paleoenvironmental and tectonic changes across the cretaceous/tertiary boundary at tora, southeast...

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Paleoenvironmental and tectonic changes acrossthe Cretaceous/Tertiary boundary at Tora,southeast Wairarapa, New Zealand: A link betweenMarlborough and Hawke's BayM. G. Laird a , K. N. Bassett a , P. Schiøler b , H. E. G. Morgans c , J. D. Bradshaw a & S.D. Weaver aa Department of Geological Sciences , University of Canterbury , Private Bag 4800,Christchurch, New Zealandb Geological Survey of Denmark and Greenland , Thoravej 8, Copenhagen, 2400,Denmarkc Institute of Geological & Nuclear Sciences , P.O. Box 30 368, Lower Hutt, New ZealandPublished online: 21 Sep 2010.

To cite this article: M. G. Laird , K. N. Bassett , P. Schiøler , H. E. G. Morgans , J. D. Bradshaw & S. D. Weaver (2003)Paleoenvironmental and tectonic changes across the Cretaceous/Tertiary boundary at Tora, southeast Wairarapa, NewZealand: A link between Marlborough and Hawke's Bay, New Zealand Journal of Geology and Geophysics, 46:2, 275-293,DOI: 10.1080/00288306.2003.9515009

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New Zealand Journal of Geology & Geophysics, 2003, Vol. 46Lairdetal.—PaleoenvironmentatK/Tboundary,SEWairarapa: 2 7 5 - 2 9 30028-8306/03/4602-0275 $7.00/0 © The Royal Society of New Zealand 2003

275

Paleoenvironmental and tectonic changes across the Cretaceous/Tertiaryboundary at Tora, southeast Wairarapa, New Zealand: a link betweenMarlborough and Hawke's Bay

M. G. LAIRD1

K. N. BASSETT1

P. SCHIØLER2

H. E. G. MORGANS3

J. D. BRADSHAW1

S. D. WEAVER1

1Department of Geological SciencesUniversity of CanterburyPrivate Bag 4800Christchurch, New Zealand

2Geological Survey of Denmark and GreenlandThoravej 82400 Copenhagen, Denmark

3Institute of Geological & Nuclear SciencesP.O.Box 30 368Lower Hutt, New Zealand

Abstract The Late Cretaceous-Paleocene successionexposed on the Tora coast, near the southeastern tip of theNorth Island, is distinguished by an unusual lithofacies ofthe Whangai Formation, and by an apparently uniqueformation, Manurewa Formation, which spans theCretaceous/Tertiary (K/T) boundary.

The Late Cretaceous siliceous Whangai Formation at Toraincludes zones of slumps and olistostromes, containingmegaclasts of limestone up to 3 m long. The olistostromaldeposits suggest steep submarine topography with a highrate of erosion, and imply tectonic activity. The commonoccurrence of hummocky cross-stratification suggestsdeposition in shelf depths above storm wave base. Thesharply overlying Manurewa Formation is interpreted as theinfill of a major shallow channel complex, perhaps >9 kmwide and spanning the K/T boundary in time. The older oftwo channelled units is of latest Cretaceous (latestHaumurian/late Maastrichtian) age, and consists ofbioturbated alternating thin sandstone and mudstone withthin conglomerate lenses and limestone beds. It is likely tohave been deposited in a low-energy environment, probablydeeper than that of the Whangai. The younger channelsystem, of early Paleocene (early Teurian) age, erodes intothe older in the northeast, and into the underlying WhangaiFormation in the southwest. Basal deposits consist

G02013; published 30 June 2003Received 28 February 2002; accepted 10 March 2003

predominantly of medium to coarse, thick-bedded,glauconitic sandstone, with local low-angle cross-stratification and microflora typical of low salinityconditions, suggesting deposition in shallow shelf depths.These deposits contain olistrostromes with megaclasts upto 1 m long of limestone and rarer dark grey siltstone orvery fine sandstone clasts typical of Whangai Formation.The inclusion of megaclasts of Whangai Formation indicatesthat local emergence and erosion of older strata wasoccurring. Deposits grade upward into well-sortedbioturbated sandstones of the Awhea Formation, withprominent low-angle cross-stratification, interpreted as veryshallow marine, probably nearshore deposits.

The channel system represented by the ManurewaFormation records an initial relative sea-level rise, followedby an abrupt sea-level fall at, or close to, the K/T boundary.New Zealand was in a passive margin tectonic setting at thetime, but the widespread presence of olistostromes, someincluding clasts derived from older strata, suggest that localtectonic activity and uplift was occurring. The effects mayhave been enhanced by a climatic shift in storm tracks andintensity in the latest Cretaceous, which is supported by theevidence of strong wave activity.

By contrast, to the south in Marlborough, the K/Tboundary succession is commonly characterised by anapparently conformable lithologic change from limestoneto chert, although with local hiatus. To the north, in southernHawke's Bay, the coeval succession is characterised by adisconformity separating greensand from underlying lightgrey, slightly calcareous mudstone of the WhangaiFormation. The Tora sequence may provide the link betweentwo distinctly different lithologic successions.

Keywords Cretaceous; Paleocene; Cretaceous/Tertiaryboundary; Haumurian; Teurian; Maastrichtian; GlenburnFormation; Whangai Formation; Manurewa Formation;Awhea Formation; sedimentology; tectonics; sea levels;submarine channels; olistostromes; Wairarapa; East CoastBasin

INTRODUCTION

The tectonic setting throughout New Zealand from latestCretaceous-Paleogene times was a passive margin regime,subsequent to the opening by seafloor spreading of theTasman Sea and the Southern Ocean in the Late Cretaceous(c. 85 Ma). This had the effect of isolating New Zealandfrom Australia and Antarctica, and the period was generallymarked by subsidence and slow marine transgression,although there is evidence in some localities for an abruptdrop in relative sea level at, or close to, the Cretaceous/

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276 New Zealand Journal of Geology and Geophysics, 2003, Vol. 46

and Dido1 urala

&eclh7i tocotrv

Unatna

Fig. 1 Locality map, showinggeneralised geology of the Toraarea, and location of the sectionsstudied. Inset: The relationship ofthe Tora area to the East CoastBasin, and other localitiesmentioned in the text.

Tertiary (K/T) boundary (Moore 1989a). In eastern NewZealand, in the East Coast Basin, the latest Cretaceoussediments are commonly fine-grained outer shelf to bathyaldeposits, typically mudstone or micritic limestone (Field etal. 1997). These facies, reflecting a generally deepeningbathyal trend, become dominant through Paleocene times.Despite the passive margin tectonic setting, extensionalfaulting did not cease entirely, and Late Haumurian(Maastrichtian) faulting has been well documented in theSouth Island on the West Coast (Laird 1993, 1994), and innorth Canterbury (Nicol 1993). Late Cretaceous faulting hasalso been identified in the North Island in northern Wairarapa(Moore 1980).

The K-T transition also marks a period of climatic changefor New Zealand. A dramatic increase in siliceousmicrofossil abundance and chert above the boundary in theMarlborough region has been attributed to an increase insurface productivity, inferred to be due to enhancedupwelling (Hollis et al. 1995). It is possible that latestCretaceous climatic cooling in the Southern Ocean may haveinitiated an episode of more vigorous atmospheric circulationand disturbance, resulting in wind-driven upwelling (Holliset al. 1995). Changes in relative sea level at the same time

may also have affected the degree and location of thisactivity.

Since the publication of a description of the K/Tboundary section in Woodside Creek, northeasternMarlborough (Strong 1977), and its inclusion in the seminalpaper by Alvarez et al. (1980), a number of K/T boundarysections have been examined in detail. Most are located inthe southern, Marlborough, portion of the East Coast Basin(references in Strong 2000). One section from the northernportion of the East Coast Basin in southern Hawke's Bay atTawanui (Wilson et al. 1989) has been examined in detail.Others, from Hawke's Bay and Raukumara Peninsula, havebeen described in less detail (Moore 1989b) (Fig. 1).

The main purpose of our investigation was to examinein detail suitable sections through the poorly known K/Tboundary between the Southern Hawke's Bay andMarlborough regions in order to provide a link between well-studied successions to the north and south (Fig. 1). Inaddition, earlier reconnaissance studies in southeasternWairarapa recorded the presence of an enigmatic locallycoarse grained unit of uncertain latest Cretaceous to earlyPaleocene age (Manurewa Formation), which was apparentlyunique to the area (Waterhouse & Bradley 1957). Its

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Laird et al.—Paleoenvironment at K/T boundary, SE Wairarapa 277

Scalem

- 40

swTe Kaukau Point

i T T lTime Scale S

Pukemuri

Stream

NE

ManurewaPoint

..«-

. 9.5

A. homomorphum

g K / TBoundary

LEGEND

X^^\ siltstone

[ . ; . . ] sandstone

H&££J clast-s up ported|gy& conglomerate[• ens e matrix-supported' en se conglomerate[^.^| with outsize clastsll a ry limestone/

I-on e/ calcareous beds

thin - bedded

- bedded

hummockybedding

concretionsc bioturbation

g glauconite

F. —

I. cretaceum -*•• • • • • . ' • . • . • l . : - : - ' . : . / -

- F.

