnlal environment. Structural elements become progressively more elevated and subduction progressively more oblique towards the south until the whole system is truncated at a strike-slip, transform boundary that extends along the sout hwestern part of the Hikurangi Trough and the Hope Fault to the Alpine Fault. Subduetion, eombined with rapid detrital sedimentation, has led to the development of a ISO km wide, imbricate-thrust controlled, accretionary borderland of seaward·faulted, anticlinal ridges and landward-tilting basins. The basins are generally 5- 30 km wide, 10-60 km long and contain fill 200-2000 m thick. The borderland continues on land where the highest accretionary ridges (normally at mid-bathyal depths) form a line of coastal hills in front of a line of strike-slip faulted, highest accretionary basins and volcano-backed, frontal ranges. Turbidites, hemipelagic muds and volcanic ash layers fill the tilting slope basins with wedge-shaped layers. at rates ranging from about 0·1 m/](K)() years in lower slope: basins to about O· 3 m/ IOOO years in upper slope: basins. Prisms of sandy mud build the shelf upwards at maximum rales of 3·0 m/ IOOO years during interglacial periods of high sea level, and the upper slope upwards and outwards at similar rates during glacially lowered sea level. On the upper slope, sheets of sediment more than 10 km in length but only a few tens of metres thick have slumped on slopes of as little as ] 0, probably after dewatering of surface mud has trapped excess pore water in underlying coarse silty layers. Along the steep, southwestern transform margin much of the influx of muddy sediment is fed direct to the Hikurangi Trough along canyons.

I N TROD UCTIO N The plate boundary through New Zealand Quaternary sed imentation in New Zealand is dominated by its position across the boundary between the Indian and the Pacific Plates. A plate boundary has passed through t he conti nen tal mass or New Zealand ror the last 40 m.y. , with the Indian 014 I -3600/80/0904-0 171 $02.00

1980 International Association of Sedimentologists

172

K. B. Lewis

Plate moving more rapid ly northwards away from the spreadi ng Pacific-Antarctic Ridge than the Pacific Plale ( Mol nar el 01. , 1975). The two plales have sheared some 1000 km past one another, the relative motion having been taken up by fault move· ments and by rock deformation. However, the movement has rarely been simple shear. Various cha nges in the configuration of the boundary and of the spreadi ng centre have meant that , from lime to time and from place to place, relative moti on has been either oblique extension ('transten sion') or oblique compression (,transpression') (Carter & Norris, 1976 ; Ballance, 1976; Sporli , 1980). For the last 10 m.y., the basic movement on most sectors of the boundary has tended more and morc towards oblique compression. Thc compressional element appears to have migrated southwards rrom the Kermadec T rench area and to have increased in intensity about 2- 3 m.y. ago. It was then that the Southern Alps began to rise rapidly towards the cl imax orthe Kaikoura Orogeny (Walcott , 1978a). To the north of New Zealand along the Tonga-Kermadec Margin, it is the Pacific plate that is su bducted. To the south of New Zealand , along pa rts of the MacquariePuysegu r Margin, it is the Ind ian Plate that underrides (Hayes & Talwani, 1972). In each case oceanic crust is subducted beneath oceanic crust (Fig. I). Because or the long con tinued strike-slip movement along the boundary, there are mirror image zones in the northeast and southwest where oceanic crust is subd ucted beneath continental crust. The fl oor or the sou thwest Pacific Basin disappears beneath

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Ag. 1. Major elements of the Indian- Pacific Plate boundary in the New Zealand Region. Stippling represents cOl1linental crust. Arrows show relative motion of Pacific Plate with respect to the Indian Pla te. Lines represellt direction of motion of underth rusting plate (Adapted from Wakoll, 1978a. b).

The Hikurangi oblique sub(llictioll ami trallsform margill

173

the 500 k01 long, eastern side of the North Island and the floo r of the Tasman Basin dives under the Fiordland corner of South Island (Cristoffel & van der Linden, 1972). Along the west coast of South Island the obliquely compressional boundary cuts through cont inenlal crust. Since continental crust is not easily subducted, the edge of the Pacific Plate rides up on to the Ind ian Plate to form the Southern Alps. Some of the motion is taken up by thrusting on the Alpine Fault but much of it takes place over a much wider zone of deformation (Walcott, 1978b). The H ikurangi Trough

In the Cook Strait Area, central New Zealand, the boundary is not so obvious. T he Alpine Faull divides inlo numerous smaller fa ults that con tinue nort hward s into the ranges of North Island. One or several of these fau lts have been regarded as the plate boundary but it is now considered (Walcott 1978b) that the real boundary lies offshore to the cast along the elongate depression known as the Hikurangi Trough, or ' Hikurangi Trench ' ( Brodie & Hatherton, 1958). The feature is only 3 km deep and barely deeper than the seafloor to the east unti l it merges south wards into the V between central New Zealand and the Chatham Rise (Fig. 3). In accepted bathymetric terminology t he feature is a 'trough' (Eade & Carter, 1975). Most authors (Brod ie, 1959 ; Panti n, 1963 ; Houtz el al., 1967 ; Hatherton, 1970 ; Ballance, 1976 ; Walcott, 1978a) have regarded the H"iku rangi Margin as a continuati on of the Kermadec Trench/ Rise compressional system. However, Kat'z ( 1974a), citing a gravity anomaly well to the west of its typical trench position (Hami lton & Gale, 1968) IOgether with some of the profi les presented here, concluded that the whole of the broad trough between eastern North Island and the Chatham Rise is simply a downwarped continental basin. The alternative explanation is that the displaced gravity anomaly coincides with an abrupt increase in steepness of the downgoing plate and the Hikurangi Trough represents the si te of low angle underthrusting (Walcott, 1978b). It is considered here that the Hi kurangi Trough is two separate structures; a northern, sed iment fl ooded, volcanic-knoll studded SSW trending struct ural conti nuation of the Kermadec Trench and a southern, more east-west trendi ng, transform boundary between central New Zealand and the downwarped con tinental crust of the Chatham Rise (Fig. I). The northern boundary is at an acute angle to the direction of relative plate motion (M inster el af., [974) so that Paci fic ocean ic crust is obliquely subducted beneath Nort h Island. The southern boundary is almost para llel with the direction of relative plate mOl ion and is more nearly a si mple, strike-slip transform although Central New Zealand rises up slight ly onto the Chatham Rise crustal block (Bennett, in prep. ). I n fact , relative plate motion is taken up nonuniform ly across a 1- 250 km wide zone of deformation to landward. Much of the strike-slip movement is in the most landward part of the zone so that relative movemen t at the boundary itself may be nearly at right angles to the boundary (Walcott, 1978b). ANA TOMY OF AN OBLIQ U E- SU BD UC TIO N M A RCl N The model

Structural and sed imentary mechanisms on the slopes adjacen t to trenches have been proposed by Kari g & Sharman (1975) and Moore & Karig (1976). St ructural

K. B. Lewis

174 Volcanic Bas;n

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Fig. II . (a) Cross section E- F (Fig. 3a) showing present-day relationship of eastern Makara Basin fiU sequence \0 the WaimaramaM angakuri Coastal H igh. The normal faulting is due 10 relatively recent (Pliocene to present) slumping towards the H ikurangi Trough. (b) Reconstruction of cross section A , showi ng onlap relationship of flysch Siraia against the Waimarama- Mangakurl Coastal High, during deposition of the Ponui Sandstone. T he contemporary origin of the reverse faults is considered probable, but not proven.

