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

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spore-pollen catalogue [http://data.gns.cri.nz/sporepollen]. Our aim is to integrate these with the NPC and FRED databases to provide a single "seamless" system. ORAL QMAP KAIKOURA: THE NEW 1:250 000 GEOLOGICAL MAP OF NORTHEASTERN SOUTH ISLAND M.S. Rattenbury 1 ,D.B.Townsend 1 & M.R. Johnston 2 1 GNS Science, PO Box 30368, Lower Hutt 2 395 Trafalgar St, Nelson, New Zealand 7001 (m.rattenbury*gns.cri.nz) A pre-publication version of the new 1:250 000 geological map of the Kaikoura region is presented. The map covers 18 100 km 2 of northeastern South Island, from northern Canterbury to southern Marlborough, including Kaikoura and parts of Buller and Nelson. The region straddles the Australia-Pacific plate boundary and the prominent Marlborough Fault System, incorporating the Alpine, Awatere, Clarence, and Hope faults amongst others, is a feature of the area. The map significantly refines the location of many of the known active faults and many new traces have been identified. The basement rocks include parts of most New Zealand tectonostratigraphic terranes. North of the Alpine Fault the Buller and Takaka terranes occur in the far northwest of the map and are intruded by the granitic Karamea and Rahu suites. The Median Batholith to the east includes the mafic Rotoroa Complex and the dominantly felsic Tasman Intrusives and Separation Point Suite granite. Closer to the Alpine Fault are relatively restricted outcrops of the Brook Street and Murihiku terranes, and a wider exposure of the Dun Mountain-Maitai and Caples terranes. Southeast of the Alpine Fault, the Torlesse composite terrane dominates the map sheet area comprising greywacke of Rakaia and Pahau terranes in the west and east respectively. The Rakaia rocks of Triassic age are increasingly metamorphosed towards the west, up to greenschist facies, textural zone III schist near the fault. The weakly metamorphosed Late Jurassic-Early Cretaceous Pahau terrane greywacke is generally less structurally deformed than the Rakaia terrane apart from several zones of melange and broken formation. One of these, the Esk Head belt, occurs at the western edge of the Pahau terrane and is structurally discordant to the Rakaia terrane. The Esk Head belt also contains large areas of poorly bedded and structurally discontinuous sandstone. The Late Cretaceous and Tertiary rocks of the region have been unified under a simplified stratigraphic schema using existing, established names. Where space on the map permits, local stratigraphic detail has been preserved to reflect the diversity of multiple depositional basins, particularly for the Late Cretaceous and Miocene rocks. These rocks are predominantly of marine origin but locally significant terrestrial and volcanic rocks occur. Igneous rocks are relatively abundant in the east of the map area. The most conspicuous of these is the Tapuaenuku Igneous Complex, a discrete mafic igneous pluton which intrudes Pahau terrane and is accompanied by an extensive, largely radial dike swarm. Time transgressive units such as the Amuri Limestone are another feature of the sheet. Glacial till and associated outwash gravel in alluvial terraces dominate the widespread Quaternary deposits of the region. Scree, rock glacier and alluvial fan deposits are common in the mountains and raised interglacial beach deposits adjacent to the coast reflect Late Quaternary uplift. Many lakes in the region are dammed by landslide deposits, most of which are attributed to strong earthquake shaking. POSTER SOME LIKE IT HOT! CORE COMPLEX FORMATION IN THE CENTRAL AEGEAN SEA, GREECE, AND POSSIBLE IMPLICATIONS FOR THE PAPAROA CORE COMPLEX IN BULLER, SOUTH ISLAND, NEW ZEALAND Uwe Ring 1 , Klaus Gessner 2 , Stephanie Brichau 3 & Johannes Glodny 4 1 Department Geological Sciences, Canterbury University, Christchurch, New Zealand. 2 School of Earth Sciences, University of Western Australia, Perth, Australia. 3 Department of Geology, University of Kansas, Lawrence, KS 66045, USA. 4 GeoForschungsZentrum Potsdam, 14473 Potsdam, Germany. (uwe.ring*canterbury.ac.nz) Continental extension is very differently expressed and varies from rifting with little extension resolved on slowly displacing high-angle faults through core-complex forma-tion, which in extreme cases may accommodate more than 100 km of displacement with slip rates >10 km/Myr on the master fault. Numerical simulations suggest that the viscosity of the lower crust plays a fundamental role in the mode of continental exten-sion (Wijns et al. 2005). A high viscosity lower crust (and thus a small viscosity con-trast between the ductile lower and the brittle upper crust) during extension favours rift development. A lower strength of the lower crust, due to a low viscosity, favours a core complex mode of continental extension. Within the 50 th Kaikoura05 -74- Kaikoura 2005