GLENBURNFORMATION

Fig. 2 Stratigraphic columns showing relationship of formations, main lithologic units, and the position of the K/T boundary insections studied in the Tora area.

occurrence appeared to be anomalous with respect to theother K/T sections and to the surrounding, regionallyextensive, fine-grained passive margin succession. Thus, theTora region offered an excellent opportunity to studypaleoenvironmental and relative sea-level changes, as wellas possible tectonism around the K/T boundary in NewZealand.

LATEST CRETACEOUS AND EARLY PALEOCENESTRATIGRAPHY OF THE TORA AREA

Previous work and geographic settingPrevious studies of the Late Cretaceous and earliest Tertiaryrocks of the Tora area of southeast Wairarapa are sparse.Waterhouse & Bradley (1957) included the area in adiscussion of the stratigraphy and sedimentation ofsoutheastern Wairarapa, and mapped four formations of LateCretaceous-Paleocene age: "Piripauan Sandstone", WhangaiFormation, Manurewa Formation, and Awhea Formation.The "Piripauan Sandstone" is now considered to be part ofthe Glenburn Formation, which was defined by Crampton(1997) as "…. all Ngaterian to Haumurian flysch facies strataon the Eastern Sub-belt in the southern Hawkes Bay-Wairarapa region". The Manurewa Formation appears to berestricted to the Tora area. Moore (1988a), in a study ofstructural divisions in the eastern North Island, included theTora area in his Tora structural block, which consisted of

the Tora area in the south, and the Glenburn/Flat Point areato the north, separated from each other and from adjacentstructural blocks by major faults. Moore (1988b, 1989a) alsopresented stratigraphic columns for the succession inPukemuri Stream at Tora, and speculated that the K/Tboundary coincided with an unconformable contact betweenthe Whangai and Manurewa Formations. A study by Lee(1995) of the Cretaceous-Paleogene geology of theHuatokitoki Stream area to the north (Fig. 1) also includedan examination of a reference section from Pukemuri Streamat Tora for comparative purposes; however, no significantnew information was recorded.

Exposure of Late Cretaceous strata in the Tora area isrestricted mainly to shore platforms and stream sections.Three well-exposed sections, 4-5 km apart, which wereinferred to include the K/T boundary, were examined indetail (Fig. 1, 2). Although all three sections containedWhangai, Manurewa, and Awhea Formations, only one(Pukemuri Stream) contained the underlying GlenburnFormation.

Glenburn FormationDescription

The Late Cretaceous Glenburn Formation crops out as anarrow coastal strip between the mouths of Pukemuri andOroi Streams (Fig. 1) on the northwest-dipping limb of anortheasterly trending anticline whose axis runs parallel to

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the shoreline. At the mouth of Pukemuri Stream, it is in faultcontact with the overlying Whangai Formation. Asedimentary contact was not seen. The formation consistsmainly of alternating fine to very fine, locally glauconiticsandstones and interbedded mudstones, with minorconglomerate horizons.

The lowest beds exposed at low tide consist mainly ofseveral metres of thin-bedded parallel-laminated sandstoneaveraging 10-20 cm in bed thickness, alternating with thinmudstone. Scattered, impersistent shallow scours up to 25cm deep occur at the bases of some sandstone beds, infilledmainly with granule to very coarse sandstone, but locallywith rounded pebbles up to 5 cm in diameter. Somesandstone beds show poorly developed normal grading, withthe upper portions of otherwise massive beds showingparallel lamination passing up into convolute lamination.Interbedded mudstones are commonly highly bioturbated,and both horizontal and vertical burrows occur.

Approximately 17 m above the base of the exposure,sandstone beds become thicker and massive without visibleinternal structures, averaging between 0.3 and 2 m thick.They have sharp bases, some with flame structures. Twocontiguous trough cross-stratified beds, with sets 15 and 25cm thick, occur 24 m above the base of the exposed section.Paleocurrents were directed towards the north.

Higher in the succession, packets of both thick (up to2.7 m thick) and thin-bedded (5-10 cm thick) sandstonesoccur interbedded with mudstones. Sandstone beds are sharpbased, commonly with flame structures, and many shownormal grading. The thinner beds commonly show parallelstratification with convolute lamination in the upper fewcentimetres, a few of them with Bouma ABC intervals. Onehorizon of possible hummocky cross-stratification wasobserved in the upper part of a sandstone bed, and probablewave-ripples were seen in another. The muddy interbeds arecommonly bioturbated, with both vertical and horizontaltraces. Some clumps of sandstone beds also show strongbioturbation. The trace fossil Zoophycos occurs sporadically.Carbonaceous layers are locally present.

Layers of granule to pebble conglomerate become morecommon in the upper part of the succession and arecommonly loaded into underlying sediments. One sandstoneunit contains a 0.5 m bed of low-angle cross-stratification.Another horizon contains channels up to 70 cm deep with aconglomerate of rounded pebbles at the base, consistingdominantly of sandstone and rhyolite. The overlying infillconsists of laminated slumped and loaded sandstones.

Paleontology and age

Trace fossils are abundant in the succession, but onlyZoophycos was identified at the generic level. Waterhouse& Bradley (1957) recorded poorly preserved macrofossilswhich "include Syncyclonema aff. membranaceus (Nilsson),Inoceramus australis (Woods), belemnites, and reptile boneswhich suggest a Piripauan age". Crampton (1996) consideredthat Inoceramus australis occupies the middle and upperparts of the Piripauan Stage. Dinoflagellates collected as partof the current investigation from c. 20 m above the base ofthe exposed succession (Fig. 2) include Isabelidiniumcretaceum and other species (Table 1), which co-occur onlyin the Late Piripauan I. cretaceum Zone of Schiøler & Wilson(1998) (Fig. 3). ALate Piripauan (early-mid Santonian) ageis therefore adopted.

«... •

Hit |^11» mJtl

irM-M-i MB-B&ai L

••R .miiLin

1 i::ii.i

finninn -* "Tmlmi

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Fig. 3 Summary correlation of dinoflagellate stratigraphy andNew Zealand chronostratigraphy with the international time-scalefor the Late Cretaceous and Paleocene. Chart is based on Stronget al. (1995), Crampton et al. (2000), Crouch (2001), and Cooperet al. (in press).

Environment of deposition

The common presence of sharp-based, normally gradedsandstone beds, some with Bouma sequences, in analternating sandstone-mudstone succession, suggestsdeposition from turbidity currents. This is supported byevidence of rapid deposition indicated by common load andflame structures at the bases of beds. The presence of atleast two horizons of large-scale cross-stratification,however, suggests that traction currents of sufficient strengthto transport coarse sand periodically swept the seafloor. Thepresence of possible hummocky cross-stratification suggeststhat the sediments may have been deposited, at least partly,above storm wave base. Storm waves may also have beenresponsible for the shallow scours near the base of theexposed succession. The trace fossil Zoophycos, althoughreported commonly from dysoxic facies in deeper parts of abasin (Bromley 1990), can also occupy inner-mid-shelfenvironments (Bottjer et al. 1988; Schiøler et al. 2002). Thehighly burrowed nature of finer interbeds, and the presenceof suspension feeding biota, indicated by the occurrence ofvertical as well as horizontal burrows, also suggests an activeseafloor environment. The environment is considered to bea basin within shelf depths, probably just above storm wavebase.

Whangai FormationDescription

The Late Cretaceous Whangai Formation is sporadicallyexposed on the shore platform between Manurewa Point and

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the mouth of Pukemuri Stream, for c. 500 m up PukemuriStream, and on the shore platform between Oroi Stream andTe Kaukau Point (Fig. 1). Whangai Formation reaches itsgreatest thickness of 200 m in Pukemuri Stream. However,its basal contact is faulted against the underlying GlenburnFormation, and its upper contact is truncated by an erosionsurface beneath the Manurewa Formation, so its fullthickness is unknown. Because of poor exposure elsewhere,no basal sedimentary contacts were seen.

The thick exposure of Whangai Formation in PukemuriStream (Fig. 1, 2) appears fairly uniform, consistingdominantly of massive, dark purple-brown siliceous siltstoneand very fine sandstone, with scattered horizons of jarositicefflorescence and zones of calcareous concretions, reachingup to 2 m in diameter. No interbeds of different characterwere noted. However, on the well-washed shore platformnorth of the mouth of Pukemuri Stream, probably separatedfrom the stream section by a fault, dark grey siltstone of theWhangai Formation includes horizons with scattered angularclasts up to 15 cm in diameter of mudstone, mediumsandstone, glauconitic sandstone, and fragments ofcalcareous concretions. Dikes of quartzose fine-grainedsandstone up to 20 cm thick and extending for several tensof metres across the shore platform are also common. Mostof the dikes have a northeasterly trend, with a smaller numbercutting these orthogonally, locally forming a rectangularpattern.