The Makara Basin

211

strike for almost the entire length of the basin (Fig. 6) and extends over a slightly larger area than the preceding fl ysch strata, but is nevertheless confined to the western part of the basin. The thinning-upward unit may represent a channelized sequence, bu t other explanations are possible (see Martini & Sagri , 1977). A westward shift of the basin depocentre occurred during the Late Miocene (Figs 5, 7) . This was due to continued thrust movement and uplift of the WaimaramaMangakuri Coastal High and possibly the early development of the Elsthorpe Anticline (Fig. 7). During Upper Tongaporutuan time only massive hemipelagic mudstones accumulated over the eastern part of the basin , wh ile to the west flysch sedimentation continued well into the Upper Tongaporutuan (Fig. 7). During the enti re history of the basin , rhyolitic volcanism was active. Tuff beds, both ash-faJl deposits and layers of ash redeposited by sediment gravi ty flows, are intercalated in the flysch sediments. A substantial component of the flysch sediments themselves consists of volcanic particles. In the Upper Tongaporutuan, towards the top of the basin sequence, rhyolitic volcanism increased, and current-deposited sandstone beds almost exclusively consist of volcanic ash , while the mudstones also have a high ash content (subfacies 4). Intensification of tectonic activity at the close of the Miocene terminated the flysch sedimentation in the Makara Basin and caused an unconformity to develop in the vicinity of the Dtane Anticlinal Complex and the Waimarama- Mangakuri Coaslal High (Fig. 3) . Substantial uplift occurred, and the Te Aute limestone, representing widespread sha llow marine deposition, was deposited during Pliocene time ( Kingma, 1971 ; Pettinga, 1976, 1977, 1980). The Elsthorpe Anticline probably developed fully during the late Pliocene and Pleistocene tim es, a period during which the region was also uplifted above sea level. The coastal district has since been affected by gravitational tectonic gliding manifested onshore by the presence of numerous normal faults with substantial down throws to the east, and westward tilting of large fault-bound blocks (Pettinga, 1980) (Figs 3, 6). Flysch sedimentation continued in other parts of the East Coast Deformed Belt well into the Pli ocene (Fig. 2), and is still active in the present-day offshore area (Lewis, 1980).

SU MMARY AND CONCLUS I ONS

The Miocene Makara Basin in the Hawke' s Bay area is one of a series of Neogene flysch basins which form part of the East Coast Deformed Belt which is situated within the present-day North Island oblique subduction system. The Makara Basin (and the same holds for the other Neogene flysch basins) is thought to have formed on the inner slope of the subduct ion trench ( Hikurangi Trough). It is now uplifted above sea level by imbricate thrust faulting of the leading edge of the upper plate (Fig. 12). The interpretation of the basin as a 'fossil slope basin' is based on comparison with other slope basins described in the literature (Grow, 1973 ; Karig & Sharman , 1975 ; Moore & Karig, 1976 ; Smith , Howell & Ingersoll, 1979), and by analogy to the present-day setting of basins in the inner trench-slope offshore Hawke's Bay ( Lewis & Kohn , 1973; Lewis, 1980). Characteristics of these slope basins and similarities to the Makara Basin are: (I) Size. The now exposed Makara Basin measures 20 by 30 km, which is similar

212

G. J. 1'011 der Lingen and J. R. Perringll Taupo Volcanic Zone Mo~orQ 8Q~ln

QUATERNARY

I ~ IOC EN£ J

.--L

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Fig. 12. Schematic cross section through the North Island Subduction System at the present day. Ages or basins shown where known (onshore). Offshore basins schema]ic.

to present day basi ns of inner-trench slopes elsewhere (e.g. Aleutian, Sunda, Shikoku & Hiku rangi). (2) Pa/aeobarhymelry. Microfaunas from the hemipclagites in the Makara Basin indicate a n outer neri tic 10 bathyal depth of deposition . (3) Bounding highs. The Olane Anticlinal Complex and Waimarama- Mangakuri Coastal High which bound the Makara Basin are narrow linear Ihrust zones, consisting of stro ngly deformed li thologies older than the basin sedimen ts. A simi lar situation is described fo r offshore basins (see Lewis, 1980). These thrust faults dip away from the Hikurangi T ro ugh. (4) Sl'lJimenfS. Derivation of flysch deposits was from up-slope, and of debris flow deposits and slumps from the thrust ridges. Tuff beds in the Makara Basin have analogies in the offshore basi ns, where dateable ash layers deri ved from the Taupo Volcan ic Zone occur (Lewis & Kohn , 1973). (5) Present-lillY bllsi" geometry. The structure of the basin is that of an asymmetric syncl ine, tilting occurring due to progressive growt h and rotation of thrust ridges (imbricati on). During sedimentation this resulted in a la ndward sh ift of the depocentre, and hence asymmetry. The late development of the Eisthorpc Anticline has divided the basin into two syncl ines. The grad ual development of similar ba sins is recogn ized elsewhere ( Moore & Karig, 1976; Lewis, (980). The Austra lian- Pacific plate boundary, of wh ich the North Island Subduction System forms a part, was propagated southwards from the Tonga- Kermadec Subduction System into the New Zealand cont inenta l area in Late Oligocene time ( Ballance, 1976 ; Walcott, 1978a, b ; Sporli , 1980). Although su bduction took place, and is still taking place, o bliquely to the East Coast Defo rmed Belt, no field evidence of strike-slip movements exists in the Hawke's Bay area of the belt. Only compressive folding and thrust faulting are evident. Walcott ( 1978b) suggested that the strike-slip componen t of the oblique subduction is being taken up furthe r to the west, in a zone now occupied by the Axial Ranges, forming the continuation of the South Island Alpine Fault (see a lso Sporli, 1980; Lewis, 1980). Dextra l offset along this fa ul t zone si nce the Miocene may amount to approximately 230 km (Ballance, 1976). In Miocene time the Hikurangi Trough was si tuated closer to the present-day

21 3

The Makara Basin

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coast line (Fig. 13). The increased separation since that time is due to progressive widening of the East Coast Deformed Belt wi th contin ued accretion and imbricate thrust deformatio n of the inner trench-slope. During the development of the Makara Basin, the present-d ay volcanic arc (Taupo Volcanic Zone) did not yet exist. At that time, the Coromandel Arc was active ( Ballance, 1976), contributing volcanic detritus to the slope basins. Recent dating of rhyolitic volca nics in the Coromandel area ( Rutherford , 1978) supports thi s suggestion. Taki ng the 230 km dex tral offset and ant iclockwise rotation of the northern parl of the North Island (Ballance, 1976) into consideration , a satisfactory palaeogeographic reconstruction for the setting of the Neogene inner trench-slope fl ysch basins in the East Coast Deformed Belt can be obtained (Fig. 13).