core complex mode, temperature driven viscosity variations can determine whether the lower crust flows in a distributed manner or localisation occurs. This may allow a distinction between ‘cold’ or ‘strong’ core complexes and ‘hot’ or ‘weak’ core complexes. The latter develop when the lower crust has a markedly low viscosity. Hot core complexes in numerical simulations are characterized by largescale normal faults with great slip and cooling rates and the de-velopment of an overall symmetric geometry expressed by a relatively late, secondary ductile shear zone with an antithetic movement sense caused by symmetric, plume-like extrusion of the hot and weak lower crust. In nature, hot core complexes may be ex-pressed by extension-related migmatite domes in their footwalls. Most core complexes worldwide appear to belong to the monovergent cold case. We report on a hot core complex exposed on the islands of Naxos and Ios in the Aegean Sea. The Aegean Sea is an example of ongoing continental extension and core complex formation caused by the retreating Hellenic subduction zone. The extension-related migmatite dome on Naxos Island is characterized by cooling rates >100°C/Myr. Low-temperature thermochronology reveals great slip rates of ~10 km/Myr associated with the top-N Naxos detachment, which is the major detachment of the hot core complex. The secondary, antihtetic top-S normal fault is exposed on Ios Island some 40 km south of Naxos. Age data suggest that the top-S shear zone on Ios formed ~2- 5 Myr after the Naxos detachment. These data are consistent with the numerical simulations of hot core complexes. Exhumation of hot footwall material on Ios did not expose magmatites but triggered anatexis in the lower crust producing synextensional S-type granites in the footwall. Naxos and Ios are presently situated in a central position above the retreating Hellenic subduction zone. We argue that asthenospheric flow associated with subduc-tion-zone retreat caused increased heat input in the center of the region affected by subduction-zone retreat causing the anomalous hot conditions on Naxos and Ios. The Paparoa core complex in Buller, South Island, is a symmetric core complex (Tulloch & Kimbrough 1989) suggesting it fits the hot core complex case. High cooling rates of the Buckland granite in the footwall of the Paparoa core complex (Spell et al. 2000) are in line with this interpretation. In addition, the Paparoa core complex should have detachments with slightly different ages, with large displacements and high slip rates. Furthermore, high-grade rocks should occur in the footwall (White et al. 1994) and their peak metamorphism should be of Late Cretaceous age. ORAL PALAEOMAGNETISM OF VOLCANIC ROCKS IN WAITAKERE AND COROMANDEL, AND MIOCENE RECONSTRUCTION OF NEW ZEALAND D.J. Robertson Physics Department, University of Namibia, P/Bag 13301 Windhoek, NAMIBIA. (DJR*unam.na) Samples from 8 sites in the Waitakere Group, located to the west of Auckland, and 8 sites in the Coromandel Group in the Coromandel Peninsula have been studied palaeomagnetically using complete progressive af demagnetisation. The two Groups lie on opposite limbs of a gentle anticline, and the respective formation mean palaeofield directions become more consistent after unfolding is carried out on a regional basis. After unfolding, the palaeofield directions are 346.9°, -62.1°, 26.7° (as declination, inclination and �95) for the Waitakere Group and 347.5°, -57.9°, 14.1° for the Coromandel Group. Comparison of these results with palaeomagnetic data for other parts of New Zealand indicates that, relative to the southeast South Island and Chatham Rise, the Northern North Island has migrated northwards by an amount in the order of 1000 km and rotated by some 12° anticlockwise and since Miocene time. This is consistent with large scale dextral displacement of the Alpine Fault, compression in the Southern Alps and dilatation in the North Island. Anomalous clockwise rotation in the order of 15° to 45° which has been reported for the eastern North Island and Marlborough is attributable to dextral shear deformation in a zone incorporating the Hikurangi Trench system and likely extensions of the Alpine Fault. ORAL GEOCHEMICAL ASPECTS OF THE COROMANDEL VOLCANIC ZONE: TRACE ELEMENT AND RARE EARTH ELEMENT DATA K.A. Robertson 1 , R.M. Briggs 1 , & M.I. Leybourne 2 1 Department of Earth Sciences, University of Waikato, P B 3105, Hamilton. 2 Dept. of Geosciences, University of Texas at Dallas, Richardson, TX, USA (kr48*waikato.ac.nz) Late Cenozoic volcanic activity in the North Island of New Zealand has been attributed to a series of volcanic arcs following the movement of the subduction zone boundary between the Pacific and Indo-Australian plates. The Coromandel Volcanic Zone (CVZ) is one such volcanic arc active from 18 50 th Kaikoura05 -75- 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
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 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: landslide tsunami in the past. Rece
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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