At the western end of Manurewa Point, a 30 cm thickexposure of Whangai Formation, consisting of brown-greysiltstone to very fine sandstone, with possible burrows andcontaining a small pebble of sandstone, underlies ManurewaFormation with sharp, irregular contact (block 1, Fig. 4).This section is separated by a fault of unknown (but probablysmall) throw from similar brown-grey siltstone cropping outon the shore platform. Siltstone, c. 5 m stratigraphicallybelow the fault, contains horizons with scattered fragmentsof calcareous sandstone and one large 0.6 m subroundedblock of calcareous sandstone containing angular chips ofWhangai-like siltstone. A dike of glauconitic sandstone,similar to the dikes in the shore platform at the mouth ofPukemuri Stream, cuts across Whangai strata a little lowerin the succession.

The upper portion of the Whangai Formation is wellexposed on the shore platform 1.2-1.5 km northeast of TeKaukau Point, where c. 18 m is exposed below a sharpcontact with the Manurewa Formation (Fig. 5). Most of theexposed succession consists of purplish brown-grey, veryfine sandstone. The sandstone is commonly finely laminated,and at a number of horizons hummocky cross-stratificationis present (Fig. 6). The lowest 8 m exposed includes a 3 mthick slumped unit containing dispersed blocks up to 3 m inlength, overlain by a better bedded succession which alsocontains scattered clasts. The clasts consist mainly of micriticlimestone, but calcareous sandstone, dark grey mudstone,conglomerate, and rare chert are also present. One 1 m blockof calcareous sandstone contains Inoceramus fragments. Thewell-bedded part of the clast-bearing succession includes a0.5-1 m bed of well-laminated, calcareous, fine sandstonewhich is hummocky cross-stratified in its upper part. Somelimestone and conglomerate clasts show evidence of softsediment injection and deformation. A horizon ofdiscontinuous lenses, up to 50 cm thick, of fine conglomerateenclosing scattered blocks of limestone and calcareoussandstone up to 50 cm in diameter (Fig. 7), is inferred to be

the remnants of a debris flow trapped in pockets or scourhollows in the soft substrate. Some lenses display basal loadcasting and overturned flame structures, which indicate aflow direction towards the east or southeast (Fig. 7).

The overlying 12 m of Whangai succession consist of"typical" purplish brown-grey siltstone and very finesandstone. The lower 6 m is strongly slump-folded and cutby a sandstone dike. The few fold axes measurable recordedmovement dominantly towards the southwest, with a minormode directed towards the southeast. Much of the remainderof the column contains hummocky cross-stratification. Theformation, which appears to be bioturbated in the topmostfew centimetres, is overlain sharply and with undulatorycontact by the Manurewa Formation.

Paleontology and ageThe oldest dinoflagellates from the Whangai Formation(f372) were collected from the base of the exposed sectionin Pukemuri Stream, which offers the thickest succession(Fig. 2). They have been assigned to the Vozzhennikoviaspinulosa Interval Subzone of Roncaglia & Schiøler (1997),making the age Early Haumurian (Crampton et al. 2000).This is based, firstly, on the joint presence of Satyrodiniumbengalense and Satyrodinium haumuriense, which have beenfound to co-occur only in the V. spinulosa Subzone, and,secondly, on the presence of Exochosphaeridium cf.phragmites, Chatangiella packhamii, Diconodiniumvitricornu, Odontochitina spinosa, and Senoniasphaeraedenensis, which also co-occur only in the V. spinulosa Zone.

The northernmost section (Manurewa Point) contains theoldest sample (f365, Fig. 4) from the eroded top of theWhangai Formation, immediately underlying the ManurewaFormation. It was assigned to Palaeocystodiniumgranulatum Interval Subzone of Roncaglia & Schiøler(1997) (Fig. 3), based on the co-occurrence of Manumiellaseymouriense and Palaeocystodinium golzowense combinedwith the absence of Odontochitina spp. and Manumielladruggii (Table 1). Thus, the age is mid Late Haumurian(Maastrichtian; Fig. 3).

At Pukemuri Stream, a sample (f373) from 10 cm belowthe top of the Whangai Formation yielded dinoflagellatesassigned to the Manumiella druggii Interval Zone of LateHaumurian (late Maastrichtian) age (Fig. 3), making ityounger than the top of the section at Manurewa Point. Thisdetermination was based on the presence of Manumiella sp. 1of Askin (1988), which has a joint first occurrence inAntarctica with M. druggii, the marker species for the M.druggii Zone, coupled with the absence of marker speciesfor subsequent (Paleocene) zones. The absence ofGlaphyrocysta spp. indicates that the sample is not from thetopmost part of the M. druggii Zone. Manumiella sp. 1 ofAskin (1988) is also present in the two samples (f377, f378)collected from the upper 18 m of the Whangai Formation inthe section northeast of Te Kaukau Point. The absence ofGlaphyrocysta spp. from both samples, the uppermost ofwhich was collected 20 cm below the top of the formation,suggests that here too the topmost part of the M. druggiiZone is missing, although palynomorphs are sparse in theupper sample (Table 1).

Thus, the dinoflagellates collected from the top of theWhangai Formation in the southern sections are youngerthan those from the Manurewa Point section to the north(Fig. 2). This is most likely due to the differing extent oferosion at the base of the Manurewa Formation.

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Table 1 Table showing sample and fossil record numbers, with dinoflagellates and acritarchs present in the samples collected from the Tora sections.

Field No.Fossil Record Form number S38/f...Laboratory No.

MP1 MP2 MP3 MP5 MP6 MP7 PS2 PS5365 366 367 368 369 370 371 372

L20100 L20101 L20334 L20102 L20103 L20104 L20087 L20088

PS20373

L20089

PS21374

L20090

ooo

PS22375

L20091

PS23376

L20092

O

PS24383

L20093

TKK1377

L20094

TKK3378

L20095

TKK4379

L20096

o

TKK6380

L20097

TKK7381

L20098

TKK8382

L20099

O

Alisocysta cf. margaritaAlisocysta sp. of Wilson, 1988bAlisocysta spp. (pars) O OAlterbidinium minus O OAmphidiadema rectangularisApectodinium homomorphum OAreoligera spp.Batiacasphaera kekerengensis OBatiacasphaera sp.Batiacasphaera subtilisCassidium fragile O cf.Chatangiella cf. packhamiiChatangiella packhamiiChlamydophorella discretaCirculodinium distinctum distinctum OCordosphaeridium fibrospinosumCordosphaeridium inodesCribroperidinium sp. of Marshall, 1990 OCribroperidinium spp. (pars)Cyclodictyon paradoxumCyclopsiella sp.Damassadinium cf. californicumDeflandrea medcalfii ODiconodinium vitricornuExochosphaeridium cf. phragmitesFibrocysta bipolaris OFibrocysta sp. OFibrocysta vectensisFromea chytra OFromea staveia OGlaphyrocysta marlboroughensisGlaphyrocysta retiintextaGlaphyrocysta sp. OGlaphyrocysta spp. (pars)Glaphyrocysta textaHafniasphaera septataHeterosphaeridium sp. of Schi0ler & Wilson, 1998 rewHystrichodinium cf. pulchrumHystrichostrogylon sp. of Schi0ler & Wilson, 1998Impagidinium sp. of Strong et al., 1995ImpagidiniumlPterodinium spp. (pars) OIsabelidinium cretaceumIsabelidinium marshalliiManumiella cf. druggiiManumiella lataManumiella seymouriense O

O

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Table 1 {continued)

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Manumiella sp. 1 of Askin, 1988Odontochitina costataloperculataOdontochitina cribropodaOdontochitina poriferaOdontochitina spinosaOligosphaeridium complexOligosphaeridium pulcherrimumPalaeocystodinium golzowensePalaeocystodinium granulatumPalaeocystodinium rhomboidesPalaeohystrichophora infusorioidesPalaeoperidinium pyrophorumParalecaniella indentataPhelodinium magnificumPyxidinopsis sp.Satyrodinium bengalenseSatyrodinium cf. bengalense (with apical horn)Satyrodinium cf. haumuriense (with apical horn)Satyrodinium haumurienseSenoniasphaera edenensisSpiniferites pseudoforcatus pseudofurcatusSpiniferites ramosus ramosusSpiniferites ramosus reticulatusTanyosphaeridium xanthiopyxidesTrichodinium sp.Trithyrodinium evittiiTurbiosphaera filosaVozzhennikovia spinulosaXenascus ceratioidesXenikoon sp. A of Foucher & Robaszynski, 1977

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O = present • = abundant rew = presumed reworked

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Block 4

Block 3

WESTERN BLOCKS

AwheaFormation

5f370

iSHW

Manurewa Formation(Lower Member)

Block 5

f369

• ' . ' .' I}

ManurewaFormation

(Lower Member)

EASTERN BLOCKS

f366f365 Whangai Formation

Fig. 4 Stratigraphic columns through Whangai, Manurewa, and Awhea Formations in structurally offset blocks at Manurewa Point,showing lateral lithofacies variations. "f" numbers used in this figure, Fig. 5, and in the text refer to fossils collected from Topographicmap 260, S28 Palliser. See Fig. 2 for legend.


