50thKaikoura05 -1- Kaikoura 2005 CHARACTERISATION OF NEW ...

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QUATERNARY TEPHRA BEDS PRESERVED ON CHATHAM ISLAND: THEIR IDENTIFICATION AND SIGNIFICANCE IN INTERPRETING ASSOCIATED DEPOSITS AND PALEOVEGETATION Kat Holt Institute of Natural Resources, Massey University, Palmerston North, N.Z. (k.holt*massey.ac.nz) The Chatham Islands preserve the easternmost occurrences of terrestrial Quaternary deposits of the New Zealand microcontinent. These include dune sands, loess, extensive blanket peats, and rhyolitic tephras derived from the TVZ in mainland New Zealand. At least three separate rhyolitic events are preserved as macroscopic tephra beds at many different locations around Chatham Island. The youngest of these is the well known and well dated Kawakawa Tephra, which is ubiquitous about the Island, occurring in peat, sand, colluvium and loess deposits, providing an excellent marker for LGM studies on the Island. The c.340 ka Rangitawa Tephra is present at three or more sites around the Island. At one of these locations it occurs less than two metres below the Kawakawa Tephra, indicating either extended periods of non-deposition or periods of erosion at these sites on the Island during the mid to late Quaternary. In addition, devitrified tephra beds at three different localities have been recognised using ferromagnesian mineral content and geochemistry of ilmenite grains. At present, their ages are still unknown, but zircon grains preserved within these tephras are to be fission track dated which will aid in identifying them. The occurrences and stratigraphic significance of the various tephras will be discussed in relation to the landscape evolution and vegetation history of Chatham Island. ORAL PETROLOGY OF TRANSGRESSIVE COOL- WATER LIMESTONE SEQUENCES IN NORTHERN TE KUITI GROUP, WAIKATO BASIN, NEW ZEALAND S.D. Hood, A. Tripathi, C.S. Nelson & P.J.J. Kamp Department of Earth Sciences, University of Waikato, Private Bag 3105, Hamilton (s.hood*waikato.ac.nz) The mainly Oligocene Te Kuiti Group is a broadly transgressive mixed-siliciclastic cool-water carbonate succession occurring in King Country and Waikato Basins, central western North Island. The group consists of six 3rd to 4th order (1 to 5 Ma) sequences. Each of sequences 2 to 6 includes a major transgressive limestone unit at their base. The field characteristics and petrology of these limestones are little known in the Waikato Basin (from Port Waikato to Kawhia) in contrast to their correlatives to the south in King Country Basin (includes Te Kuiti/Waitomo area). Current study of these northern limestone units is providing new insights into the evolution of the Waikato Basin during the Oligocene. The earliest Oligocene Elgood limestone of sequence 2, the lowermost of the Te Kuiti Group limestones, commonly onlaps onto Mesozoic basement rocks (e.g. Port Waikato). This limestone is tight, flaggy, well-cemented, c.10-12 m thick, and comprises pure biosparites, and occasionally biomicsparites. Skeletons are dominated by calcareous red algae, bryozoans, benthic foraminifera, and echinoderms, suggestive of shallow-shelf water depths. The mid-Oligocene Awaroa Limestone of sequence 3, onlapping onto Ahirau Sandstone, is restricted to the Kawhia region, has a flaggy appearance, and is commonly 10-18 m thick. Rocks are dominated by bryozoan, benthic foraminiferal, and echinoderm biosparites suggestive of mid-shelf water depths. The mid-Late Oligocene Waimai Limestone of sequence 4 onlaps Kotuku Siltstone and is distinctly tabular crossbedded. Rocks include a spectrum of biosparites through to rarer biomicrites. Bioclasts are dominantly bryozoans, echinoderms, and benthic foraminifera typical of mid-shelf water depths. The late Oligocene Raglan Limestone of sequence 5 is commonly c.10 m thick, locally up to 20 m, and is restricted to northern Raglan Harbour area. This limestone transgressed onto Patikirau Siltstone, and is a slabby, intensely bioturbated, planktic foraminiferal biomicrite indicative of accumulation at outer-shelf water depths. The latest Oligoceneearliest Miocene Otorohanga Limestone or its equivalent of sequence 6, the