Paleoenvironmental and tectonic changes across the Cretaceous/Tertiary boundary at Tora, southeast Wairarapa, New Zealand: A link between Marlborough and Hawke's Bay

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<ul><li><p>This article was downloaded by: [Universitat Politcnica de Valncia]On: 04 November 2014, At: 03:35Publisher: Taylor &amp; FrancisInforma Ltd Registered in England and Wales Registered Number: 1072954 Registered office: MortimerHouse, 37-41 Mortimer Street, London W1T 3JH, UK</p><p>New Zealand Journal of Geology and GeophysicsPublication details, including instructions for authors and subscription information:http://www.tandfonline.com/loi/tnzg20</p><p>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. Schiler b , H. E. G. Morgans c , J. D. Bradshaw a &amp; 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 &amp; Nuclear Sciences , P.O. Box 30 368, Lower Hutt, New ZealandPublished online: 21 Sep 2010.</p><p>To cite this article: M. G. Laird , K. N. Bassett , P. Schiler , H. E. G. Morgans , J. D. Bradshaw &amp; 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</p><p>To link to this article: http://dx.doi.org/10.1080/00288306.2003.9515009</p><p>PLEASE SCROLL DOWN FOR ARTICLE</p><p>Taylor &amp; Francis makes every effort to ensure the accuracy of all the information (the Content) containedin the publications on our platform. However, Taylor &amp; Francis, our agents, and our licensors make norepresentations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose ofthe Content. Any opinions and views expressed in this publication are the opinions and views of the authors,and are not the views of or endorsed by Taylor &amp; Francis. The accuracy of the Content should not be reliedupon and should be independently verified with primary sources of information. Taylor and Francis shallnot be liable for any losses, actions, claims, proceedings, demands, costs, expenses, damages, and otherliabilities whatsoever or howsoever caused arising directly or indirectly in connection with, in relation to orarising out of the use of the Content.</p><p>This article may be used for research, teaching, and private study purposes. Any substantial or systematicreproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in anyform to anyone is expressly forbidden. Terms &amp; Conditions of access and use can be found at http://www.tandfonline.com/page/terms-and-conditions</p><p>http://www.tandfonline.com/loi/tnzg20http://www.tandfonline.com/action/showCitFormats?doi=10.1080/00288306.2003.9515009http://dx.doi.org/10.1080/00288306.2003.9515009http://www.tandfonline.com/page/terms-and-conditionshttp://www.tandfonline.com/page/terms-and-conditions</p></li><li><p>New Zealand Journal of Geology &amp; 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</p><p>275</p><p>Paleoenvironmental and tectonic changes across the Cretaceous/Tertiaryboundary at Tora, southeast Wairarapa, New Zealand: a link betweenMarlborough and Hawke's Bay</p><p>M. G. LAIRD1</p><p>K. N. BASSETT1</p><p>P. SCHILER2</p><p>H. E. G. MORGANS3</p><p>J. D. BRADSHAW1</p><p>S. D. WEAVER1</p><p>1Department of Geological SciencesUniversity of CanterburyPrivate Bag 4800Christchurch, New Zealand</p><p>2Geological Survey of Denmark and GreenlandThoravej 82400 Copenhagen, Denmark</p><p>3Institute of Geological &amp; Nuclear SciencesP.O.Box 30 368Lower Hutt, New Zealand</p><p>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.</p><p>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 &gt;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</p><p>G02013; published 30 June 2003Received 28 February 2002; accepted 10 March 2003</p><p>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.</p><p>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.</p><p>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.</p><p>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</p><p>INTRODUCTION</p><p>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/</p><p>Dow</p><p>nloa</p><p>ded </p><p>by [</p><p>Uni</p><p>vers</p><p>itat P</p><p>olit</p><p>cnic</p><p>a de</p><p> Val</p><p>nci</p><p>a] a</p><p>t 03:</p><p>35 0</p><p>4 N</p><p>ovem</p><p>ber </p><p>2014</p></li><li><p>276 New Zealand Journal of Geology and Geophysics, 2003, Vol. 46</p><p>and Dido1 urala</p><p>&amp;eclh7i tocotrv</p><p>Unatna</p><p>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.</p><p>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).</p><p>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</p><p>may also have affected the degree and location of thisactivity.</p><p>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).</p><p>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 &amp; Bradley 1957). Its</p><p>Dow</p><p>nloa</p><p>ded </p><p>by [</p><p>Uni</p><p>vers</p><p>itat P</p><p>olit</p><p>cnic</p><p>a de</p><p> Val</p><p>nci</p><p>a] a</p><p>t 03:</p><p>35 0</p><p>4 N</p><p>ovem</p><p>ber </p><p>2014</p></li><li><p>Laird et al.Paleoenvironment at K/T boundary, SE Wairarapa 277</p><p>Scalem</p><p>- 40</p><p>swTe Kaukau Point</p><p>i T T lTime Scale S</p><p>Pukemuri</p><p>Stream</p><p>NE</p><p>ManurewaPoint</p><p>..-</p><p>. 9.5</p><p>A. homomorphum</p><p>g K / TBoundary</p><p>LEGEND</p><p>X^^\ siltstone</p><p>[ . ; . . ] sandstone</p><p>H&amp;J clast-s up ported|gy&amp; conglomerate[ ens e matrix-supported' en se conglomerate[^.^| with outsize clastsll a ry limestone/</p><p>I-on e/ calcareous beds</p><p>thin - bedded</p><p>- bedded</p><p>hummockybedding</p><p>concretionsc bioturbation</p><p>g glauconite</p><p>F. </p><p>I. cretaceum -* . ' . . l . : - : - ' . : . / -</p><p>- F.</p><p>GLENBURNFORMATION</p><p>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.</p><p>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.</p><p>LATEST CRETACEOUS AND EARLY PALEOCENESTRATIGRAPHY OF THE TORA AREA</p><p>Previous work and geographic settingPrevious studies of the Late Cretaceous and earliest Tertiaryrocks of the Tora area of southeast Wairarapa are sparse.Waterhouse &amp; 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</p><p>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.</p><p>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.</p><p>Glenburn FormationDescription</p><p>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</p><p>Dow</p><p>nloa</p><p>ded </p><p>by [</p><p>Uni</p><p>vers</p><p>itat P</p><p>olit</p><p>cnic</p><p>a de</p><p> Val</p><p>nci</p><p>a] a</p><p>t 03:</p><p>35 0</p><p>4 N</p><p>ovem</p><p>ber </p><p>2014</p></li><li><p>278 New Zealand Journal of Geology and Geophysics, 2003, Vol. 46</p><p>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.</p><p>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 horizon...</p></li></ul>

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