The common presence of well-developed hummocky cross-stratification, at least in the uppermost part of the succession,suggests that deposition of this portion was above stormwave base (i.e., mid-shelf depths or shallower; Harms et al.1975). Beds of very fine to fine sandstone with scatteredmegaclasts up to 3 m in diameter are probably olistostromesthat have slumped into place down a slope. This is supportedby the presence of slump folding in the beds associated with,or contiguous to, the olistostromes, which also suggestdownslope movement. Inoceramids have so far not beenpositively identified from the Haumurian Stage in NewZealand (Crampton 1996), so the presence of fragments ofthe bivalve Inoceramus in a block within an olistostromesuggests that an area of older Cretaceous strata had been atleast locally uplifted and was acting as a source duringHaumurian times. The origin of the limestone clasts has notbeen determined.

The sediments are therefore inferred to have beendeposited in depths equivalent to moderately shallow shelf,on a seafloor swept by frequent storms. Periodic tectonicactivity was also likely, as indicated by the presence ofolistostromes containing exotic blocks, including clastscontaining pre-Haumurian fossils.

Manurewa FormationDescription

The lithologically complex Manurewa Formation wasdefined by Waterhouse & Bradley (1957) as "a sequenceabout 100 ft thick of limestone, greensand and marls... lyingbetween the Whangai and Awhea Formations". PukemuriStream was designated as the type section, although thesections examined at Manurewa Point and northeast of TeKaukau Point (Fig. 1) are better exposed and show clearercontact relationships with adjacent units. At all threelocalities the Manurewa Formation rests with sharp contacton the underlying Whangai Formation; this is clearly anerosional contact in the case of Pukemuri Stream. Mostcontacts with the overlying Awhea Formation aregradational. The three sections examined differ somewhatin character.

Manurewa Formation is well exposed in low cliffsbordered by a shore platform at Manurewa Point. The sectionis transected by many subvertical normal faults of small (c.1-4 m) throw, which divide the outcrop into a succession ofslightly offset structural blocks (Fig. 4). Correlation betweenblocks can generally be carried out by using scattered thinlimestone or conglomerate layers, although it was notpossible to correlate precisely between the western and

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Fig. 5 Stratigraphic column from section northeast of Te KaukauPoint, showing lithofacies and sedimentary features in theWhangai, Manurewa, and Awhea Formations. See Fig. 2 for legend.

eastern ends of the outcrop because of the presence of a largerfault where overlap could not be established. However, basedon lithological relationships, the thickness of missing stratais unlikely to be more than a few metres and is probablymuch less. The total thickness of the Manurewa Formation

at Manurewa Point is between c. 15 and 19 m. The base ofthe formation is exposed at the western end of the point(block 1, Fig. 4), where it rests sharply on the WhangaiFormation. The sharp upper contact with the overlyingAwhea Formation is exposed at the eastern end of the point(block 4, Fig. 4).

The westernmost structural block (block 1, Fig. 4)includes the sharp irregular contact with underlying WhangaiFormation, and a total thickness of 9 m is represented beforethe upper portion is obscured (block 2, Fig. 4). The westernblocks (blocks 1 and 2, Fig. 4) are dominated by regularlybedded, sharp-based, very fine calcareous sandstone withbed thicknesses averaging between 15 and 20 cm, and up to50 cm in thickness, separated by layers of siltstone up to 2cm thick (Fig. 8). The sandstones are poorly sorted,consisting of angular to subangular quartz grains andscattered grains of glauconite in a calcitic matrix. The thickersandstone beds show internal lamination, commonly parallel,and less commonly cross-lamination or ripples. Althoughgrading is not apparent in most beds, a single 50 cm thickbed 1.3 m above the basal contact is sharp based, gradingupwards from fine to very fine sandstone. Feeding traces oforganisms are common on the exposed surfaces of mostsandstone beds.

The western structural blocks can be correlated with eachother by following a bed of highly calcareous, very finesandstone to micritic limestone, between 5 and 10 cm thickand thickening eastwards, located 1.8 m above the base ofthe Manurewa Formation (Fig. 4, 8). This bed disappears tothe west, where it is channelled into by a 10 cm thick, clast-supported granule conglomerate, but can be traced eastwardsacross several small faults. Organic feeding traces are prolificon the surface of the calcareous bed, and burrows arescattered throughout. A thicker (95 cm) clast-supportedgranule conglomerate occurs 4 m above the base of theformation. It has sharp contacts at base and top, and includessmall clasts of deformed purplish brown-grey mudstone,inferred to be rip-up clasts of Whangai Formation. A smalllens of similar conglomerate occurs 1.5 m higher up thesuccession.

Fig. 6 Well-developed hum-mocky cross-stratification in veryfine sandstones of the WhangaiFormation; section on shoreplatform northeast of Te KaukauPoint. Hammer for scale.

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Fig. 7 Debris flow deposits inthe Whangai Formation, sectionnortheast of Te Kaukau Point.Note the large (50 cm) clast oflimestone behind the hammerhead, and clast of calcareoussandstone to its left. Loads andflame structures are developed inthe underlying mudstone/very finesandstone, overturned to the left,indicating an east-southeastdirection of flow.

Fig. 8 Alternating thin sandstoneand mudstone beds, offset bysmall faults, of the LowerMember, Manurewa Formation,Manurewa Point. The hammerhead rests on a 5-10 cm bed ofmicritic limestone.

The eastern blocks (blocks 3-5, Fig. 4) east of the largerfault contain nearly 8 m of similar alternating calcareoussandstone and thin mudstone beds, commonly with parallelor cross-lamination, and with scattered thin conglomeratehorizons and rare thin limestone beds. Bioturbation isextremely common in most beds. A 20 cm thick sandstonenear the middle of the succession is slightly glauconitic andcontains current ripples, possibly wave modified. Theeasternmost fault block (block 5, Fig. 4) contains 70 cm ofslump-folded fine sandstone and thin granule conglomerate.The axis of slump folds and direction of overturning of bedssuggests movement towards the southeast. This is overlainby alternating sandstone and mudstone beds cut by a channel,up to 70 cm deep, c. 4 m below the upper contact of thesuccession. It is infilled with slurried and slumped layers of

Whangai-like brown-grey mudstone and thin, elongated, andcontorted, highly calcareous sandstone clasts up to 20 cmin length. The infill thins westwards and the channeldisappears within a few metres. The alternating successionis capped by a bed of micritic to sandy limestone 30—40 cmthick and burrowed throughout. The burrows penetrate upto 50 cm below the base of the limestone into the underlyingsandstone, which also contains scattered granule-sizedrounded clasts of dark sandstone.

The top of the limestone bed, which is exposed only inthe eastern structural blocks, is an erosion surface, overlainby coarse siliciclastic deposits which vary in nature fromwest to east (Fig. 4, 9). In the westernmost exposure (block3, Fig. 4), the limestone is sharply and erosively overlainby the lowest of three thick, graded conglomerate to

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Fig. 9 Greensand of the UpperMember, Manurewa Formation,overlying limestone of the LowerMember, Manurewa Formation,Manurewa Point. The hammerhead rests on a burrowed erosionsurface between the twolithologies.

Fig. 10 Olistostrome with blocksof limestone and WhangaiFormation dark siltstone/very finesandstone (outlined to right oflarge limestone block) in a matrixof glauconitic medium to coarsesandstone, Upper Member,Manurewa Formation, ManurewaPoint. Lens cap (lower left centre)for scale.

sandstone beds totalling c. 2 m in thickness. The beds rangein thickness from 40 cm to 1 m, and have basal granule topebble conglomerate grading upwards into bioturbatedmedium to fine sandstone. The topmost, 1 m thick bed iscontent graded, with pebble-sized clasts at the base gradingupwards into medium sandstone with dispersed granules.The bed lacks bioturbation, is slightly glauconitic, and isinternally laminated, with an interval at the top with low-angle cross-stratification.

The top of the coarse deposits is also an erosion surface,overlain by conglomerate consisting of sandstone withscattered clasts, ranging from granules to megaclasts 1 m indiameter (Fig. 10). The erosion surface underlying theconglomerate cuts into successively lower beds to the east,eroding through the underlying coarse deposits to thelimestone, and then through the limestone to the top of thealternating sandstone succession in the easternmost outcrops.The megaclast-containing unit varies in appearancethroughout its c. 15 m of lateral exposure. The matrix

consists of moderately sorted greenish medium to coarsesandstone, consisting of subangular to subrounded quartzgrains, with a subordinate component of glauconite. Thesupported clasts consist of sandstone, mudstone, andlimestone, mainly from pebble to cobble size, but with largerirregular blocks up to 1 m. The megaclasts are dominantlyof burrowed limestone similar to the underlying eroded bed,and of purplish-brown siltstone similar to WhangaiFormation. The Whangai clasts commonly show soft-sediment deformation, suggesting that they were only partlyconsolidated when eroded. The conglomerate is overlainsharply by the regular-bedded fine-grained sandstones of theAwhea Formation (block 4, Fig. 4).

