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

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compositions associated with caldera structures along the entire Kermadec arc. Three of the volcanic centres exhibit the full compositional range from basalt to rhyolite, three are basaltandesite, and the remaining two entirely rhyolitic. In contrast to published results for the southern Kermadec arc, there is no evidence for compositional bimodality, with the data set containing sub-equal proportions of basalt, basaltic andesite, andesite, dacite, rhyodacite and rhyolite. Despite the variety of volcanic edifices sampled, all of the volcanic centres yield tight geochemical correlations for major and trace elements, which are interpreted to indicate simple mixing or fractionation processes. There is a suggestion, yet to be fully established with trace element or isotopic modelling, that three of the four southernmost centres, spanning some 200 km of arc-front, are genetically related. ORAL Volcanic Centre Latitude °S SiO2 wt% Minimum Maximum Mean ‘V’ 25.19 47 69 57.4 ‘U’ 25.44 50 71 58.6 Monowai 25.95 49 62 52.9 ‘T’ 26.39 50 73 65.2 ‘S’ 26.81 69 72 71.5 ‘R’ 27.20 72 74 73.3 ‘P’ 27.86 50 65 58.3 ‘O’ 28.59 56 61 57.6 All 47 74 60.4 INCREASED FRESHWATER RUNOFF FROM THE GROWTH OF URBAN AUCKLAND - THE GREATEST CAUSE OF ESTUARINE FAUNAL CHANGE H.R. Grenfell 1 , B.W. Hayward 1 ,A.T.Sabaa 1 , M. Morley 1 & M. Horrocks 2 1 Geomarine Research, 49 Swainston Rd, St Johns, Auckland. 2 Microfossil Research, 31 Mont Le Grand Rd, Mt Eden, Auckland. (h.grenfell*geomarine.org.nz) Microfossils and molluscs from 13 upper Waitemata Harbour and Tamaki Estuary cores provide a record of human impact on sheltered coastal marine to estuarine environments around the fringes of growing Auckland City. Polynesian forest clearance had only minor impact compared with the increasing tempo of changes in European times. Although sedimentation rate has increased there is no consistent trend towards increasing mud or sand. In all sites, marine ostracods and infaunal bivalves were decimated in European times and largely disappear from the record, coincident with increased abundance of large diatoms and thecamoebians. The foraminiferal microfossil record is the most complete and documents a progressive switch from calcareous-dominated faunas to the agglutinate-dominated faunas of today. All observed changes are similar to those documented in transects passing from the marine environment up an estuary and suggest that increased freshwater runoff from the mushrooming urban areas of Auckland city is the primary driver, not sediment or pollutants. This is further supported by the observation that changes occur during late Polynesian to early European times in the upper Waitemata Harbour, versus late European times (post 1950) in the Tamaki Estuary when impervious surfaces increase dramatically. If increased freshwater is indeed the culprit, carrying out remedial measures will be problematic. ORAL VOLCANIC GEOLOGY OF THE ORTON BRADLEY FORMATION S.J. Hampton &J.W.Cole Dept of Geological Sciences, University of Canterbury, Private Bag 4800, Christchurch (sjh163*student.canterbury.ac.nz) The Orton Bradley Formation was deposited during the period 9.5 – 8.6 Ma. It is part of the Mt Herbert Volcanic Group of central Banks Peninsula, Canterbury, which is considered to be the intermediate stage of volcanism between Lyttelton Volcano (11 – 9.7 Ma) and Akaroa Volcano (9.3 – 8 Ma). Prior to the emplacement of the Mt Herbert Volcanic Group, sector collapse occurred on the southeast side of Lyttelton Volcano. This collapse was probably the result of persistent rifting, similar to that of Valle del Bove, Mt Etna. The sector collapse destroyed the existing crater rim, and provided a pathway for renewed / migrating volcanism in central Banks Peninsula. This collapse structure would have produced a large horseshoe-shaped amphitheatre with a hummocky surface, and would have controlled the deposition / emplacement of later volcanic and fluvial activity. The upper sector of the breach contained alluvial fans, and a topographic low, steep source, amphitheatre, which constrained the initial Homestead Lava Member (new name) flows at the base of the Orton Bradley Formation. Mud deposits formed in localised depressions, on top of the topographically controlled lava flows. A period of 50 th Kaikoura05 -32- Kaikoura 2005
