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

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investigations in the 60’s and 70’s. The active central vents shows a combination of prheatomagmatic to magmatic explosive and effusive events that are seemingly strongly controlled by the hydrogeology and architecture of the island. Marum and Benbow are well-developed tuff cones with deep and complex craters, where pit crater formation as well as phreatomagmatic explosive eruption induced crater subsidence play a major role in their formation. Flank eruptions forming monogenetic fields commonly started with central eruptions such as in 1913, suggesting a strong coupling mechanism of central and flank eruptions. Magma rise in the centre of the island, followed by intense degassing and drainage of degassed magma along lateral dykes is inferred by us to be the major means by which the central 12km wide caldera slowly formed. This caldera formed over a long-term stable shallow magma storage system. Hence we suggest, that the theory of the “giant tuff cone” is not necessary to explain the volcaniclastic facies associations of Ambrym, and the formation of its caldera. This volcano should hence never be used as a comparative example for large-scale explosive phreatomagmatism – as has been done on several occasions since the mid 90’s. This conclusion also highlights that the volcanic hazard of Ambrym is rather dominated by the potential interaction of magma and water along the NW and SE rift edge and the style of eruptions in the central vent rather than potential major caldera forming events that may disrupt the island and impact upon the region. ORAL EARLY PALEOGENE BIOSTRATIGRAPHIC RECORD FROM THE NERITIC MID- WAIPARA RIVER SECTION, NORTH CANTERBURY E. M. Crouch, H.E.G. Morgans, B.D. Field, C.M.Jones,J.I.Raine,C.P.Strong& G.J. Wilson GNS Science, PO Box 30368, Lower Hutt (e.crouch*gns.cri.nz) Detailed studies of early Paleogene South Pacific sedimentary records are limited, but are critical in providing proxy data for validating general circulation models and understanding natural processes that led to major perturbations in carbon cycling and global climate. Some of the most complete South Pacific early Paleogene records are from distal pelagic successions in the Clarence Valley, Marlborough, but corresponding wellexposed records from proximal settings are currently limited. The mid-Waipara River Section, North Canterbury, has a well-exposed and near continuous early Paleogene shelf succession, providing an opportunity to document biological and sedimentological response to climatic changes in a proximal setting during the Paleocene to Middle Eocene (~65–46 Ma). From the mid-Waipara River Section, a detailed suite of 265 samples has been collected from Paleocene, Paleocene/Eocene boundary, and Early to Middle Eocene successions of the Conway and Loburn Formations, Waipara Greensand and Ashley Mudstone. All samples are incorporated in a detailed tape and compass survey map, and the collections are documented in six lithologic columns that represent a geographic and stratigraphic progression from the westernmost (oldest) to the easternmost (youngest) location (Morgans et al., 2005). Integrated studies of sedimentology, foraminifera, dinoflagellate cysts, calcareous nannofossils, spores/pollen, and carbon isotopes are being completed. Biostratigraphic results suggest the top of the Conway Formation youngs in an eastward direction from uppermost Cretaceous in the Waipara South Branch section to lower Paleocene in the mid- Waipara River section. A near-complete ~120 m thick Paleocene record is sampled, with diverse calcareous and organic-walled microfossil assemblages in the Early and early Late Paleocene. Calcareous faunas are absent throughout most of the Waipara Greensand (Late Paleocene) and age control is primarily from dinoflagellate cysts. Initial bulk organic � 13 C isotope results suggest the late Paleocene carbon isotope maximum (~59.5–56 Ma) is present in the upper Waipara Greensand (Stormont Member), along with a geochemical signature that is characteristic of the Waipawa (Black Shale) Formation. The Paleocene/Eocene boundary, or initial Eocene thermal maximum (~55 Ma), is tentatively recognised in the uppermost Waipara Greensand, however further palynological and � 13 C isotope analyses are needed. While continuous in-situ earliest Eocene (Waipawan) sediments are not presently exposed, a detailed Early to Middle Eocene (Mangaorapan– Heretaungan) Ashley Mudstone record indicates most of the Early Eocene climatic optimum (~53– 50 Ma) is represented. Morgans, H.E.G., Jones, C.M., Crouch, E.M., et al., 2005: Upper Cretaceous to Eocene stratigraphy and sample collections, mid-Waipara River Section, North Canterbury. Institute of Geological and Nuclear Sciences science report 2003/08. 101 p. ORAL 50 th Kaikoura05 -22- Kaikoura 2005
VEGETATION AND CLIMATE CHANGE AT THE PALEOCENE-EOCENE TRANSITION E.M. Crouch, J.I. Raine & E.M. Kennedy GNS Science, PO Box 30368 Lower Hutt. (e.crouch*gns.cri.nz) Plant microfossil (spore/pollen) assemblages from New Zealand Paleocene–Eocene (P–E) sedimentary sections show a general change from predominantly gymnosperm-rich Paleocene floras (zone PM3) to Casuarina-dominated angiosperm-rich floras in the Early Eocene (zone MH1). Modern relatives of the fossil plant taxa and vegetation analogues indicate this change is related to significant climatic warming, although the precise timing and extent of more subtle vegetation change during the P–E transition remains poorly documented. Previous studies (e.g., Tawanui section, Hawkes Bay, and Moeraki-Hampden section, Otago) suggest that the main vegetation change in the Paleocene–Eocene occurred in the upper Waipawan Stage (earliest Eocene) and post-dated the significant climatic and carbon cycle perturbation at the P–E boundary (~55 Ma). Plant microfossil records are currently being studied from a silica-sand quarry at Mt Somers, South