At Pukemuri Stream, 4 km to the southwest of ManurewaPoint (Fig. 1, 2), the top of the Whangai Formation istruncated by an erosion surface with a relief of at least 0.5 m.At stream level this is overlain by 50 cm of muddy limestone,massive at the base but laminated at the top. Burrows andfeeding traces occur throughout. A thin layer of very fine

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grained sandstone separates this unit from 1 m of thinlybedded calcareous mudstone. This in turn is overlain by threethick beds of calcareous fine-grained sandstone up to 1.5 m.

Overlying the calcareous sandstone with a sharp contactis 3 m of massive, green, slightly glauconitic sandstone,which in turn is overlain sharply by a heavily veined breccia-conglomerate 2.5 m thick with blocks up to 50 cm indiameter. The largest blocks consist of limestone, withsmaller more rounded clasts of sandstone and chert. Thebreccia-conglomerate is separated by a sharp, irregularsurface from overlying massive, moderately well sorted,medium-grained, greenish sandstone consisting pre-dominantly of subangular quartz grains with subordinateglauconite. This passes upwards gradationally within 5 minto thin-bedded, blue-grey, very fine grained sandstone ofthe Awhea Formation (Fig. 2). The total thickness ofManurewa Formation at Pukemuri Stream is c. 11 m.

In the section northeast of Te Kaukau Point (Fig. 1, 5),Manurewa Formation overlies the Whangai Formation withsharp and undulatory (probably scoured) contact. The basalbed is a thin (8 cm) layer of very coarse sandstone, which isin turn sharply overlain by a mainly fine sandstone unit 5.2 mthick. The basal 30 cm of this unit comprises mediumsandstone containing scattered granules and small rip-upclasts of siltstone and fine-grained, slightly glauconiticsandstone. This passes upwards gradationally into well-laminated, fine quartzose sandstone, with slightly divergentlaminae and local burrowed horizons.

Similar medium to fine sandstone beds, locally slightlyglauconitic and averaging from 60 cm to 2.8 m thick, formthe bulk of the remainder of the formation. They arecommonly strongly internally laminated, and, particularlyin the upper half of the unit, are convoluted and show water-escape structures near the tops of beds. Tops are alsocommonly burrowed.

Two beds of micritic limestone, 20 and 10 cm thick, thelower one with a highly burrowed base, are interspersed withsandstones 5.3 and 10.5 m above the base of the ManurewaFormation northeast of Te Kaukau Point (Fig. 5). Midwaybetween the two limestone beds are two contiguous beds ofmatrix-supported conglomerate—the lower 30 cm thick andthe upper 2.5 m thick. The basal contacts of both beds aresharp and erosive, and the units are dominated by fine tomedium-grained sandstone with scattered clasts. In the lowerbed, clasts are mainly of granule to pebble size and consistof sandstone and mudstone, with two outsize blocks oflimestone up to 1 m long, one protruding from the top ofthe bed. The unit is probably lenticular, as it thins anddisappears laterally. The upper conglomerate bed, consistingmainly of massive, fine-grained sandstone, contains scatteredclasts of limestone up to 15 cm in diameter in the upperone-third of the bed.

The base of the overlying Awhea Formation northeastof Te Kaukau Point is taken arbitrarily as coinciding withthe change from beds containing convolutions and water-escape structures in their upper layers, to the beginning of asuccession of sandstones with prominent low-angle cross-stratification (Fig. 5).

At Manurewa Point and in Pukemuri Stream, theManurewa Formation can be subdivided into two separatemembers (here designated the Lower and Upper Members)with distinct characteristics, separated by an erosion surface.The Lower Member is erosive into the underlying WhangaiFormation, and is composed dominantly of calcareous or

fine to very fine grained clastic deposits. The Upper Member,which rests on an erosion surface cut into the Lower Member,is dominated by glauconitic medium sandstone andolistostromes.


Manurewa Formation consists of a complex of units ofdifferent ages, spanning the K/T boundary. The oldestcomponent is the Lower Member, which is represented atManurewa Point and Pukemuri Stream, where it erodes intoWhangai Formation.

The Lower Member at Manurewa Point revealed amismatch between data from dinoflagellates andforaminifera. Two dinoflagellate samples (f366, f367, Fig.4), one from a few centimetres above the base and the other1.8 m above the base of the unit, were assigned to theApectodinium homomorphum Interval Zone of Wilson(1988a), based on the presence of A. homomorphum in thelower sample and on the presence of Impagidinium sp. ofStrong et al. (1995), Cassidium fragile, and Alisocysta sp.of Wilson (1988b) in the upper sample. This equates to alate Teurian to early Waipawan (late Paleocene) age.

However, a foraminiferal sample (f358) fromstratigraphically between the two dinoflagellate samplescontains Heterohelix globulosa, Rugoglobigerina cf.pustulata, Rugoglobigerina sp., and possible specimens ofHedbergella monmouthensis, all of which give a LateHaumurian age. In addition, dinoflagellates from a sample(f368) 1.4 m below the top of the unit exposed to the east ofthe fault, and stratigraphically higher than the samples above,belong to the Manumiella druggii Interval Zone of Helby etal. (1987), and therefore are Late Haumurian (lateMaastrichtian; Fig. 3). This determination was based on thepresence of Cassidium fragile, Fibrocysta spp.,Palaeoperidinium pyrophorum, and M. seymourense,coupled with the absence of Odontochitina spp.

There is, thus, a conflict in age assessment. However,the stratigraphy of the unit argues for a position betweenthe Late Cretaceous P. granulatum Interval Zone and theearliest Paleocene T. evittii Interval Zone. As theforaminiferal data clearly point to a Haumurian age for theLower Member of the Manurewa Formation, the presenceof late Teurian to early Waipawan dinoflagellates isconsidered to be the result of contamination from sedimentsabove. A Late Haumurian (late Maastrichtian) age istherefore adopted.

The Lower Member of the Manurewa Formation inPukemuri Stream is assigned to the uppermost part of theManumiella druggii Interval Zone based on the presence ofDamassadinium cf. californicum, Glaphyrocysta retiintexta,Impagidinium sp. of Strong et al. (1995), Turbiosphaerafilosa, Fibrocysta bipolaris, Fibrocysta vectensis, andAlisocysta sp. of Wilson (1988b) (Table 1). The age is thuslatest Haumurian (latest Maastrichtian) (Fig. 3).

The Upper Member of the Manurewa Formation sharesmore lithological characteristics in common between thethree described sections. At Manurewa Point, the onlysample collected from the upper part of the ManurewaFormation was assigned to the Palaeocystodiniumgranulatum Interval Subzone on the basis of the presenceof Manumiella seymouriense and the absence ofOdontochitina spp. and M. druggii s.s. This Late Haumurian(early late Maastrichtian) age is clearly anomalous as theunit from which it was collected is underlain by strata

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containing younger Haumurian dinoflagellates, and it isoverlain by strata containing Teurian (Paleocene) microflora(see later). The sample was collected from a sandstonecontaining megaclasts from older strata, and the flora areinferred to have been reworked. On lithological grounds,the Upper Member of the Manurewa Formation here is likelyto be the same age as that at Pukemuri Stream, where thelithologies are similar.

In the Pukemuri Stream section, a sample from thegreensand below the conglomerate proved to be barren, buta sample from greensand immediately above theconglomerate contained T. evittii, and was therefore assignedto the T. evittii Range Zone which is earliest Teurian (earliestPaleocene).

At the section northeast of Te Kaukau Point, the onlyage-diagnostic dinoflagellates came from a sample (f379,Fig. 5) collected from 30 cm above the base of the unit: theother samples were either barren or lacking age-diagnosticdinoflagellates. The productive sample containedTrithyrodinium evitii, and is assigned to the T. evittii RangeZone of Wilson (1987) of earliest Teurian (earliestPaleocene) age. Only the Upper Member of the ManurewaFormation is present northeast of Te Kaukau Point. Theapparent absence of the uppermost Cretaceous here, and theprobable erosional contact of the Whangai Formation withthe overlying Upper Member of the Manurewa Formation,suggests that an uncertain thickness of strata, possiblyincluding originally deposited strata of the Lower Member,has been removed by erosion. An uplifted and eroding LowerMember may have provided the source of the ubiquitousclasts of limestone in the Upper Member olistostromes.

Manurewa Formation thus ranges in age from lateHaumurian to early Teurian (late Maastrichtian to earlyPaleocene), and straddles the K/T boundary.


The rapid facies and thickness changes between theManurewa Point and Pukemuri Stream localities, the absenceof the Lower Member from the locality northeast of TeKaukau Point, and the erosional nature of the basal contactat Pukemuri Stream, suggest that the lower unit infills achannel eroded into the Whangai Formation. This is furthersupported by the presence of a small channel within thesuccession at Manurewa Point.

The environment during channel infill appears to havebeen relatively quiet, as evidenced by generally fine graineddeposition, including that of muddy limestone, alternatingwith sporadic bursts of turbidity current activity indicatedby rare graded beds and cross-lamination. The benthicforaminiferal assemblage from near the base of the LowerMember at Manurewa Point (f358, Fig. 4) contains amoderately calcareous and agglutinated fauna, includingMatanzia varians, Stensioina beccariiformis, Glomospiracharoides, and Hyperammina sp., suggesting that thepaleodepth was bathyal. If the bathyal depth suggested bythe foraminifera is correct, it contrasts with the mid-shelfdepth inferred for the underlying Whangai Formation, andindicates a relative sea-level rise between the two units.

