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

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achiopod orders that had survived into the Triassic, had finally disappeared, and brachiopod faunas in New Zealand, as elsewhere, became dominated by a variety of ribbed rhynchonellides with a few species of generally smooth terebratulides making up the balance. Little is known of New Zealand Cretaceous brachiopods, but from the early Cenozoic to the present day, in New Zealand seas as globally, terebratulides have become by far the most abundant and diverse group of brachiopods, greatly outnumbering rhynchonellides in terms of both generic and species richness, and in total biomass. What caused this major shift or changeover in brachiopod faunas since the Mesozoic? Was competition between brachiopods and bivalves a factor? Did the endopunctate terebratulides come through the Mesozoic Marine Revolution more successfully than impunctate rhynchonellides because of superior morphological, physiological and ecological characteristics? We will examine the morphological differences between the two groups, and indicate how these may have enabled the two brachiopod clades to cope with various environmental changes (ocean chemistry, temperature and sea level fluctuations, varied substrates) and biotic filters (competition, feeding efficiency, predation) over the past 200 million years. Our analysis uses examples from New Zealand Mesozoic and Cenozoic strata, and the modern New Zealand brachiopod fauna. ORAL SOUTH ISLAND OLIGOCENE UNCONFORMITIES – EVOLUTION OF AN IDEA Helen Lever Department of Geological Sciences, University of Canterbury, Christchurch. (helen.lever*canterbury.ac.nz) Early mapping in the Canterbury and Otago regions quickly generated controversy about the interpretation of the contact between the Amuri and Weka Pass Limestones and their stratigraphic equivalent. Mappers were divided on whether the contact was conformable or unconformable. In publications (up to the 1960s) the contact is well described, but is never referred to as an unconformity. In the Oamaru region the two limestones are often separated by a unit of calcareous glauconitic sandstone, and the faunal differences between the underlying limestone (correlated with the Amuri in Canterbury), the glauconitic sandstone and the overlying limestone (correlated with the Weka Pass Limestone) led to the subdivision of the Oligocene into the New Zealand stages Whaingaroan, Duntroonian and Waitakian. It was not until the biostratigraphy of the Oligocene was much better defined that a definite age break between the Amuri and Weka Pass Limestones was proved, and by this time the correlation of these limestone units was so well established that it was an easy logical step to assume that the age of the unconformity must therefore be the same wherever the two limestones occur. At this time the Tertiary succession in the South Island was being interpreted as a transgressiveregressive sequence, with the boundary between the two limestones representing starvation due to maximum sea-level. Alternatively, global studies were connecting the change from Greenhouse to Icehouse climates with the development of a strong current circling Antarctica, at around the beginning of the Oligocene. Both these theories were advanced to explain synchronous development of unconformities across the South Island and into the offshore regions. However, the unconformity itself is quite different across the South Island, and may not be present in some successions. Biostratigraphic studies have confirmed the presence of multiple unconformities within many successions, although only one at others. Other dating methods are more difficult to apply, and only strontium isotope dating has been attempted at what has been described as the type section of the regional unconformity, at Squires Farm in South Canterbury. This date proved to be slightly inconsistent with earlier interpretations and some biostratigraphic results for other successions, but correlates well with some offshore dating from ODP Leg 181. The current status is impasse, with interpretation of the unconformities as being caused by a single event still the dominant explanation, but insufficient data available to either prove or disprove this hypothesis. POSTER DEPOSITIONAL PROCESSES AND SEDIMENTARY FRACTIONATION IN THE FORMATION OF TEPHRA BEDS FROM PYROCLASTIC ERUPTIONS: A STUDY OF POTAKA AND CORRELATIVE KAIMATIRA PUMICE SAND DEPOSITS 1 Lewis B., 1 White J.D.L., 2 Manville V., & 1 Palin J.M. 1 Dept. of Geology, University of Otago, P.O Box 56, Dunedin 2 Institute of Geological & Nuclear Sciences, Wairakei Research Centre, Private Bag 2000, Taupo (grumpsnz*yahoo.co.nz) 50 th Kaikoura05 -44- Kaikoura 2005
Tephra beds are commonly used to aid in chronostratigraphic reconstruction of sedimentary deposits within which they occur. High-resolution stratigraphic studies of Wanganui Basin sediments have benefited from the abundance of interlayered tephras, many of which have been dated by fissiontrack methods and/or are correlated with known eruptions in the Taupo Volcanic Zone. The present study has a different aim; which is to investigate the physical processes involved in sedimentary deposition of ash in the marine environment. To do so we are examining the Potaka Tephra at two sites, and the correlative Kaimatira Pumice Sand at another two sites. The Potaka Tephra locally contains apparently unreworked primary tephra deposits, but through most of its thickness reflects deposition under the influence of waves and currents. Kaimatira Pumice Sand consists of crystals and uncommon pumice fragments derived from pyroclastic deposits, but deposition was entirely by waves and currents, and the original pyroclastic grain population has been reduced to a "lag" of crystals representing an as-yet undetermined fraction of the mixture of crystalbearing pumice, glass shards, and free crystals that would have characterised the primary particle population. Our analysis will focus on (1) using bedding structures to determine as precisely as possible the depositional processes that formed different parts of the tephras, (2), geochemical investigation of glass, crystals, and whole pumice to characterise the tephras, for comparison with known primary eruptive products of the TVZ, and (3), for primary parts of the Potaka tephra, determine fine-scale details of the bedding structure and variations in particle population, and interpret these in terms of the processes active in deposition of particles that have been deposited via sedimentation through both air (from the eruptive plume), and water. POSTER HIGH-RESOLUTION PALEOCLIMATE SIGNAL FROM EARLY MIOCENE LACUSTRINE DIATOMITE NEAR MIDDLEMARCH, CENTRAL OTAGO, NEW ZEALAND J.K. Lindqvist &D.E.Lee Department of Geology, University of Otago, P.O. Box 56 Dunedin, New Zealand (jonlind*es.co.nz) A 75-100+ m thick lacustrine diatomite succession near Middlemarch, 45 km northwest of Dunedin, accumulated in a ~1 km diameter maar depression in schist basement. Two diatomite facies are recognised. A thinly laminated biogenic varve facies comprises c.60 % of the 11m lacustrine succession exposed in two mining test pits. This facies consists of diatom-rich light and dark couplets of average thickness
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 and 38: faunal changes within these cores w
Page 39 and 40: material at subsurface depths of se
Page 41 and 42: survived through in low numbers in
Page 43: in the TVZ and southern Havre Troug
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
Page 91 and 92: 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
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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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