hydrovolcanic eruptions then took place to form the Mt Bradley Volcaniclastic Member, a low angle tuff ring formed by both ‘wet’ and ‘dry’ base surges. ‘Wet’ base surges occurred when there was excess water supplied at the vent, whereas ‘dry’ base surges occurred when water was limited, or used in previous eruptions. Magma / water interaction was shallow, promoting rapid chilling and fragmentation. Eruption through a shallow standing body of water is supported by the presence of middle mud deposits, the majority of blocks over bombs, preservation of delicate cuspate edges on glass fragments, large U-shaped channels, and fluvial deposits and erosion surfaces between eruptive packages. Hawaiian style eruptive activity marked the cessation of phreatomagmatic activity, and formed a thin lava flow. This flow blocked drainage, allowing the development of a lake, and formed the upper mud deposits. A second phase of effusive and phreatomagmatic activity then occurred, producing the interfingering Packhorse Lava Member (new name) flows and Tablelands Volcaniclastic Member. Packhorse Lava Member flows overcame the topographic controlled upper sector collapse and flowed further to the southeast. On exiting the steep sided collapse flows fanned out, but were constrained to the east by the growing edifice of Akaroa Volcano. The succession was then capped by Mt Herbert and flank-fed Akaroa lava flows. POSTER EVOLUTION OF THE PALEO-PACIFIC GONDWANA MARGIN: ISOTOPIC CONSTRAINTS FROM WEST ANTARCTIC XENOLITHS M.R. Handler 1 , R.J. Wysoczanski 1 , J.A. Gamble 2 ,V.C.Bennett 3 & J.H. Berg 4 1 Institute for Research on Earth Evolution, JAMSTEC, Kanagawa 237-0061, Japan 2 Dept of Geology, University College Cork, Ireland. 3 RSES, Australian National University, Canberra 0200, Australia. 4 Geology & Environmental Geosciences, Northern Illinois University, USA. (monica*jamstec.go.jp) West Antarctica and eastern Australia formed part of the contiguous Paleo-Pacific Gondwana margin during Late Proterozoic to Mesozoic times. Key aspects of the regional evolution of this margin, including the nature and age of the component terranes, remain contentious due to the poor exposure of crustal sequences resulting from the extensive ice and sedimentary basin cover in West Antarctica and eastern Australia, respectively. Samples of the deep crust and lithospheric mantle are restricted to xenoliths incorporated in the Cenozoic lavas that have been emplaced along much of the length of this margin, and which can preserve unique age and process information that may be valuable in interpreting continent evolution. Earlier work in southeastern Australia in particular, has demonstrated the potential of the Re-Os isotopic system for constraining the timing of events recorded in the lithospheric mantle of the Paleo-Pacific Gondwana margin, with implications for continent structure and evolution (Handler and Bennett, 2001). We will present new Os and Nd isotopic data for lithospheric xenoliths from Marie Byrd Land and Victoria Land, Antarctica, together with previously published Re-Os data and model ages from along the PaleoPacific Gondwana margin in southeastern Australia and central Marie Byrd Land (McBride et al., 1996; Handler and Bennett, 2001; Handler et al., 2003), and discuss their implications for the development of the margin. The results suggest preservation of Proterozoic lithospheric mantle along the sampled length of the margin. Striking observations include: the similarity of the oldest PaleoProterozoic Os model ages found beneath the Delamerian Fold Belt of southeastern Australia and beneath West Antarctica; preservation of a ca. 500 Ma age from central Marie Byrd Land; and the suggestion that a significant melting event may have affected the mantle beneath both southeast Australia and Marie Byrd Land ca. 900 – 1100 Ma. The timing of this speculated MesoProterozoic mantle event(s) coincides with the age of a significant peak in the U-Pb detrital zircon age spectra of the vast turbidite deposits of the Paleo- Pacific Gondwana margin (Wysoczanski and Allibone, 2004). Handler MR and Bennett VC (2001) Tectonics 20: 177- 188. Handler MR, Wysoczanski RJ and Gamble JA (2003) Chemical Geology 196: 131-145. McBride JS, Lambert DD, Greig A and Nicholls IA (1996) Geology 24: 631-634. Wysoczanski RJ and Allibone, AH (2004) Journal of Geology 112: 401-416. ORAL 50 th Kaikoura05 -33- Kaikoura 2005
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: EMPIRICAL SCALING RELATIONS FOR SEI
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 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
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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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