A C KN OWL E DGME N T S

Over the years, many people have assisted us with our Hawke's Bay studies, either in the field , laboratory and dark room, or by discussing concepts and data. They come from different institutions, the New Zealand Geological Survey (GS), the University of Canterbu ry, Christchurch (UC), and the University of Auckland ( UA). We are very

2 14

G. J. Mn der Linge" and J. R. Pettinga

gra teful fo r their help, a nd would like to use this opportun ity to mentio n them by na me: Mr E. T. H. A nnear(GS), Dr A. G . Beu (G S), Mr A. Down ing (UC), Dr G . W. Gibson ( UA), Mr R. M. Ha rris (U A), Dr N. de B. l-fo rnibrook (GS), Dr R. H. Hoskins (GS), Miss C. A. Hu lse (GS), Ms Lee Leona rd (UC), MrW . M. Prcbblc(UA), Mr G . W. Richards (G S), Dr G. H. Scott (GS), Mr D. Smale (GS). Dr K. B. S~ rli (V A), Mr K. M. Swanson (UC), Dr G . P. L Wa lker ( UA). The man uscri pt was read by Dr D . G . Howell (U .S. Geological Survey, Menlo Park , Cali forn ia), Dr P. F. Ba llance (UA), and Dr P. B. And rews (G S), who ma de ma ny useful suggestions for ils improvement. One of us (J .R.P.) received fi na ncial assista nce fro m the Nati o na l Wa ter and Soil Conservat ion Orga ni sati o n, Mi nistry of Works a nd Develo pment , a nd from a Postgraduate Scho la rshi p, a warded by the New Zeal a nd Uni versity Gra nls Com millee. Miss Christina M. Jo hnstone (GS) typed the va rious versions of the manuscript.

REFEREN CES BALLANCE, P.F. (1976) Evolu tion of the Upper Cenozoic Magmatic AI"(: and I'late Boundary in Nonhern New Zealand. Eorlll NOlin. Sci. ull. 28, 356-370. BoUMA, A. H. (1972) Recent and ancient turbidites and contourites. Trails. GIII/CSf. Ass. geol. Socs. 22,205- 22 1. ENOS. P. (1977) Flow regimes in debris flow. Sl'diml'IIfOlogy, 24,1 33- 142. FOLK, R.L., ANOItEWS. P.B. & LEWIS, D.W. ( 1970) Detrital sedimentary rock classirtcation and nomenclature for use in New Zealand. N .Z. J. Gro/. Gf!opll)'s. 13,937-968. GROW, J .A. (1973) Crustal and upper ma ntle strUl;ture of the central Aleutian an::. Bllfl. gro/. Soc . Am. 84, 2 169-92. HAl»-rZSCHEL, W. ( 1975) Trocf!/ossifs and problemOlico. Part W, supplement I (miscellanea) of Treatise on Invertebrate I'aleontology (Ed. by C. Teichart). Geological Sodny 0/ AmtrlcCl. 269 pp. KAR IO, D.E. & SHARMAN, G.F. ( 1975) Subduction an d aec::retion in trenches. 8ull. geol. Soc. Am. 86, 377- 389. KINGMA, J .T . ( 19588) The Tongaporutuan Sedimentation in Central Hawkes Bay. N.Z. J. Gf!Ol. Geoph)'s. I, 1- 30. KINGMA J .T. (l958b) Possible origin of pierce me nt st ructures, local unconformities, an d seconda ry basins in the Eastern Geosyncline, New Zeala nd. N. Z . J. Gool. Geophys. 1,269- 274. KING MA. J.T. ( 1960) The tecto nic significance of graded bedding in geosyncli na l sed imentary systems. III/.geol. COl/gr. 21. Cope nhage n, 205- 214. KI NG MA, J .T. ( 197 1) Geology o/ Te Allie sli/xIil'l·sioll . Bull. geol. S liry. N.Z. 70, 173 pp. KIJE NEN, Pfl.H . ( 1960) Turbidi tes in Mak ara Basin, New Zeala nd. Proc. K. Ned. Akad. Wei . Sa. B. 63, 127-34. KIJENEN, PIt .H. ( 1970) The turbi dite problem : some comments. N.Z. J. Gool. Geopilys. 13,852- 57. LEWIS, K. B. ( 1980) Quaternary sedimentati on on the Hik urangi oblique-subduction and tra nsform margin, New Zealand. In: Sedimf!lIlalioll ill obliqlle-slip mobile ZOIlI'S (Ed. by P. F. Ballance and H. G. Reading). Spec. Pllhl. i",. An. Sedimelll., 4, 171- 189. L£WIS, K.B. & KOHN. B.P. (1973) Ashes, tu rbidiles, and ra tes of sedimentation on the continental slope off Hawke's Bay. N.Z. J. Grol. Geopllys. 16,439-454. LILLIE, A. R. (1953) Geology o/I/re Dom/('~irke SlIbdi"isioll. &rll. gf!Ol. SlIn. N.Z. 46, 156 pp. LINGEN, G .J. VAN DEIt (19688) Preliminary sedimentological evaluation of some flysch-like deposits from the Makara Basin. Central Hawkes Bay, New Zealand. N.Z. J. Gl'Ol. Gl'Oplrys. II , 45s-477. LJ l»'(lEN, G.J . VAN OEIt (I968b) Volcanic ash in the Makara Basin (Upper Miocene), "Iawke's Bay, New Zealand. N.Z . J. Gl'ol. Goopilys. 11,693- 705. LINGEN, G .J. VAN DER ( 1969) The Tu rbidite Problem. N.Z. J. Grol. Geopllys. 12, 7-5 1. LINGEN, G .J. VAN DER ( 1970) The turbidite problem: a reply to Kuenen. N.Z. J. Geol. Gl'Opllys. 13, 858- 72.

