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

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geological rates (10 000 years suggesting that previous assertions regarding the low seismic hazard of the Kapiti-Manawatu region may not be substantiated, and needs to be reappraised. The method used here for determining the paleoseismicity of offshore faults has potentially wider applications elsewhere, and in New Zealand has already been applied to normal (e.g., Cape Egmont Fault, Taranaki; offshore Taupo Volcanic Zone, Bay of Plenty), reverse (e.g., North Canterbury shelf; Lachlan Ridge, Hawkes Bay) and strike-slip faults (e.g., Alpine Fault, Fiordland) in the offshore environment. ORAL THE GROWTH OF ANTICLINAL RANGES IN AN ACTIVE FOLD-THRUST BELT, CENTRAL OTAGO, NEW ZEALAND R. Norris 1 ,E.Bennett 2 , J. Youngson 1 , J. Jackson 2 ,G.Raisbeck 3 ,&F.Yiou 3 1 Dept. of Geology, University of Otago, PO Box 56, Dunedin 2 Bullard Laboratories, Dept. of Earth Sciences, Madingley Road, Cambridge, U. K. 3 Centre de Spectrométrie Nucléaire et Spectrométrie de Masse, CNRS, Orsay, France (richard.norris*stonebow.otago.ac.nz) The Otago fold-thrust belt is situated east of the Alpine Fault within the zone of distributed deformation along the Australian–Pacific plate boundary in South Island, New Zealand. Average shortening rates across the belt, based on both longterm geological estimates and on preliminary GPS data, are only 2-3 mm/yr. We have employed a combination of geomorphology, structural geology and cosmogenic isotope dating to determine the style and rate of fault-fold propagation, and the evolution of the topography in the central part of the belt. Cosmogenic 10 Be measurements were made on “sarsen stones”, remnants of silcrete deposits in the Tertiary sediments overlying the basement schist erosion surface. During uplift of the ranges, the surrounding sediments were rapidly stripped, leaving the silcretes behind. Previous work (E. Bennett et al., J. Geophys. Research, v. 110, B02404, doi: 10.1029/2004JB003184, 2005) has shown that 10 Be ages up to 1.3 Ma are not saturated and provide valuable data on the timing of uplift of the underlying ranges. The data strongly support a model of rapid establishment of fault length followed by increase in amplitude and slow tip propagation. The two ridge systems investigated (Raggedy Range– Blackstone Hill and Rough Ridge–North Rough Ridge) have grown since 1.5 Ma, by either rapid lateral propagation and/or early coalescence of shorter segments, before continuing to increase in height with slower tip extension. Two ridges have developed frontal imbricates within 1 Ma of initiation. Initial growth of all the central/east Otago ranges occurred over a short time period with no systematic progression towards the foreland. Continuing activity across the region indicates the whole thrust belt is ‘out-of-sequence’ in terms of classical thrust kinematics. Erosion of the ridges is very slow and they closely reflect tectonic deformation above the underlying fault. Elastic dislocation modelling of the topography of North Rough Ridge indicates an underlying fault dipping north-westwards at 45° or less. The slipping fault modeled extends from a depth of 1-2 km down to at least 10 km. The average spacing of the ranges of 18 km, together with their average length of 45 km, suggests that they most likely extend to the base of the seismogenic zone. The Rough Ridge system of ridges currently forms the drainage divide between streams draining into the Clutha system via the Manuherikia River and streams draining eastwards into the Taieri system. Prior to the growth of these ridges over the last 1.5 Ma, it is likely that the drainage systems were quite different. The resulting major drainage changes may have important ecological effects, for example on the evolution of indigenous fauna. ORAL TUBULAR CARBONATE CONCRETIONS AS CONDUITS FOR METHANE ESCAPE FEEDING SEAFLOOR COLD SEEPS: SOME NORTH ISLAND EXAMPLES S. Nyman 1 ,C.Nelson 1 ,K.Campbell 2 , F. Schellenberg 1,3 ,P.Kamp 1 ,G.Browne 4 , P. King 4 1 Dept. of Earth Sciences, University of Waikato, Private Bag 3105, Hamilton 2 Dept. of Geology, University of Auckland, Private Bag 92019, Auckland 3 Institut für Geologie und Paläontologie, Universität Tübingen, Tübingen, Germany 4 Institute of Geological and Nuclear Sciences, PO Box 30368, Lower Hutt (s.nyman*waikato.ac.nz) Several Cenozoic sedimentary formations in the North Island of New Zealand include locally prominent development of carbonate concretions which exhibit a variety of broadly tubular shapes, and commonly a central conduit that may be empty or filled with sediment or multiple generations of later carbonate cements. Stable oxygen and carbon isotope data suggest that many of the concreting and later cements were sourced primarily from 50 th Kaikoura05 -62- Kaikoura 2005
