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

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Inferred regional sea-level curve for the East Coast Basin. Section abbreviations are: BMS=Ben More Stream tributary; KR= Kekerengu River, headwaters; NS=Nidd Stream; UBM=Ben More Stream, upper reaches. H=Herring Formation, P=Paton Formation, HST=highstand systems tract, LST= lowstand systems tract, TST=transgressive systems tract, mf=maximum flooding, sb=sequence boundary. ORAL PETROLOGY AND TECTONICS OF EASTERN FIORDLAND: SOME EARLY RESULTS J. Scott 1 ,A.Cooper 1 ,M.Palin 1 & A. Tulloch 2 1 Geology Department, University of Otago, P.O. Box 56, Dunedin 2 Geological and Nuclear Sciences, Private Bag 1930, Dunedin (james.scott*paradise.net.nz) The paleo-Pacific arc margin to Gondwana records a dynamic (500-100 Ma) history of regional plutonism, metamorphism and tectonic activity. The behaviour and timing of these events, however, remains poorly understood. From Eastern Fiordland, New Zealand, we present some early findings of an investigation into the Paleozoic and Mesozoic evolution of this arc, and in particular structures exposed in the Manapouri region that might clarify a complex period of Early Cretaceous tectonism. The Grebe Shear Zone (GSZ) is a several hundred metres wide, steeply dipping, ductile, shear zone extending from south of Lake Hauroko at least 70km to Lake Manapouri, Fiordland. Mapping, geochemistry and petrography indicate that it forms a significant Cretaceous tectonic suture. Volcanogenic metasediments of the Jurassic Loch Burn Formation, and Paleozoic to Mesozoic diorite, gabbronorite and hypersolvus granite, crop out to the east of the GSZ. Early Paleozoic(?) psammitic and calc-silicate metasediments intruded by weakly deformed monzonites occur directly to the west. During deformation, strain was largely partitioned into ~Late Jurassic- Early Cretaceous granitic bodies. Rotated K-feldspar porphyroclasts suggest sinistral oblique slip (lineations plunge ~45° southwards). Massive granites, of similar appearance and composition to the Early Cretaceous Separation Point Suite, cut the GSZ mylonitic fabric. Dating of these post-GSZ granitoids is in progress. Moderately dipping (~30°) Tertiary unconformities on the eastern and southern limits of Fiordland suggest that the margins of the Fiordland block have been rotated from the horizontal since the Cretaceous. The extent of rotation in Central Fiordland is unknown, but is of fundamental importance to this study because two scenarios are implied. These are (1) with no block rotation the GSZ may have been an Early Cretaceous, ~vertical, oblique slip fault, active along the margin of Central Fiordland, or (2) back-rotating unconformities closest to the GSZ requires that in pre-Tertiary time the GSZ dipped (present-day) to the east, and therefore may have faulted Eastern Fiordland over Central Fiordland during the Early Cretaceous. ORAL MARINE TEPHROSTRATIGRAPHY, NORTHERN NEW ZEALAND: IMPLICATIONS FOR TAUPO VOLCANIC ZONE, MAYOR ISLAND AND WHITE ISLAND VOLCANOES Phil Shane 1 ,E.L.Sikes 2 & T. P. Guilderson 3 1 Department of Geology, University of Auckland, Private Bag 92019, Auckland 2 Institute of Marine & Coastal Sciences, Rutgers University, NJ 08901-8521 3 Lawrence Livermore National Laboratory, Livermore, CA 94551 (pa.shane*auckland.ac.nz) Twenty piston cores were collected from depths of 600-3000 m from offshore of northern North Island, New Zealand. They contain tephra from 11 Okataina Volcanic Centre and 4 Taupo Volcanic Centre rhyolite eruptions during the last ~50 kyr that produce a tephrostratigraphic framework across a tectonically and volcanically complex region of southern Havre Trough, Alderman Trough and the Bay of Plenty continental shelf. This allows onshore to off-shore correlations up to 200 km from source volcanoes, covering much of marine isotope stages 3 and 2. The framework temporally constrains poorly dated and newly recognised volcanic events. Macroscopic tephra layers from the peralkaline Mayor Island volcano are documented for the first time at pre-50 ka, post-50 ka, 39.6 ka, 36.3 ka, 21 ka, and 14.2 ka, in addition to the known 7 ka event. These represent some of the most explosive events from this volcano, and provide new marker horizons. They are dispersed up to 90 km north-east to east of the edifice. The tephra contain high SiO2 (73-75.5 wt %) glass and subordinate basaltic components, and each represents a distinct magma batch that can be fingerprinted. They form two temporal trends toward less evolved magma compositions, punctuated by a large caldera-forming event at 36 ka. Minor tephra dispersal is also recorded at 17.7 ka, 25 ka, 35 ka and pre-50 ka. The historically 50 th Kaikoura05 -78- Kaikoura 2005