The Makara Basin

215

LINGEN, G,J . VAN DER (1971) Granulometry of the Upper-Miocene flysch-type sediments of the Makara Basin, New Zealand. (Abstract). Vlllllllem. Sed. COJlgn.'ss. Heidelberg. Programme wilh abstracts. p. 59. MAItTlNI, J.P. & SAGRI, M. (1977) Sedimentary fillings of ancient deepsea channels: two examples from Northern Apennines (Italy). J. sl:dim . PetrQI. 47, 1542- 1553. MIDDLETON, G .V. & HAMPTON, M.A. (1 976) Subaqueous sediment transport and deposition by sedimen t gravity flows. In: Marini' sedinU!I//lrOJlsporl amI I'II_ir01ll1l1'1II01 mallogemelll (Ed. by D. J. Stanley and D. J. P. Swift), pp. 197- 218. John Wiley, New York. MOORE, G .F. & KARIG, D.E. ( 1976) Development of sedimentary blsins on the lower trench slope. Geology, 4, 693- 697. PElTINGA, J. R. ( 1976) Structure and slope failures in Southern Hawkes Bay. Abslr. geol. Soc. N.Z. Hamilton Conference. 1976. PElTINGA, J .R. ( 1977) Geology and regional significance of the EIslhorpe Ant icline, Southern Hawkes Bay. Abslr. geol. Soc. N.Z. QueenstOwn Conference. 1977. PElTINGA. J.R. (1980) Geology alld lalldslides o//hl' eastern Te Allie Dis/ricl. SOli/hem HC/h·ke's Bay. Unpublished Ph .D. thesis, University of Auckland. 602 pp. RI CC I- LuCCHI, F. ( 1975) Depositional cycles in two turbidite formations of Northern Apennines (Italy). J. sedim. Petrol. 45, 3-43. RUTI1 ERFORD. N.F. (1978) Fission-track age and trace element geochemistry of some M inden Rhyolite obsidians. N.Z. J. Geol. Geophys. 21, 443-448. SMITH, G.W., HOWELL, D.G. & [NGEItSOLL, R.Y. (1979) Late Cretaceous trench slope basins of cen tral California. Geology, 7, 303- 306. SPORLI. K.B. (1980) New Zealand and oblique-slip ma rgins: tectonic development up to and during Ihe Cainozoic. In : Sedilllelllo/iOIl ill oblique-slip mobile zolles (Ed. by P. F. Ballance & H. G . Reading). Spec. Publ. illi. Ass. Sedilllelll., 4, 147- 170. WALCOTI, R. I. (l978a) Presen t tectonics and Late Cenozoic evolulion of New Zealand. Geophys. J.R. aSlr. Soc. 52,1 37-164. WALCOTI, R.I . (1978b) Geodetic strains and la rge earthquakes in the axial tcclOnic belt of North Island, New Zealand. J. geQphys. Res. 83, 441 9-4429.

Spec. Publ. into Ass. Sediment. ( 1980) 4, 2 17-228

Late Cainozoic sedimentation and tectonics of the East Coast Deformed Belt, in Marlborough, New Zealand

W A RWI C K M . PR E BBLE Dep(trfmellf a/Geology, Unil'ersity

0/ Auckland,

New 2mlwu'

ABSTRACT The character of sedimentation in northeast Mar lborough changed markedly during the Miocene. when long-established, dominantly calcareous deposit ion gave way to an innux of clastic detritus. Conglomerate. breccia, olistostromes, sandstones and turbidites then predominated and are described from the coastal section of the shallow fold an d fa ult belt. between the Kekerengu and Waima Rivers. The change in sedimentation was preceded by submarine volcanism and accompanied by rapid tectonic uplift, a ma rked increase in sedimentation rate, exposure of older indurated undermass rocks and localized sedimentation of the very coarse clastics. These often chaotic deposi ts, collectively referred to as the Great Marlborough Conglomerate. fonned from partly coalescing submarine slides and debris nows. The sequence is conformable, wit h substantial variations in thickness of the clastic units and interfingering of the rudites with sandstones, turbidites and mudstones. Localization of the type and size of megaclasts is a conspicuous feature. The Conglomerate is restricted to the major fault-angle depressions and thickens rapidly towards the faults. Massive slope failure of the rising fault blocks supplied the coarse debris to the fau1t..controlled basins. A tra nsition from marine to non-marine deposition through the Miocene is seen from the southeast to the northwest. Sedimentation continued into the Pliocene, after which the covering strata were subjected to imbricate th rust fa ult ing and fo lding alo ng a northeast trend, parallel to the obliq ue·slip marg in. Subsequent ly, dextral fau lt ing o n the same trend has ro tated the covering slab of the shallow thrust and fold belt, which was uncoupled from the undermass as a tecton ic decollemen t in the Ben More block. This decollement is related to a major dextra l fracture-the Kekerengu Fault. Another dtcolJement is post ulated to occur over the northernmost sector of the Clarence Fault. A transition occurs in the Marlborough region from late Oligocene subduction and compression to Miocene normal faulting, Pliocene-eariy Pleistocene normal oblique-slip and late Pleistocene-Ra.:ent reverse oblique·slip. The M iacene-Recent movements have been concentra ted on the major faults of the region : Wairau (Alpine), Awatere, Clarence, Hope and Kekerengu.

I NTRODUCTIO N

The tectonically active, moun tainous region of Marlboro ugh forms the northeastern portion of the South Island of New Zealand ( Fig. I). The terrain is 0141-)600/ 80/0904·0216S02.00

\0 1980 International Association or Sedimentologists

218 '70

o

W. M. Prebble N

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Fig. I. l ocalit y map showing the position of the Marlborough district within the East Coast Deformed Belt and important features of the swdy area.

controlled by major northeast tfending dextral fa u lts, each of which has a highstanding upthrown block of Mesozoic undermass rocks on its northwestern side. In t he fault-ang le valleys Upper Cretaceous and Cainozoic covering stra ta are preserved in elongate strips which are complexly fau lted a nd fo lded. T hese cover beds ma rk the southern end of the Easl Coast Deformed Belt (Spt)rli, 1980), a zone of Cainozoic tecton ism which parallels the Hikurangi T roug h and , by inference, the oblique-slip margin. Between the Kekerengu and Ure Rivers ( Fig. I), the covering strata are most extensive and probably attain their greatest thickness fo r the Marlborough region. T hey form a com plex plunging anticline, the Ben More anticline (Prcbble, 1976), which is wrapped around a core of indurated Mesozoic undermass strata, forming the Ben More Block (Figs I and 2). Th is paper describes the Miocene rock s, and their deformation as part of the cover, in the Ben More Block and near Kekerengu (Figs I and 2). Similar Miocene strata to the south have been described by Laird & Lewis (1979). An extensive strip of covering strata which includes Miocene rocks occurs to the southwest alo ng the fault -angle Clarence Valley, a small sector of which has been described by Hall ( 1965).

5km

219

Tectonics of the East Coast Deformed Belt o o

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New Zealand stage names are given in parentheses after the in ternati onal equivalent. THE UNDE RMA SS STRATA AND THE IR R ELA TION S HI P TO T H E C OVER BED S Structurally, and lithologically, the cover in this block is fundame ntally di ffere nt from the undennass and much less indurated , although onl y some 6- 10 m.y. sepa rate them. The break between the undermass and the cover is, in part, an unconformity and , in part, a complex fault , the two merging into each other. The fault is interpreted as an undermass/cover decollement in the eastern half of the Ben Morc Bl ock. Wi thin thi s block, several more or less parallel fa ults and fol ds (Fig. 2) which arc confined to the Uppcr Cretaceous-Tertiary cover swi ng in an arc around the anticlinal core of undermass strata. Thi s arcuate pattern is exceptional in Marlborough and perhaps throughout the whole of the East Coast Deformed Belt. TH E COVE RI NG STRATA PRIOR TO TH E M I OCENE Throughou t the East Coast Deformed Belt, Upper Cretaceous through to Oligocene strata are characlerized by widespread fine-grained facies, in which siliceous

w.