uppermost limestone of the Te Kuiti Group, onlaps the Waitomo Sandstone and is restricted in occurrence to Gibson’s Beach. The limestone is a flaggy, dense, well-cemented, pure limestone c.8 m thick. Rocks are bryozoan, echinoderm, benthic foraminiferal dominated biomicsparites indicative of mid to outer-shelf water depths. Data suggest that during the Oligocene Waikato Basin experienced six major transgressive events characterised by siliciclastic sediment starvation and the establishment of carbonate factories at commonly inner- to mid-shelfal depths. Sea level changes were probably mainly tectonically driven with a superimposed glacio-eustatic component. The calcite cementation of these limestones is consistent with burial-induced cementation associated with pressure-dissolution of skeletal 50 th Kaikoura05 -38- Kaikoura 2005
material at subsurface depths of several 100s of metres. POSTER MECHANICAL PARAMETERS AND SEDIMENT RHEOLOGY IN THE SUBMARINE MATAKAOA AVALANCHES, EAST CAPE REGION C. Joanne 1 ,T.Lebourg 1 ,G.Lamarche 2 , J.-Y. Collot 1 ,S.Migeon 1 1 UMR Géosciences Azur, 06235 Villefranche-sur- Mer, France 2 NIWA, Private Bag 14-901, Wellington. (joanne*geoazur.obs-vlfr.fr) Swath bathymetry and seismic reflection data acquired over the 45 km-long, ~30 km-wide Matakaoa re-entrant provide evidence of active erosion and mass failure processes. Slope gullies, large failure scars and channels incise the >1000 m thick, seaward dipping sedimentary section of the northern margin of the East Cape region. Seismic reflection profiles from the East of the re-entrant show single catastrophic debris avalanche of low recurrence, whereas profiles acquired along the reentrant axis provide evidences of repetitive debris flows resulting from regular failures of the recent sediments cover. Deep-seated anticlines and the proximity of the active subduction front of the Hikurangi Margin suggest structural and tectonic controls on this complex system of debris avalanches and debris flows that extend northward over more than 200 km. Undisturbed piston cores, collected at three sites between 600 and 1500 m water depth, provided samples for geotechnical testing. The coring sites are located on both east and west sides of the reentrant. The east of the re-entrant corresponds to a stable, undisturbed platform, whereas the west side sediment-cover presents evidence of instability. These sites were chosen to highlight possible variability in mechanical behaviour according to morpho-structural features. Sediment mechanical parameters are calculated in order to model slope instabilities and to test trigger mechanisms. Triaxial tests are conducted under high values of isotropic consolidation stresses, varying from 300 to 2000 kPa, so as to simulate stresses existing at depths of 30 to 200 m where the avalanche rupture surface is imaged on seismic profiles. The tests allow us to determine the shearing resistance, axial strain and stress deviator, and to calculate mechanical parameters as the cohesion and the effective internal friction angle. The shearing resistance is required to constrain the boundary conditions of the sediments rheology for stability models (i.e. limiting axial stress and strain at the rupture). It is also possible to determine the theoretical boundary between stability and rupture domains. The first results of the tests give internal friction angles ranging from 22º to 25°, and undrained cohesion values from 0 to 30 kPa. Using these mechanical parameters in the stability equation (finite elements modelling and Mohr- Coulomb rupture criteria) will help to understand the role of external parameters (e.g., variations in sea-level, seismic accelerations, lithostatic loading) in the triggering of failures in the Matakaoa landslides. The modelling of slope instabilities will help to constrain the modalities of emplacement of the multiple phases observed in the Matakaoa submarine avalanche complex. ORAL THE FIRST PTEROSAUR BONE FROM THE LATE CRETACEOUS OF THE SOUTH ISLAND, NEW ZEALAND Craig M. Jones, Institute of Geological and Nuclear Sciences, (c.jones*gns.cri.nz) New Zealand’s record of Mesozoic terrestrial vertebrates is very limited; almost