The Upper Member of Manurewa Formation is presentin all three sections examined, but although the two northernlocalities share similar lithologies, the only lithology incommon with the southern locality is a conglomerate unitconsisting of sandstone matrix supporting megaclasts mainlyof limestone. The presence of beds containing megaclasts,

some with soft-sediment deformation, in all three sections,suggests that the units were emplaced as olistostromes. Theolistostrome is separated from the deposition of theunderlying sandstone, at least at Manurewa Point, by a clearerosional base. The erosion surface cuts down successivelythrough greensand and then into the underlying cappinglimestone of the lower unit (Fig. 9). The Upper Member ofManurewa Formation is not only erosive into the LowerMember, but also contains erosion surfaces within it. As withthe Lower Member, the Upper Member probably alsorepresents a channel system.

At both Manurewa Point and Pukemuri Stream, thechannel infill is greensand, separated from the LowerMember by the erosion surface. At Pukemuri Stream, thegreensand appears massive, but at Manurewa Point thick,graded granule to sandstone beds are bioturbated withvertical burrows, and locally have low-angle cross-stratification. Deposition in an active, probably shallowmarine environment seems likely. In the succession northeastof Te Kaukau Point, some beds in the Upper Member ofManurewa Formation showing normal grading, basalerosion, and water-escape structures may have beenemplaced by sediment gravity flows, as were theolistostrome horizons. This suggests that the seafloor hadsufficient slope to generate such gravity flows.

The shallow water interpretation is supported by theabundant presence of the acritarch Paralecaniellaindentata—an indicator of a low-salinity, probably marginalmarine environment (Brinkhuis & Schiøler 1996; Schiøleret al. 1997)—in greensand directly above the olistostromein Pukemuri Stream. It also occurs immediately above thebase of the Manurewa Formation northeast of Te KaukauPoint.

The sample (f379, Fig. 4) from the base of the UpperMember of the Manurewa Formation exposed northeast ofTe Kaukau Point contains, in addition to the presence ofprobably marginal marine P. indentata, common fungalhyphae and fungal spores, whereas virtually none occur inthe immediately underlying Whangai Formation. Most fungihave a non-marine origin, and their abundance in the UpperMember of Manurewa Formation suggests a more nearshoresetting than for the Whangai Formation. In addition, thepresence of many ruptured cysts in this sample, comparedwith their absence or near absence in the underlying WhangaiFormation, also suggests a more turbulent, probablynearshore environment.

The lateral extent of the Manurewa channel complex isunknown. Its orientation is uncertain, the only directionalfeature recorded being a slump fold in the succession atManurewa Point, indicating movement towards thesoutheast. If this is parallel with the channel margin, achannel width of at least 4 km is implied for the LowerMember. The width of the channel infilled by the UpperMember is likely to have been in excess of 9 km. The outcroppasses out to sea to the southwest and to the northeast of theTora area, and the nearest correlative strata to the northeastcrop out in the Glenburn-Flat Point area to the northeast. Asection comparable in age to that at Tora, and located 35km to the northeast in Huatokitoki Stream (Fig. 1) nearGlenburn, was described by Lee (1995), but no stratigraphicbreaks were recorded in an apparently gradational successionfrom Haumurian (Maastrichtian) into Teurian (earlyPaleocene) strata. Massive recent landslips have coveredmost of the critical section since Lee's studies, so we were

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Fig. 11 Successive beds of well-sorted fine sandstone with low-angle cross-stratification. AwheaFormation, northeast of TeKaukau Point. Hammer for scale.

unable to field check that data.Together, the two members appear to form a major,

nested channel complex. The notably coarse nature of theUpper Member of the Manurewa Formation in all threelocalities, and its probable shallow water environmentcompared with the underlying inferred bathyal LowerMember or finer grained Whangai Formation, suggests abasinward shift of shoreline at, or just above, the K/Tboundary, because of either increased sediment supply orrelative drop in sea level.

Awhea FormationDescription

Only the lower few metres of the Awhea Formation wereexamined in order to establish the nature of the contact withthe underlying Manurewa Formation. The contact betweenthe two units is either gradational or erosive, depending onlocality. At Manurewa Point the contact is sharp and highlyburrowed, suggesting a hiatus (block 4, Fig. 4). Theoverlying succession consists of very regularly bedded,highly bioturbated, fine sandstones, commonly parallel-laminated throughout. The sandstones are poorly tomoderately well sorted, and consist of subrounded quartzgrains. Average bedding thickness is 5-10 cm.

AtPukemuri Stream, glauconitic sandstone of ManurewaFormation grades up over a few metres into alternatingcalcareous, very fine sandstone and thin mudstone interbedsof Awhea Formation. The beds have similar characteristicsto those at Manurewa Point, but here the quartzosesandstones are noticeably glauconitic and calcareous.

In the coastal section northeast of Te Kaukau Point, thepresumed contact is marked by a discontinuous erosionsurface distinguished by an irregular layer of granules atthe base of a 2.8 m thick bed containing low-angle cross-stratification in its upper half. Concave-upward depressionsup to 0.5 m deep eroded into the upper surface of the bedare infilled by draped laminated sandstone. The succeedingbeds consist largely of non-glauconitic well-sorted quartzosefine sandstone between 25 and 70 cm thick, well laminatedbut highly bioturbated, and with common low-angle planar

cross-stratification (Fig. 11). The contact between formationsis most clearly observed as the change from beds withconvolutions and water-escape structures to the beginningof a succession of thinner beds with low-angle cross-stratification, as the erosion surface is discontinuous (Fig.2,5).


The oldest sample identified came from c. 50 cm above thebase of the formation at Manurewa Point (f370, Fig. 4). Itwas assigned to the Palaeocystodinium golzowense IntervalZone of Wilson (1984, 1988a), based on the presence ofdinoflagellates Deflandrea medcalfi and Turbiosphaerafilosa, and the absence of M. druggii, T. evittii, andApectodinium homomorphum. The age of the basal part ofthe Awhea Formation in this section is thus early-late Teurian(early-late Paleocene).

A sample (f382, Fig. 5) from c. 4 m above the base ofthe formation at the locality northeast of Te Kaukau Pointwas assigned to the lower to middle part of the Apectodiniumhomomorphum Interval Zone, based on the presence ofCordosphaeridium fibrospinosum and Glaphyrocysta texta,and the absence of marker species of zones above the A.homomorphum Zone. The age of this sample is thus lateTeurian to early Waipawan (late Paleocene to early Eocene).

No zonal assignment was possible for a sample (f383)from c. 10 m above the olistostrome in Pukemuri Stream,but it can be assigned a broad latest Haumurian-Waipawan(latest Maastrichtian to early Eocene) age based on thepresence of the dinoflagellate Fibrocysta cf. bipolaris.

The lower part of the Awhea Formation thus falls withinthe range early Teurian to early Waipawan (early Paleoceneto early Eocene) age.


The highly bioturbated nature of the deposits, and thecommon occurrence of low-angle cross-stratification in thesection northeast of Te Kaukau Point, indicates very shallowmarine, probably nearshore deposition. The thick, well-sorted beds suggest considerable wave or current activity.

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The concave-upward depressions at the base of the unit arepossibly the result of scouring by waves, which is compatiblewith a nearshore, shallow marine environment. Theconcentration of shallow water indicators in thesouthwesternmost outcrop may indicate shallowing in thisdirection. The abundant presence of the acritarchP. indentatain the sections at Pukemuri Stream and northeast of TeKaukau Point also indicates deposition in a marginal marine,possibly shallow water, low-salinity environment (seeearlier). The environment is shallower than that interpretedfor the Upper Member of the Manurewa Formation, andindicates continued marine regression.

DISCUSSION

Environment of deposition and relative sea-levelchangesThe paleoenvironment from Late Cretaceous throughPaleocene times was entirely marine along what is now theWairarapa coast. The sediments appear to have beenemplaced mainly in the equivalent of mid to shallow shelfdepths, up to nearshore marine in the late Paleocene.

Although the Piripauan (Santonian) Glenburn Formationconsists dominantly of turbidites, the presence of scours,scattered horizons of large-scale cross-stratification, and ofpossible storm wave formed structures, suggest a shelfenvironment, periodically swept by strong bottom currentsand/or storm waves. The high degree of bioturbation,including burrows of suspension feeders, supports aninterpretation of deposition at shelf depths above storm wavebase.

The succeeding Haumurian (late Santonian-Maastrichtian) Whangai Formation, although finer grained,has prominent horizons of hummocky bedding, whichstrongly suggest storm wave influence at shelf depths. Thepresence of slump horizons and of debris flows, perhapschannelled, suggests a slope to the floor of the depositionalbasin. The fine grain size is typical of the Whangai Formationelsewhere on the east coast of New Zealand, and is inferredto record marine transgression resulting from thermalsubsidence of the New Zealand landmass accompanying itsseparation from Gondwana at c. 85 Ma (Crampton et al.1999).