220

/If. Prebble

shale, chert and miCri t ic argillaceous limestone are dom inant. In Marlborough, calcareous deposi tion concluded with an Upper Oligocene (Waitakian) marine calcareous mudstone and was accompanied by andesitic and basaltic sills, breccias, and pillow lavas. Oligocene tectonic activity is indicated by intraformational disharmonic folding which is common in the midd le units of the ArnuTi Limestone (Hall , \965; Prebble, 1976). Attributed to slump fo lding, it is considered to have occurred at the same time as a latc Oligocene unconformity recorded by Lewis, van der Lingen & Smale ( 1977) from North Canterbury. These events are minor compared to later tectonism. Similarly, the Upper Cretaceous- Oligocene strala, although widespread , attained only 1500 m of thickness in approximately 60 m.y. By contrast, Miocene sedi mentation reached a similar figu re in 10 m.y., but is much more localized .

TH E M I O CENE STRATA

The uppermost Lower Miocene (A lton ian) is marked by a sudden influx of conglomerate, breccia, diamictite and olistostromes, These rudites are known as the Great Marlborough Conglomerate ( McKay, 1886). Thick beds, lenses and tongues occur along a 10 km coastal strip centred at Kekerengu, where it attains its greatest known thickness and in terfi ngers wi th calcareous mudstone (Waima Formation), massive sandstone (Ti rohanga Sandstone) and thick mudstone, turbid ites, laminated sandstone and marl of the Heavers Creek Formation, Upper Mi ocene freshwate r conglomerate is widespread in the north of Marlborough, being derived from the rising mou ntain blocks north of the Awatere Fault (F;g. 3).

LEG EN 0

~

Pliocenefmorl ne )

§!] Upper M ioc en e ( f res hwoter) r;;;;-;;I Uj)per M iocen e t..::::..J (morine) ~

M iCCle M ioce ne

~ Conglomero t e brecc ·

~ io,Ciomieti t e,01isto ' ~ t ro m" $ .

r'"'1

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SOMUtQl1 e,m"d· stone, I lysch

~ Pr e ' MIocene

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FAULT

0

1 0W30

40~ . m

, ... " ' ·0

Fig, 3. Generalized distribution of Miocene and Pliocene

stra ta

in Ma rl borough,

Tectonics of the East Coast Deformel/ Bell

221

Great Marlborough Conglomerate The Conglomerate is massive, unsorted and well consol idated. Clasts vary in size from pebbles to large angular blocks and rans longer than 10 m. Most are less than 5 m long. In some exposu res pebbles and boulders dominate; in others large angular blocks. Rans up to hundreds of mel res in length have been mapped by Prebble (1976) near Kekerengu, and Hall (1965) several kilometres to the northwest. The largest occur in groups, with their greatest surface area parallel to bedd ing within the raft and to the crude bedding of the surrounding conglomerate. Smaller clasts generally have a random orientation. (Fig. 4).

Fig. 4. Dia mictite or the Great Marlborough Conglomerate. in Marlborough District

Heavc~

Creek near Ke kerengu,

The matrix of the conglomerate is a slightly muddy sandstone. In many exposures, the deposit is essentially a diamictite. The most common clast lithologies a re Amuri Limestone, a nd indu rated Lower Cretaceous sandstone. Minor lithologies include a range of igneous rocks derived from

W. M . Prebble

222

both the Cretaceous undcrmass plulons of the Inla nd Kaikou ra Block and the La tc Oligocene volcanics of the cover, splintery sha le, che rt, gla uconi tic sa ndstone, soft calcareous mudstone and sort calcareous bentonitic shale. One or two lithologies arc usually domina nt at a ny pa rticular locality. suggesti ng a very loca l derivat ion. Clasts of undermass origin are a bsent at some loca lities, but are commo n to predomin ant

at others. The diamictite texture, and the presence of large blocks of lo w-strength and fractured rock, imply a depositi onal mechani sm with matrix suppor! and witho ut turbu lence, i.e. debris fl ow. Crude d iscontinuo us strati fication is evident in the conglomerate. Truncat ion by o ther beds, although co mmon, is indistinctly shown, suggesting deposit ion in a series of mu ltiple a nd complex c hannels a nd lo bes. Beds of laminated, carbo naceous sandsto ne and graded sandsto ne- mudstone beds occur in units up to 45 m th ick which interfin ger with the conglo merate. The conglo merate fine s gradati ona lly upwards into sa ndsto ne and then repetiti ve sequences of graded beds. The basal contact of conglomerate o verlying these un its is sha rp, undula ting a nd channelled, with large ripped-up blocks of the d ist inctive laminated sandstone im mediately above the contact. Some erosive co ntacts a re highly co mplex, with nu mero us rip-up clasts and deep channels, the sides of wh ich a re often hi ghly irregu la r, presumably as a consequence of multiple super position of channels and debris lo bes. The interfi ngering is indicated by detai led mapping (Fig. 5). The thickness of the Great Marlborough Conglo me rate ranges up to 300 or 400 m near Kekerengu and up to 550 m furth er inla nd. In general the conglomerate thickens westwards, towards the Kekerengu Fault a nd thins ea stwards especia lly in the northeast where it d wind les rapidl y to a few metres and is re placed by sandstones and fin er clastics. A few of the la rge rafts have been deposited beyond the main body of conglomerate, within the fin er grained sedi ments. The Great Marlborough Con glomerate is conformably underla in by, and interfin gers with, si ltstone of the Waima Formatio n which is late Oligocene- earl y M iocene in age. Foraminifera fro m sandsto ne and mudstone beds within the conglomerate indicate that its a ge is latest early Mi ocene and mid-M iocene (Altonian to Waiauan), and tha t it is ma rine. H ea\"Crs Creek Formation Carbo naceous sandstone, graded sandsto ne- mudsto ne beds a nd massive mudsto ne overlie a nd interfin ger with the G reat Ma rlboro ugh Co nglomerate. They are 650 m thick in the Kekerengu a rea and are widespread thro ugho ut northeast Marlbo ro ugh. The sa ndsto ne beds are considered to be mass flow deposit s a nd the graded sandsto ne- mudstone beds indicate depositi o n by turbidity currents. The massive mudstone, which contains calcareous lenses, has been deposited from suspension . Foraminifera fro m nea r the base of the fo rmati on at Kekerengu give a n early to mid-M iocene age. Further to the northeast, fl ysch, conglomeratic sandsto ne, ma ssive mudsto ne a nd shell beds are late Miocene and Pliocene in age (To ngaporutua nWaitotara n). Massive sandstone bodies In the northeast of the region, the Lowe r Mi ocene medium quartzose Tirohanga

223

Tectollics of the East Coasl Deformed Bell

Sandstone interfingers with calcareous mudsto ne a nd pebbly mudsto ne (Waima Formatio n) in large elongate uni ts 80 m thick, and also as a large mu ltiple lens-shaped body up to 250 m thick (Fig. 5). Thin beds or conglomera te con ta ining indu ra ted

LEGEND

'. r.S.