ascending methane fluids/gases of possible thermogenic origin. Reconnaissance field studies at localities in onland East Coast and Taranaki basins show several similarities in broad geological setting and associated facies (e.g., within upper slope mudstone), but also local differences likely reflecting their tectonic environment, stratigraphic position, and available fluid migration pathways. In some cases there is a clear association of the tubular concretions with overlying paleo-sea floor seep-carbonate deposits, and we suggest they may mark the subsurface plumbing network of cold seep systems. Tubular concretions clearly aligned along joints and fractures in the East Coast Basin demonstrate an intimate relationship between tectonics and seep development. In eastern Taranaki, the presence of dislodged and massemplaced tubular concretions in the axial conglomerates of certain channel facies in slope mudstone suggests a connection between the loci of seep field development and slope failure and canyon cutting on the late Miocene Taranaki margin, possibly influenced by the build up of gas pressures during seep development. Tubular concretions afford an opportunity to investigate the evolution of cold seeps based on ancient examples, and also the linkage between subsurface and surface portions of such a system. Seep field development has implications for the characterization of fluid flow in sedimentary basins, for the global carbon cycle, for exerting biogeochemical influences on marine communities, and for the evaluation of future hydrocarbon resources, recovery, and drilling and production hazards. ORAL NUMERICAL MODELLING OF THE COMPETITION BETWEEN EXTENSION AND CONVECTION IN HYDROTHERMAL SYSTEMS N.H.S. Oliver 1 ,B.E.Hobbs 2 ,J.G.McLellan 1 , &J.S.Cleverley 1 1 School of Earth Sciences, James Cook University, Townsville, Qld, 4811, Australia 2 CSIRO Exploration & Mining, 26 Dick Perry Avenue, Kensington, WA 6151, Australia (nick.oliver*jcu.edu.au) In many upper crustal hydrothermal and geothermal systems, inferences have been made about the combined effects of extensional deformation and thermally-induced circulation. Deepening convection cells during progressive extension in the Irish base metals province were proposed to explain a temporal change in the Pb isotope composition of ores formed near or at the surface (Russell, 1986, Irish Assoc. Econ. Geol.), and faults and fractures appear instrumental in localization or compartmentalization of active geothermal systems in the Rhinegraben, and in the Taupo Volcanic Zone (TVZ, Rowland & Sibson, 2004, Geofluids). Faults in these systems appear to act either as conduits or barriers, and as pathways for near surface fluids to access ‘impermeable’ basement rocks. However, the specific interplay of long-lived fluid convection through permeable rocks, and short-lived fluid pumping along seismically active faults, remains uncertain. We explore here the interactions of thermally and mechanically-induced fluid flow during extension using a fully coupled finite difference code (FLAC). We used generic rift architecture with a blanket of permeable sediments and volcanics on a less permeable rifted basement. Firstly, we applied a basal heat flow and generated stable convection in the cover sequences, and fluid penetrates down into basement with downwelling zones along rift edge faults. However, when we applied extension at strain rates around 5 x 10 -14 /s (similar to those in the TVZ), stable convection cells were rapidly destroyed by fluid flowing towards dilatant sites on faults. When we turned the extension off again, stable convection reappeared, but the localisation of upflow zones in the convection cells was controlled by the former position of structurally-driven upflow. Our results may explain why the main NE-trending part of the TVZ is not associated with thermal upwelling, because in our models the zones of active extension correspond with structurally-driven downflow and perturbation of the convection. We speculate that convective- and mechanically driven fluid flow in extension zones is competitive, rather than coupled. Apparent coupling may be a consequence of perturbation of thermal structure by fault-driven flow, which then controls convection cell patterns once deformation subsides. ORAL GEOLOGY & STRUCTURE OF THE HAUHUNGAROA RANGE, WESTERN TAUPO VOLCANIC ZONE A.G. O’Loan, J.V. Rowland & C.J.N. Wilson Department of Geology, University of Auckland, Private Bag 92019, Auckland (a.oloan*auckland.ac.nz) The Hauhungaroa Range lies on the western boundary of the Taupo Volcanic Zone (TVZ), and comprises a Mesozoic metasedimentary (greywacke) basement block bounded by a SEfacing normal fault scarp, with andesite volcanoes at its northern (Pureora and Titiraupenga) and southern (Hauhungaroa) extremities. The rangeforming Hauhungaroa Fault scarp appears steep and 50 th Kaikoura05 -63- 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
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 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: 3D IMAGING OF THE FORE- AND BACKTHR
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
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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