The Late Cretaceous, Lower Member of the ManurewaFormation channel system is infilled by mainly fine grainedsediments, typically fine to very fine sandstone beds,mudstone, and limestone. Rare thin-bedded sandstones aregraded and may represent turbidites. Scattered fineconglomerates, one of which infills a local channel, probablyalso represent sediment gravity flows. The absence of large-scale traction current features and of hummocky cross-stratification in contrast to its prominence in the underlyingWhangai Formation, suggests a low-energy environment ofdeposition deeper than storm wave base. This depthinference is supported by the benthic foraminiferalassemblage, which suggests that the paleodepth was likelyto be bathyal. Therefore, the Lower Member of theManurewa Formation records a relative sea-level rise.

The early Paleocene, Upper Member of ManurewaFormation is strikingly different from the lower unit. Itsgenerally coarser nature and good sorting suggest an activeshelf environment above storm wave base. This is supportedby the abundant presence locally of the acritarch

Paralecaniella indentata, of common fungal material, andof other indicators which suggest a marginal marine, possiblyshallow water environment. These strongly suggest a relativesea-level fall and a basinwards shift of shoreline,accompanied by widespread shallow marine conditions.

The lower, early-late Paleocene part of Awhea Formationwas deposited in a shallow marine environment,considerably closer to shoreline than the underlyingManurewa Formation. The occurrence of thicker, coarsersandstone beds, common presence of horizons of low-angletrough cross-stratification, and probable wave-scouredtroughs at the section northeast of Te Kaukau Point, suggestthat this was shallower and much nearer shore than thesections to the northeast.

The evidence therefore suggests that there was a majortransgression, accompanied by channelling, in the latestCretaceous, followed in the earliest Paleocene by rapidregression, which continued into the late Paleocene, resultinglocally in nearshore environments.

Tectonic environmentThe Upper Haumurian to lower Teurian (upper Maastrichtianto lower Paleocene) succession along the Tora coast containsa record of frequent mass sediment movement (slumpingand olistostrome emplacement) which does not relate closelyto deposits in correlative strata in the surrounding region.This activity could relate to local tectonism, or possibly toemplacement on, or at the foot of, a contemporary submarineslope of sufficient steepness to generate sediment massmovement.

Seismically induced shaking or large slumping eventscan trigger sedimentary intrusions into non-lithifiedsediments (e.g., Hiscott 1979; Plint 1985; Rowe et al. 2002),and may have caused injection of the sandstone dikes intothe Whangai Formation. Browne (1987) inferred thatsedimentary dikes intruding the younger late Paleocene toearly Eocene Mungaroa Limestone at Te Kaukau Pointpostdated lithification and folding, and were possibly relatedto latest Eocene or early Oligocene deformation. However,the sandstone dikes intruding the Whangai sediments,although present throughout much of the formation,including the youngest portion, do not appear to affect theoverlying Manurewa Formation. They are thus likely to besyndepositional or immediately postdepositional, and maybe associated with downslope movement, perhapsseismically induced, causing both large-scale slumping andextension fissures, mainly parallel to slope, which facilitateddike intrusion. The northeast trend of the majority of thedikes, coupled with sparse paleocurrent determinations (seeearlier), may indicate that the seafloor sloped towards thesoutheast. Conflicting evidence comes from slump folds,which suggest both southeast and southwest directions ofmovement.

Seismically induced shaking can also initiate downslopedensity currents. The occurrence of Inoceramus-bearingsandstone clasts in Whangai Formation olistostromessuggests that Glenburn Formation or older strata were beingexposed and eroded in late Whangai (latest Cretaceous)times. Similarly, inclusion of outsize clasts of LateCretaceous Whangai Formation in the lower Paleoceneolistostrome of the Upper Member of Manurewa Formationat Manurewa Point indicates that local erosion of older stratawas also occurring in early Paleocene times. The most likelyexplanation is that in each case this was due to uplift along

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an active fault or faults, or on growing folds. Tectonic activityin the latest Cretaceous and earliest Paleocene may also havebeen responsible for generating slumps and olistostromes,with seismic activity triggering the mass flows. The presenceof a large and apparently long-lived channel system spanningthe K/T boundary may also be related to erosion caused bycontinuing local tectonic activity. Associated subsidencecould have been responsible for relative sea-level rise andtransgression in the lower unit of the Manurewa Formation.

New Zealand was supposedly in a passive margintectonic setting during Late Cretaceous and Paleocene times(Bradshaw 1991), a situation in which tectonic activity ingeneral is considered to be anomalous. However, activefaulting during the Haumurian has been documented on theWest Coast of the South Island (Laird 1993, 1994) and inNorth Canterbury (Nicol 1993). Moore (1980) also inferredactivity on the Adams Fault and possibly other faults to thenorth of the Tora area in the Late Cretaceous. Strata ofPiripauan to Early Haumurian age near Ngahape, 60 kmnortheast of Tora, show evidence of penecontemporaneousfaulting, supported by the presence elsewhere in thesuccession of coarse breccias containing large blocks of olderstrata (Moore 1980). Consequently, the inferred tectonicactivity at Tora during at least the Late Cretaceous iscorrelative with tectonic activity elsewhere in New Zealand,but does not fit the passive margin tectonic model.

Comparison with other K/T boundary successions inthe East Coast BasinThe Tora K/T boundary succession occupies a geographicalposition between the well-studied, lithologically verydifferent coeval successions of Marlborough to the southand Hawke's Bay to the north (Fig. 1). With layers oflimestone and calcareous sandstone and mudstoneintercalated within the dominantly clastic ManurewaFormation, the succession at Tora appears to represent atransition between the clastic Hawke's Bay sections and thecoeval mainly calcareous eastern Marlborough strata.

In Marlborough, the K/T boundary occurs within thecalcareous/siliceous Mead Hill Formation, and is markedby a distinct lithologic change which separates latestCretaceous thick-bedded moderately siliceous limestonefrom earliest Paleocene thin-bedded calcareous chert (Holliset al. 2003a,b, this issue). The K/T boundary successionappears to be incomplete in sections in the northern ClarenceValley, a situation attributed to erosion following asignificant sea level fall (Hollis et al. 2003a). In easternMarlborough, although locally there is a hiatus and impliederosion at the K/T boundary, there is no compelling evidencefor a significant fall in sea level (Hollis et al. 2003b),although this would be less apparent in the bathyalpaleoenvironment prevailing here than in the shallowermarine situation of the northern Clarence valley (Hollis etal. 2003a,b). In the eastern sections, the contrastingCretaceous and Paleocene lithologies are separated by a thinclay layer which bears the characteristic geochemicalsignature of K/T boundary clays (references in Hollis &Wilson 2000). The calcareous strata, which extend forbetween c. 14 and 60 m below the K/T boundary in easternMarlborough, pass downwards with rapid transition into darkgrey Whangai-equivalent siltstone, or, in the Ward coastalarea (Fig. 1), into fine turbidite sandstone (Price 1974; Strong2000). The interbedded limestone and calcareous sandstoneof the Lower Member of the Manurewa Formation at Tora

Fig. 12 Palinspastic reconstruction of central New Zealand atabout the K/T boundary (65 Ma), showing relationships andcontrasting paleoenvironmental settings of successions at Tora,Hawke's Bay, and Marlborough. The modern-day New Zealandmargin is shown as a bold line. Modified from Crampton et al.(2003, this issue).

may be a lithological equivalent. However, foraminiferaindicate that the paleoenvironmental setting in Marlboroughranged from outermost shelf to mid-bathyal in the latestCretaceous (Strong 1977, 2000; Hollis 1996; Hollis et al.2003a), a deeper environment than at Tora (Fig. 12).

In Hawke's Bay, eastern North Island, the K/T boundarycommonly lies within the fine-grained clastic WhangaiFormation, which extends in age from Early Haumurian toearly Teurian. In at least two localities, at Tawanui, inSouthern Hawke's Bay (Wilson et al. 1989), and in the TeHoe River area, western Hawke's Bay (Wilson & Moore1988) (Fig. 1), where dinoflagellate biostratigraphy has beenwell established, the K/T boundary is marked by adisconformity. At both localities the uppermost portion ofthe latest Cretaceous M. druggii Zone is absent, suggestingthat the upper part of the underlying succession has beenremoved by erosion. At other localities there is either noclear erosional break, or an erosional break is present butpoorly constrained paleontologically (Moore 1989a).

A temporary increase in sand content occurs above theboundary, suggesting a lowering of relative sea level (Moore1989a; Wilson et al. 1989). At Tawanui, this inference isfurther supported by an increase in spore/pollen abundancein overlying sediments, suggesting a basinward shift ofshoreline across the K/T boundary (Wilson et al. 1989). Theincrease in sand above the boundary is commonlyaccompanied by an increase in glauconite and carbonatecontent, the former of which is also a notable feature acrossthe K/T boundary at Tora.

The comparison between the K/T boundary successionat Tora and those of Hawke's Bay and Marlborough iscomplicated by the inferred paleogeographic setting (Fig. 12).