MIOCENE F'ORMATIONS

IH.CF.IHe o"e..~ O"eek F'onncl ion ~JGl"ec t McrlbO~gh

Cong'Omercte.

1 : ~s::'.l TI.-ohcngc Sond~ton e ,r,.!?' RoIU ond

oll~ tollth~

01

IIm e ~tone In the Greot Morlborough Cong lom ercte. "( Oi" cnd ~trike youngi ng

~

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XSynclinol o .. l~

.' •".'

l

f

rli, 1980), there is no evidence tha t the other raults existed berore the Miocene. Later vertical movement on the Marlborough raults has been concentrated in the northeast, where it has created the Kaikoura Ranges. Substantial delttral movement in Marlborough has certain ly occurred in post-Miocene time, but a questi on or particular interest in this study is whether it may have been initiated during the Miocene. Late Miocene and Plio-Pleistocene tectonics An initial compressive phase accompanying lim ited subduction in the laiC Oli gocene was replaced by rapid dip-slip movement on the new-formed Marlborough Fault system in the early and mid-M iocene. These strong dip-slip movements persisted into the Late Miocene with substantial block raulting and tilting continuing, especially along the Wairau (A lpine) and Awatere Fau lts. The Clarence and Kekerengu faultangle depression in the East received mainly finer grained clastics and even calca reous mudstones in the Late Miocene, indicati ng a localized quieter phasc, synchron ous with the rapid uplift and accumulation or conglomerate in the west. During the Pli ocene, emergence of the rault-angle depressions commenced and was complete during the ea rly Pleistocene. Pliocene and early Pleistocene raulting was dominantly normal , wi th substantial ti lting and a dextral component (Lensen, 1962). Late Pleistocene-Holocene faulting has becn dominantly delttral, with a compressional componen t appearing on all the major rau lts ( Lensen, 1962 ; Prebble, 1976). Hence a transition can be recognized in Marlborough rrom compression and subduction (late Ol igocene) to dip-slip block rault ing (Miocene) to oblique slip, normal fau lting (Pliocene- Early Pleistocene) and oblique sl ip, reverse fa ulting (late Pleistocene- Holocene). Hence compression is a comparatively new reature, a conclusion reached also rrom sea floor spreading data by Walcott (1978).

D I SCUSS I ON It is interesti ng to consider the Miocene or the Marlborough sector of the East Coast Derormed Belt in the light or criteria discussed by Read ing (1980) ror the recognit ion or old strike-slip orogenic belts. Those which are clearly recognizable in Marlborough (ill (uifJitioll 10 Ihe tlireel e~idellce fo r laler oblique dextral mOfion) include the rollowi ng: .

fig. I . Map of New Zealand to show the zone of recent oblique-slip and locations of Figs J, 4 and 5.

Models of sedimellt distriblltion

231

Sediment so urces are moved progressively downstream and the earliest appearance of sediment from a given source is isochronous throughout the basin. The latest appearance, however, is diachronous, getting younger downstrea m and in the di rection of a strike-sli p motion, from different sources on both the rising and sinking blocks. T he stratigraphy of mixtures of sed imen t from different sources is shown diagrammatically in Fig. 2a, where sediment supplied from sou rce rocks upstream on the risi ng block is mixed with sediment supplied locally from the sink ing block. As source rocks on the risi ng block are carried downstream, their contributions successively disappear from the mixture. A New Zealand example of Model I is shown in Fig. 3. Model 2. Rivers on a sink in g block flow parallel to the fault and in the opposi te direction to strike-slip motion on the rising block (Fig. 2b). Sediment is carried in the opposite direction to the strike-slip motion on the rising block. Sediment sources are moved progressively upstream. In contrast to Model I, the ea rl iest appearance of sediment from a given sou rce is diachronous, gelling younger upstream and in the direction of strike-sl ip motion of the rising block, while the latest appearance is isochronous. In the same way, the stratigraphy of mixtures of sediments is the reverse of that in Model I (cf. Fig. 2a and 2b). As source rocks on the rising block are carried upstream, thei r con tribut ions are ({(Med to the mixture. A New Zealand example of Model 2 is shown in Fig. 4. Model 3. Sediment di spersal is now transverse to the fa ult line and fu nnelled th rough a gorge in the sinking block (Fig. 2c). Sediment from a particular source on the rising block has a restricted distribution in the proximal part of the fau lt-angle depression. In contrast to Models I and 2, both the earliest and latest appearances of such sediment arc diach ronous, gelling younger in the direction of strike-slip motion on the rising block. Sediments from different sources occu r in a stratigraphic sequence which is the same as the order of arrival and departure of those sources. Mixing of sediment increases distally from the rising block, and the contribution from the downsinking block is minimal. The Ruataniwha Depression is an example of Model 3 (Fig. 5). Model 4. Rivers flow away from the rising block directly to the sea ( Fig. 2d). This model is a modification of Model 3, and all aspects of stratigraphy, diach ronism, and mixing of sedimen t are the same. There is no co ntribu tion of sediment from a downsinking block. However, such tectonic depressions tend to be larger than the simple fault-angle depressions considered in Models I to 3, and may receive drainage along the strike from a wide variety of terrai ns. T he most st rikin g New Zealand exam ple of Model 4 is the Heretaunga Plains tectonic depression, Hawke's Bay, eastern North Island (Fig. 5). This large tectonic depression truncates a number of fault blocks and folds on its southern margin, and gathers a number of major rivers. Other examples occur on the West Coast of the South Island, forming extensive alluvial plains between lhe Alpine Fault and the Tasman Sea.

232

P. F. Ballance DRAINAGE IN THE SAME DIRECTION AS STRIKE-SLIP

MOTION ON UPLIFTED BLOCK

,.

,"",

.

• • A'•C •

...