Canterbury, and in the Kumara-2 core, central Westland, to elucidate the timing and scale of vegetation change during the P–E transition. Gymnosperm pollen and Proteaceae and small triporate angiosperm pollen are abundant in the lower part of the Kumara-2 core (1739-50 m), and a Late Paleocene age is suggested. Coastal marine sediments are present from ~1733-38 m, with abundant cysts of the marine dinoflagellate genus Apectodinium recorded in the middle of this unit. Coincident with the base of the marine horizon, pollen indicative of warm climates (e.g., Cupanieidites orthoteichus, Spinizonocolpites prominatus) are first recognised and become a recognisable component of the spore/pollen assemblage. Spores/pollen are absent from a channel fill sand at 1722-33 m, but above this unit the assemblage is diverse, angiosperm pollen are abundant and Casuarina pollen (zone MH1) markedly increase in the upper part of the studied core. Abundant Apectodinium dinocysts in the coastal marine unit suggests this interval lies very close to the P–E boundary, and it appears this marine incursion may be related to a thermal expansion of ocean waters and slight sea-level rise at the time of extreme warming at the P–E boundary. Compound-specific organic carbon isotope analyses are currently being completed to confirm the presence and position of the P–E boundary. Within the sand dominated Broken River Formation-Homebush Sandstone section at Mt Somers, fine-grained mudstone layers were sampled where possible and palynomorph assemblages examined. A Late Paleocene sample contains common gymnosperms and appears to be terrestrial, although marine dinocysts have previously been recorded from a similar horizon. Above this, a prominent ~3 m grey mudstone contains abundant cysts of the marine dinoflagellate genus Apectodinium, indicating an early Waipawan age. Marine conditions persist in the overlying mudstone layers examined, with an uppermost glauconitic sandstone unit containing dinocysts indicative of the Mangaorapan Stage. Pollen indicative of warm climates are present by the early Waipawan (prominent mudstone unit), and Casuarina pollen (zone MH1) is abundant in the upper glauconitic sandstone unit. POSTER “100 KM PER MILLION YEARS” A HIGHLY-DYNAMIC DEPOSITIONAL MODEL FOR LATE MIOCENE ROCKS IN TARANAKI BASIN Martin Crundwell &MalcolmArnot Geological and Nuclear Science Limited, PO Box 30-368, Lower Hutt, NZ (m.crundwell*gns.cri.nz) New biostratigraphic dating techniques challenge traditional exploration paradigms and suggest a highly dynamic depositional model is more appropriate for late Miocene rocks in Taranaki Basin, with multiple deep-water sedimentary systems of considerable thickness, developed on local geographic scales, over timescales of orbital proportions (40-100 kyr). Although the general pattern and tempo of late Miocene sedimentation are clearly dictated by climate forcing, suborbitalscale variations in sedimentary patterns and rates of deposition reflect a complex history of shelf progradation, tempered by sediment supply and accommodation, and tectonic controls within and adjacent to the basin. The observed dynamism in sedimentation is consistent with the tectonic development of the eastern Taranaki Basin margin (e.g. King and Thrasher, 1996), and with detailed outcrop based stratigraphic studies undertaken by GNS (e.g. King et al., 1993; Browne and Slatt, 2002), and also with many of the problems associated with hydrocarbon reservoir sequences (e.g. poor correlation and dating, rapid facies variations, and variable reservoir characteristics). In this presentation, we outline some of the new biostratigraphic tools that have been developed specifically to address correlation problems associated with late Miocene rocks in Taranaki Basin. Examples from Pukearuhe-1 and outcrop studies are given, of extremely high estimated rates of sedimentation, based on weight standardized counts of planktic and benthic foraminifers, 50 th Kaikoura05 -23- Kaikoura 2005
Page 1 and 2: CHARACTERISATION OF NEW ZEALAND NEP
Page 3 and 4: myrtaceous. One 20 mm diameter flow
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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
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Page 17 and 18: the LGM grass peak. This period of
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Page 29 and 30: TRACKING CRUSTAL DIFFERENTIATION AN
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Page 65 and 66: THE GRIFFENS ROAD TEPHRAS: VALUABLE
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landslide tsunami in the past. Rece
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core complex mode, temperature driv
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truncating three plutonic suites of
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active, andesitic White Island volc
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and voluminous than at any on Earth
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oundaries and with immature source
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The new era of commercial viability
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TECTONICS OF THE GALATEA BASIN USIN
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performed by the electron backscatt
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25km northeast of the volcano. Alth
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Most of the tectonic blocks in the
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TECTONIC AND NON-TECTONIC CAUSES OF
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The continental shelf of the Povert
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5 Dept. of Mineral Sciences, Smiths
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Adams CJ...........................
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Naish T............................
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