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The Tora area is inferred to lie in shallow water much closerto a shoreline than the other localities discussed, while itsclosest neighbours (Tawanui, Ward, and northern Clarencevalley) were likely to be experiencing bathyal to outer neriticconditions.

In general, conglomerates and other coarse clastic unitsare uncommon in the Whangai Formation and Whangaiequivalents, and sedimentary breccias with outsize clasts areextremely rare (Moore 1988b). The only major breccia unitrecorded so far from Whangai Formation of Late Cretaceousage is the Kirk's Breccia Member, which forms the lower(Late Piripauan to Early Haumurian) portion of the formationat Kirk's Clearing, western Raukumara Peninsula (Moore1989b) (Fig. 1). The breccia consists of mainly pebble tocobble-sized clasts of Whangai and pre-Whangai mudstone,sandstone, and calcareous concretions, but includes rafts ofolder Cretaceous mudstone, perhaps in excess of 15 m long,set in a matrix of dark grey micaceous to gritty mudstone.Moore (1989b) considered that the deposits occupied a largechannel up to 200 m deep and at least 2 km wide cut intothe underlying Teratan (Coniacian) Karekare Formation. Thebreccia was inferred to be the product of cohesive debrisflows generated on the shelf by retrogressive slumpingassociated with a growing fold and minor faulting. Breccia,consisting of large (up to 10 m) blocks of older Cretaceousrocks, also occurs locally in strata of Piripauan to EarlyHaumurian age in northern Wairarapa (Moore 1980). Nosignificant coarse clastic deposits have, however, beenrecognised in the later Haumurian (late Campanian-Maastrichtian). By contrast, conglomerates at Tora areprominent in the Late Haumurian and early Paleocene.

Slumping has been recognised in the upper (Paleocene)part of the Whangai Formation in northern Wairarapa (Moore1988b), but is rare and localised in the Late Cretaceous. InRaukumara Peninsula, slumping is associated with Kirk'sBreccia of Early Haumurian age. In Marlborough, wherethe Whangai Formation equivalents are restricted to theHaumurian, slumping in the Late Haumurian has beenrecorded only in Woodside Creek, southwest of Ward (Fig.1), where it is present at one horizon (Laird pers. obs.). OlderHaumurian locally contains slumps in the coastal area eastof Ward (Laird pers. obs.). By contrast, slumping at Torawas recognised only in the latest Haumurian portion of theWhangai Formation.

Apart from the channel containing Kirk's Breccia (seeearlier), which is restricted in age to Late Piripauan to EarlyHaumurian (Santonian to early Campanian), no majorchannel systems of Late Cretaceous-Paleocene age havepreviously been recorded from the East Coast Basin.However, most other deposits of that age record much deeperwater depths where perhaps channels would be less likelyto form.

The occurrence of hummocky cross-stratification in theupper part of the Whangai Formation at Tora suggests thatdeposition of the unit occurred in shelf depths affected byfrequent storms. This latter feature appears to be unique tothe Tora area, as it has not so far been recognised from thisunit elsewhere in the East Coast Basin. In southern Hawke'sBay and in Marlborough, however, depths were inferred tobe outer shelf or bathyal, at least locally (Wilson et al. 1989;Hollis 1996), and the seafloor is likely to have been out ofthe range of disturbance by storms.

CONCLUSIONS

The Late Cretaceous to early Paleocene succession at Toraconsists predominantly of very fine to medium sandstone,with minor limestone, mudstone, and breccia conglomerate,inferred to have been emplaced mainly in shelf depths. Itrecords probable marine transgression in the latestCretaceous (late Maastrichtian), followed by erosion andrapid regression in the earliest Paleocene.

The sequence includes features unique within the EastCoast Basin. The occurrence of hummocky cross-stratification in the Whangai Formation has not beenrecognised elsewhere in that unit, or in other latestCretaceous deposits in New Zealand, although this may bepartly a factor of depth of deposition. The cause of the stormactivity, which is inferred to have resulted in the structure,remains speculative. One possibility is that latest Cretaceousclimatic cooling in the Southern Ocean may have initiatedan episode of more vigorous atmospheric circulation anddisturbance (Hollis et al. 1995; Hollis 1996). This suggestionis supported by the enhanced upwelling, probably wind-driven, which resulted in an increase in surface productivitycausing a dramatic increase in siliceous microfossilabundance and chert in the earliest Paleocene inMarlborough (Hollis et al. 1995; Hollis 1996).

Manurewa Formation, which spans the K/T boundary,represents a nested channel complex with active erosion andinfill during the Late Haumurian (late Maastrichtian), andagain in the early Teurian (early Paleocene). The Teurianchannel overlaps the Haumurian one to the southwest; theformer may be >9 km wide, and the latter >4 km, with infillthicknesses of up to c. 18 m of sediment in each.

Both Manurewa Formation and Whangai Formationinclude olistostromes containing outsize clasts up to 3 m inlength, including blocks of older Cretaceous strata. Theseare attributed to tectonic uplift and erosion in the sourcearea, although tectonism appears to be anomalous in apassive margin tectonic setting. Tectonic activity may alsoaccount for the common occurrence of slump horizons inthe upper Whangai Formation in the Tora area, slumpingbeing a rare feature elsewhere in the Haumurian strata ofthe East Coast Basin (Moore 1988b).

There is evidence of relative sea-level changes affectingsuccessive units. The Late Cretaceous portion of theManurewa Formation channel system is inferred to be deeperthan the shelf depths of the Whangai Formation into whichit is eroded, and a relative sea-level rise in latest Cretaceoustimes during deposition of the older channel-fill member ofthe Manurewa Formation seems likely. The younger, earlyTertiary portion of the Manurewa channel system is inferredto correspond with an abrupt relative sea-level fall in theearliest Paleocene. The succession continued to shallow intothe Awhea Formation, which is interpreted as very shallowmarine, occupying an inshore environment in the southwest.

The earliest Paleocene relative sea-level fall inferred atTora has also been suggested in other K/T boundarysuccessions in the East Coast Basin (see Strong 1977; Wilsonet al. 1989; Moore 1989a; Hollis et al. 2003a). Neither thisfall nor the inferred latest Cretaceous relative sea-level riseappear on global eustatic charts (e.g., Haq et al. 1987; DeGraciansky et al. 1998), and the changes of relative sea levelare probably attributable to regional tectonic activity ratherthan to eustasy.

A feature common to Tora and to the well-studied K/Tboundary sequences in southern Hawke's Bay and eastern

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Marlborough is a discontinuity at the K/T boundaryrepresenting a hiatus or an erosion interval. However, whilethere is a noticeable increase in glauconite above the K/Tboundary in both southern Hawke's Bay and at Tora, this isnot evident in Marlborough, where instead there is a markedincrease in silica. On the other hand, the highly calcareousK/T boundary succession in Marlborough appears to bereflected in part by the intercalated layers of limestone andcalcareous sandstone and mudstone in the ManurewaFormation, particularly in the Lower Member, whilecarbonates are minor or absent in the southern Hawke's Baysuccession.

In conclusion, the latest Cretaceous to earliest Tertiarysuccession at Tora represents a link between the K/Tboundary successions in Hawke's Bay and Marlborough. Itindicates that the change in lithofacies between the sectionsfrom north to south is transitional, and helps to confirm thestructural integrity of the East Coast Basin. Some of thecontrasts in lithofacies between the Tora area and those tothe north and south almost certainly derive from the moreinshore environment of the Tora succession (Fig. 12), andthe effect of contemporaneous tectonism.

ACKNOWLEDGMENTS

MGL, KNB, JDB, and SDW acknowledge support from the NewZealand Foundation for Research, Science and Technology (FRST)(Contract No. MGLX001). PS acknowledges a research grant fromthe Carlsberg Foundation, Copenhagen, and support from FRST(GNS Contract No. C0X0002) and the Marsden Fund (ContractGNS703) HEGM also acknowledges support from FRST (ContractNo. C05X0002). M. Hannah and an anonymous referee are thankedfor their comments, which have greatly improved the manuscript.

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Wilson, G. J. 1987: Dinoflagellate biostratigraphy of theCretaceous-Tertiary boundary, mid-Waipara River section,North Canterbury, New Zealand. New Zealand GeologicalSurvey Record 20: 8-15.

Wilson, G. J. 1988a: Paleocene and Eocene dinoflagellate cystsfrom Waipawa, Hawkes Bay, New Zealand. New ZealandGeological Survey Paleontological Bulletin 57. 96 p.

Wilson, G. J. 1988b: The Cretaceous-Tertiary boundary, mid WaiparaRiver. New Zealand Geological Survey Record 33: 94-98.

Wilson, G. J.; Moore, P. R. 1988: Cretaceous-Tertiary boundaryin the Te Hoe River area, western Hawke's Bay. NewZealand Geological Survey Record 35: 34-37.

Wilson, G. J.; Morgans, H. E. G.; Moore, P. R. 1989: Cretaceous-Tertiary boundary at Tawanui, southern Hawkes Bay, NewZealand. New Zealand Geological Survey Record 40: 29–40.

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