,

A RARA-l exploration well. Regional time-isopach maps for Ihe lower seismic units (Eocene to early Mi ocene) show both basins were filled largely from their western margins; since no source regions exist to the west of either basin today, il is inferred th at they have been shifted northeast by lateral movement on the Alpi ne and Moonlight fault systems. Time-isopach maps for the upper seismic uni ts (late M ioce ne to Recent) show the Balleny Basin to have received a thin, main ly pelagic dra pe, whereas the Solander Basin has been filled by a thick. shelf sequence, prograding from off the so uthern end of the New Zealand landmass. The deve lopment of the basins of so uthwes t New Zealand is re lated to th e behaviour o f the Fiordland microplate, a rigid block. of co ntinental crust located betwee n the Moonligh t and Alpine fault systems. During the Eo-Oligocene, ex tellsional oblique-slip (transtens ion) on these fault systems led to the subsidence and final submergence of Fiordland. Compressive oblique-sli p (transpression) since the middle Miocene has caused a northwards movement of the microplate, with associated deformation and uplift reaching a maximum in the north and decreasing in intensi ty southwards. The main modern drainage sys tems have thereby developed from north to sou th, more or less along the line of the M oonlight tecton ic zone.

I NT RO D UCTI O N The IndO-Australian/ Pacific plate boundary crosses the New Zealand continental plateau as the Alpine oblique transform fa ult system (e.g. Walcott, 1978). Plate tectonic arguments, based on marine magnetic anomalies in the southwest Pacific Ocean, 0 14 1-3600/ 80/0904-0237502.00 10 1980 International Association of Scdimentologists

238

R. J. Norris and R. M . Carter

date the incepti on of this plate boundary during the Eocene (Molnar el 01., 1975 ; Weisse\, Hayes & Herro n, 1977). Between the Late Cretaceous a nd Eocene the New Zealand continent was emergent but of generally low relief; shallow seas transgressed on lO the landmass, restricting non-marine, coal measure sedimentation to a progressively narrowing central belt (Crooks & Carter, 1976 ; Norri s, Carter & Turnbull, 1978). In the latest Eocene and Oligocene this regionally uniform marine transgression was disrupted by tecto nic act ivity in western New Zeala nd, followed in the ea rl y Mi ocene by arc-volcan ism in northern North Island (Pilaar & Wakefield , 1978; Nelson & Humc, 1977). Clearly, movement had commenced on the Alpine plate boundary. The subsequent tecton ic history of thc plale boundary inferred from geology is in close agreement with that infer red from geophysics (Ballance, 1976; Carter & Norris, 1976). In southwestern South Island, southeast of the Alpine Fault, Cretaceous-Eocene coal measure fa cies are sharply followed by thick flysch sequences of latest Eocene and you nger ages. Post-Eocene sedimentation occurred in active, fault-bounded marine basins, often at bathyal depths. Indi vidual basins were often on ly a few to a few tens of kilometres across, but regionally they form ed a linked sed imen tation system controlled by the Moonlight Tectonic Zone. The most recen t manifestation of the Moonlight Tecton ic Zone is a system of Late Mi ocene to Holocene highangle reverse fau lts wh ich extend from north of Lake Wakatipu southwestwards to the coast a t Te Waewae Bay (Tu rnbull er al., 1975). The modern intermontane Te Anau a nd Waiau basins lie respectively to the northwest and southeast of this Moonlight Fau lt System (Fig. I). Due to mid-Miocene a nd later tectonism, resulting from major transpressio n along the ma in Alpine transform ( Molnar el ai. , 1975), it is difficult to reconstruct the origi nal size, shape or disposi tio n of the Oligo-Miocene fl ysch basins. The Moo nlight Fault System joins the Fiordland Boundary Fa ult System near Lake Mo nowai (Figs I, 2 a nd 4), and continues offshore as the boundary zone between the Salleny a nd Solander Basi ns (Figs 4,5). Seismic profiles of the offshore region show a pattern of fault-bounded basins similar to that envisaged for the on land examples prio r to their eversion, with the intensity of deformati on of the sedimentary sequence decreasin g southwestwards. Basinal sedimentation continues offsho re today in the head of the Solander Trough. Though few detailed studies have been published, the onland sedimentary history is now moderately well understood. In contrast, there are virtually no publi shed data available for the offshore region . We present in this paper the results ofa preliminary analysis of oil exploration sesimic data from some I g 000 square miles of ocean offshore from southwestern South Island, interpreting the data in the light of o ur knowledge of nea rby on la nd geology.

Sources of data During 1970- 1, seismic data collected by Hunt International Petroleum Company (H IPCO) from the offshore Te Waewae Bay a nd Solander Trough regio ns ( Fig. 2) were used to locate wildcat well PARARA-I in 484 feet of water in the head of the Solander Trough. In late 1977 more than 3000 km of seismic da ta (Fig. 2) and the log of PA RARA-I became available o n open. fi le (HI PCO, 1970, 197 1, 1976).

Offshore sedimen/ary basins o/the Alpine Faull

239

AREA OF

!...... I H

Sediments

Schist RANGITATA

Low g rade metased i ment ~

SEQUENCE (Perm ia n Jura ss ic)

Ba sic igneo us rock s Gran ite

,"d

TUHUA

SEQUENCE Pre€:. - Dev.J

,'1'1',',','

High g rade met amorph ics 'F Iy sch'

Fig. I. Locality map of southwestern South Island. T : Te Anau Basin; W: Waiau Basin; D. M .O.B.: D un M ountain Ophiolite Belt; M .T.Z.: Moonlight Tectonic Zone. Sequence nomenclature after Carter ('I al. (1974).

240

R. J. Norris Gild R. M . Carter

-, '" 1

I

_\

~\ ~

~\ 3\

Srcwo.t h lond

I

' I /

/

Offshore PPl 38013 50 ~ '"

Fig. 2. Locati on of major seismic survey lines availa ble from area of offshore Petroleum Prospecting Licence 38013, southwestern South Island. Lines reproduced in this paper (Figs 6--10) shown in heavier ink. C: Chalky Island ; S: Solander Island ; P: PARARA·l well.

Most ofthe seism iccovtr is 12-fold COP with an Aquapulse source, a lesser amoun t being in single or several channel form. Though the seismic data is available in fie ld processed form on ly (i.e. aft er preli minary stacking and deconvolution), in most cases interpretat ion is clea r, with penetration of stratified sequences to depths in excess of 4 s two-way travel time. Some areas of intense faulting, particularly along basi n margi ns, are so overlain with diffraction hyperbolae that unambiguous interpretation is not possible in the a bsence of migrated sect ions. Two main scales of seismic line are available. We have prepared typical crosssections (Figs 6-10) and li me-isopach maps ( Fig. l2a- d) largely from an analysis of

Offshore sedimentary basins of the Alpine Fallll

241

the smaller scale Band D lines of Fig. 2. The larger scale A lines were used for checking important stratigraphic or structural detai l. In addi tion, we show all regional structural fea tures on a composite 'basement ' map (Fig. 4).

REGIONAL STRAT I G RAPHI C H IS TORY

The tectonic and sedimen tary complexity of the Neogene succession in southwestern Sou th Island ma kes it difficult to devise a simple and econom ical nomenclatu re. In the sum mary of regional stratigraphy presented below (cf. Table I) we have therefore adopted a primarily chronostratigraphic subdi vision. Our sum mary is based on more detailed work described in McKellar (1956), Bowen ( 1964), Wood ( 1969), Su therland ( [969), Mutch ( 1972), Landis (1974), Turnbull et al. ( [975), Carter & Lindq vist (1977), and Ca rter & Norris (1977a, b); less detailed, regional discussions are presented by Katz (1968), Carter & Norris (1 976) and Norris et al. ( 1978).