all of the specimens have come from the Late Cretaceous shallow marine sediments exposed in Mangahouanga Stream, Southern Hawkes Bay. Most were collected and described by Dr. Joan Wiffen and others. Included in the known fauna are Pterosaurs which are represented by a scapula? and the distal end of an ulna. Recently the author discovered an uncatalogued bone in the reference collection of the Institute of Geological and Nuclear Sciences (GNS, formerly the New Zealand Geological Survey). The specimen is a large, hollow, very thin-walled distal? portion of a long bone. It is poorly preserved with few identifiable anatomical features. The surfaces on the end of the bone are damaged or worn. It is tentatively identified here as the distal? end of an, as yet, unidentified pterosaur wing long bone. The referral of the specimen to the Order Pterosauria is based on its large size (20 mm minimum shaft diameter), hollow shaft (now infilled with sediment), and very thin walls (1 mm thick). The shaft has a flattened, ovoid crosssection. The specimen was collected by C.A. Fleming in May 1955 from the “Black Grit”, Mikonui Stream, near Haumuri (Amuri) Bluff, just south of Kaikoura. This unit (equivalent to the Tarapuhi Grit of Warren and Speden 1977) has recently been redated, using improved dinoflagellates biozonations, as lower Middle Campanian (Crampton et al 2000). 50 th Kaikoura05 -39- Kaikoura 2005
Page 1 and 2: CHARACTERISATION OF NEW ZEALAND NEP
Page 3 and 4: myrtaceous. One 20 mm diameter flow
Page 5 and 6: ange of lower resolution or fragmen
Page 7 and 8: CRETACEOUS-EOCENE TRANSGRESSION MAR
Page 9 and 10: consists of a well-developed canyon
Page 11 and 12: model. The relative position of the
Page 13 and 14: converts to plate theory. Thus, the
Page 15 and 16: and on the following morning the mi
Page 17 and 18: the LGM grass peak. This period of
Page 19 and 20: offshore west coast to offshore eas
Page 21 and 22: 4 Institut de Recherche pour le Dé
Page 23 and 24: VEGETATION AND CLIMATE CHANGE AT TH
Page 25 and 26: wider range. The youngest layer has
Page 27 and 28: few normal faults visible especiall
Page 29 and 30: TRACKING CRUSTAL DIFFERENTIATION AN
Page 31 and 32: EMPIRICAL SCALING RELATIONS FOR SEI
Page 33 and 34: hydrovolcanic eruptions then took p
Page 35 and 36: and that the MTL marks a Late Carbo
Page 37: faunal changes within these cores w
Page 41 and 42: survived through in low numbers in
Page 43 and 44: in the TVZ and southern Havre Troug
Page 45 and 46: Tephra beds are commonly used to ai
Page 47 and 48: The MCC is bounded by deep-seated t
Page 49 and 50: distal alluvial plains where large
Page 51 and 52: Many of the molluscs in the highly
Page 53 and 54: incremental slip history and paleoe
Page 55 and 56: This paper explores what we know of
Page 57 and 58: volcanism and a linear vent oriente
Page 59 and 60: These areas are also described in
Page 61 and 62: 3D IMAGING OF THE FORE- AND BACKTHR
Page 63 and 64: ascending methane fluids/gases of p
Page 65 and 66: THE GRIFFENS ROAD TEPHRAS: VALUABLE
Page 67 and 68: sideritic concretions that occur in
Page 69 and 70: with 63.8%, and then [3] with 49.9%
Page 71 and 72: U-Th-Ra disequilibria data. In part
Page 73 and 74: landslide tsunami in the past. Rece
Page 75 and 76: core complex mode, temperature driv
Page 77 and 78: truncating three plutonic suites of
Page 79 and 80: active, andesitic White Island volc
Page 81 and 82: and voluminous than at any on Earth
Page 83 and 84: oundaries and with immature source
Page 85 and 86: The new era of commercial viability
Page 87 and 88: TECTONICS OF THE GALATEA BASIN USIN
Page 89 and 90:
performed by the electron backscatt
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25km northeast of the volcano. Alth
Page 93 and 94:
Most of the tectonic blocks in the
Page 95 and 96:
TECTONIC AND NON-TECTONIC CAUSES OF
Page 97 and 98:
The continental shelf of the Povert
Page 99 and 100:
5 Dept. of Mineral Sciences, Smiths
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Adams CJ...........................
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Naish T............................
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