active, andesitic White Island volcano has not widely dispersed tephra, and the oldest primary deposit found is ~20 ka. Five pre-50 ka rhyolite eruptions from an unknown Taupo Volcanic Zone source provide evidence for explosive activity in a time interval poorly documented on-land. The cores demonstrate the patchy and uneven preservation of large magnitude tephra falls caused by local bioturbation and ponding in bathymetrically complex regions. Reworked tephra layers are common and often lack indicative lithological features. Such units could easily be misinterpreted as primary events without micro-beam geochemical analyses of glass shards. POSTER 3-D STRUCTURAL PERMEABILITY IN CONTRACTIONAL SETTINGS R. H. Sibson Dept. of Geology, University of Otago, P.O. Box 56, Dunedin. (rick.sibson*stonebow.otago.ac.nz) Fluid flow in the Earth’s crust is influenced by anisotropic permeability as well as by hydraulic gradients in the crust. 2-D modelling of flow systems based on cross-sections drawn perpendicular to the strike of orogenic belts can be misleading when considering fluid redistribution during contractional orogenesis, because of the tendency to think of flow as restricted to the plane of the section. Topographically driven flow and flow in overpressured systems may both be affected by directional permeability parallel to strike. Bedding anisotropy and other forms of primary rock layering combine with stress/strain-controlled structural permeability, embracing systems of faults and fractures as well as fold closures, foliations, etc. In simple fold-thrust belts associated with accretionary prisms, collisional, and compressional inversion orogens, structural permeability is dominated by fold hinges and duplex structures, plus fault-fracture intersections aligned parallel to strike. In both active and ancient fold-belts, evidence exists for high levels of hydraulic communication extending along fold hingelines for kilometres to tens of kilometres along strike. Where convergence varies along contractional orogenic belts, fluid may thus be expelled laterally along this directional permeability from the regions of most intense shortening. The volume of fluid passing through a cross-strike section is then likely to be far greater than that inferred from considering fluid redistribution restricted to the plane of the section. Along the New Zealand plate boundary, 3-D structural permeability affecting fluid redistribution seems likely to be especially important within the dewatering accretionary prism of the Hikurangi Margin, and in areas of active compressional inversion (e.g. NW Nelson - Taranaki Basin). ORAL ACTIVE CRUSTAL FLUID FLOW AROUND THE NEW ZEALAND PLATE BOUNDARY – A RESEARCH FOCUS FOR THE 21 ST CENTURY R. H. Sibson Dept. of Geology, University of Otago, P.O. Box 56, Dunedin. (rick.sibson*stonebow.otago.ac.nz) Crustal-scale fluid flow is a frontier area in Earth Science, critically relevant to exploration for, and future exploitation of, energy and mineral resources (oil, gas, geothermal power, hydrothermal mineral deposits). The New Zealand plate boundary (NZPB) is a geochemical factory where the interplay of tectonic and magmatic processes promotes fluid redistribution between the atmosphere, continental and oceanic rock assemblages, the ocean water mass, and the deep Earth. The diverse character of the boundary, comprising opposite-facing subduction zones along the Hikurangi and Fiordland Margins linked by an imperfect transform fault system, gives rise to an array of sites where aqueous and hydrocarbon fluids are being actively redistributed within the crust. These include: i. active hydrothermal circulation coupled to magmatism in the Taupo Volcanic Zone (TVZ) (and its northeastward continuation along the Lau-Havre Trough); ii. zones of sediment compaction and compressional ‘squeegee’ deformation with associated fluid loss along the Hikurangi and Fiordland subduction interfaces; iii. areas of ongoing compressional inversion iv. associated with hydrocarbon migration in the Taranaki Basin and in the northwestern and southern South Island; and topography-driven flow in the uplifted Southern Alps and other mountain ranges flanking the linking transform fault system, and around major volcanic edifices. Fluid redistribution is variously driven by topographic relief and precipitation, upwelling mantle and magmatic intrusion leading to convective circulation of hydrothermal fluids, compaction, deformation, and metamorphic dehydration of thick sedimentary sequences, and changes in the regional stress state. While flow in near-surface systems typically occurs under near-hydrostatic fluid pressure (the ‘normal state’), fluids at depth may be structurally compartmentalised and overpressured well above hydrostatic values. 50 th Kaikoura05 -79- Kaikoura 2005
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CHARACTERISATION OF NEW ZEALAND NEP
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myrtaceous. One 20 mm diameter flow
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ange of lower resolution or fragmen
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CRETACEOUS-EOCENE TRANSGRESSION MAR
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consists of a well-developed canyon
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model. The relative position of the
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converts to plate theory. Thus, the
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and on the following morning the mi
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the LGM grass peak. This period of
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offshore west coast to offshore eas
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4 Institut de Recherche pour le Dé
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VEGETATION AND CLIMATE CHANGE AT TH
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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 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: truncating three plutonic suites of
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
Page 97 and 98: The continental shelf of the Povert
Page 99 and 100: 5 Dept. of Mineral Sciences, Smiths
Page 101 and 102: Adams CJ...........................
Page 103 and 104: Naish T............................
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