Cretaceous and Early Cainozoic non-marine strata Locally, as at Ohai ( Fig. 2), the basal sediments in southwest South [Sland are thick sequences of immat ure, mid-late Cretaceous coal measures, located in postRangitata faul t-angle depressions (Bowen, 1964). At Sand Hill Point on the south coast of Fiord land, a non-marine, red bed fang lomerate sequence over 300 m thick may be as old as ea rly Cretaceous. These older non-marine beds are fo llowed, unconformably al Ohai, by younger Eocene- Oligocene coal measures of the Nightcaps Group, which lap ou t of the faul t-bounded troughs to form a regional blanket of nonmarine deposits unconformably overlying weathered basemen t (Wood , 1966). Duri ng the Late Cretaceous and early Cai nozoic, therefore, ini tial rel ief on a tectonically stable post- Rangitata landscape was reduced by erosion and infill ing of the block-faulted topography. By late Eocene time peneplanation was well advanced over wide areas, particularly in the northeast. Eo- Oligocene tectonism and basin formation The mature Eocene land-surface was abruptly affected by a phase of tectonism in the latest Eocene and ea rl y Oli gocene. Rapid marine incursion was accompanied by deposit ion of thick breccia, arkosic sa ndstone and fl ysch in fault-bounded , deep marine basins. In the west, at Chalky Island, the lower mass-emplaced sed iments pass upwards into nan no-chalk marls ; the Balleny Group, though almost I km thick, enti rely falls within a single faunal zone of early Oligocene age. Further east, in the fa ult-controlled Waia u and Te Anau Basins, Oligocene redeposi ted marine sequences over 2 km thick occu r ( Fig. 3), but lack the chalk marl facies of Chalky Island. Basin margin sequences of Ol igocene age are known, particularly along the western side of the Te Anau and Waiau Basins (Fig. 3). Shallow water, calcareous arkosic sands, and molluscan , algal and bryozoan limestones are typical lithologies (Poin t Burn and Tunnel Burn Formations; McKellar, 1956). Sequences are thin , usually several tens of metres, and contain Oligocene paraconformi ties (cf. Hyden, 1975 ; Carter & Norris, I 977b).

R. J. Norris and R. M. Carter

242

Early Miocene deprcssion Basin-margin sequences on the west side of the Waiau and Te Anau Basins arc followed abruptly in the early Miocene by deep marine mudstones (Garden Point Formation) which grade upwards into early to middle Mi ocene flysch of northern Table I. Summary lithostratigraphic table for Ka ikoura Sequence deposits of southwestern South Island. Unconformities are represented by oblique hachuring ; asterisks in left-hand column refer to phases of tectonism AGE

~

s. FIOROlAND Tl'ITgcl> ~Is

TE ANAU GloclGl

.~

:0 0

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.~ ~

.~

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11

243

244

R. J. Norris and R. M. Carter

reduced in thickness or absent across this unconformity, indicating another regionally significant tectonic pulse. Lale M iocene to Recent sedimenta tion Following the late Middle Miocene tectonism, marine sedimentation was restricted to areas within a nd southwards of the southern Waiau Basin . In the Te Anau and northern Waiau Basi ns, flu vial molasse, and later glacial, deposits constitute the sedimentary record up to the Recent. In the southern Waia u Basin, coarse-grained shallow marine sediments of latest M iocene age (Po rt Craig beds, Table 1), pass up into deep marine mudsto nes with bathyal faunas (Waikoa u Formation), which arc in turn overlain by shallow marine sediments of Pliocene age (Te Waewae Formati on). Further west, in the Wairaurahiri Syncline (Fig. 4), thick latc Mi ocene mudstones and siltstones occur (Wood, 1960). Clea rly, in the south , further active basin depressio n took place during the latest Mi ocene, but except near major faults this has been foll owed by relative stabil ity during the fina l regressional sedimentary phase.

ST RUC T U R E A N D SE I SM I C STR A TI G R A PHY

The offshore tecton ic and summary time-isopach maps (Figs 4, 5), and the seismic profi les (Figs 6-10), reveal that two major sedimen ta ry basins occur in the offshore area. The two basins, here na med the So lander and Balleny Basins, a re separated by a major zone of fa ults and basement uplifts which, when extrapolated to the coast, corresponds to the Ha uroko fault and associated fa ults of Wood (1966). This group of fa ults, wh ich represents the southwest continuation of the Moonlight Fault System (Norris el 01., 1978 ; cf. Fig. 13), is referred to hereafter as the Fiord land Boundary Fault Zone. Bo th offsho re sed imentary basins a re com plex in detai l, wi th intra ba sina l hi ghs and sub-basi ns. Though the dom inant fau lting is o riented NE-SW, both basins are bounded to the north by zones of NW-oriented cross-fault s; a sign ificant consequence is that the on land Waiau Basin is seen to be clearly distinct from the offshore Solander Basin (cf. Katz, 1974). In additio n to the structural interpretation of the seism ic profiles, presented in Fig. 4, the sedimentary fill of the basins has been di vided into a number of unconformity-bounded seismic un its, following principles discussed by Mitchum , Vail & Thom pson (1977). Because of the difficulty of tracing these uni ts across the Fiordla nd Bou ndary Fault Zone, a different designation is used for the seismic units recognized in the Balleny (Seismic Units 1--4) a nd Solander (Seismic Units A- D) Basins, even though the same number of units is recognized in each. Solandcr Basin Siructllre. The Solander Basin is bounded to the west by the Big River Highs and the Fiordland Boundary Fau lt Zone, to the no rth by the Hum p Ridge- Midbay High a nd to the east by the Stewart Island shelf (Fig. 4). Sou thwa rds the basin opens out into the head of the Solander T ro ugh. The Hump Ridge- Midbay High is a complexly fa ulted basement high which

Offshore sedimell1ary basins of the A/pille Fault

245

F" n:,\ ( · ~ .~T! ! . \ l1'

,I

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~ ""

.~ n: \\A I ('·

foul. at foul! lone ' kk on ne' down' hfOWn .ode

11'1.,\ :o. u

Syn< line An' ;':line

I o

D

Cen'", PARARA I

Fig. 4. Composite structural map of the offshore Te Waewae Bay- SolanI

....

}
1700m)

17'"'1 0 · 5-15 (650-1700m) L.:.:..:J

o

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UNIT 1 (we.rl &. UNIT 8 \ feud

Fig. 12. Time-isopach maps for the seismic un its mapped in the Te Waewac Bay-Solander Trough area. Arrows show the dirl:(;: \i on of sedimen tary downlap.

Offshore sedimentary basins of the Alpine Fault

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257

25

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