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

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EXPLORING CONSTRAINTS ON ANTIQUITY OF TERRESTRIAL LIFE IN NEW ZEALAND H.J. Campbell 1 &C.A.Landis 2 1 GNS Science, PO Box 30-368, Lower Hutt, New Zealand 2 Department of Geology, University of Otago, PO Box 56, Dunedin, New Zealand (h.campbell*gns.cri.nz) The New Zealand land surface appears to be less than 25 million years old. It therefore follows that the modern terrestrial biota is not descended from archaic ancestors residing on proto-New Zealand (Zealandia) when it broke away from Gondwana. Rather, it has evolved from accidental arrivals since New Zealand became emergent. For all that, the modern biota is indeed derived from lands of Gondwanan heritage. Our first statement is a bold assertion. It is based on systematic investigation of the geological evidence for ‘islands’ during latest Oligocene to earliest Miocene time. These ‘islands’ were first portrayed by Charles Fleming in 1959 and have subsequently become established in most treatments of New Zealand geological history and paleogeography since formation of the Geological Society 50 years ago. Our studies have shown that the geological evidence for the existence of islands during latest Oligocene to earliest Miocene time is either nonexistent or so wanting that we can confidently conclude that any islands that may have existed were small and short-lived. Here we critically evaluate four inferred mid-Cenozoic islands in: Fiordland, Central Otago, Northwest Nelson and central North Island. As part of this analysis, we have identified eight factors that appear to have influenced paleogeographic map reconstructions. This research has grown from exploration of regional planar surfaces in the New Zealand landscape and particularly the Waipounamu Erosion Surface as expressed in Otago and the Chatham Islands, and is supported by the ChEARS Marsden Project. All available geological evidence suggests that Zealandia broke away from Gondwana c. 85 Ma and then slowly sank 1,000 to 3,000 metres over a period of c. 60 million years, culminating in complete submergence c. 23 Ma (Waitakian). Shortly following this, plate boundary collision became vigorous resulting in tectonic emergence of New Zealand. This process is ongoing. ORAL UNCOVERING THE FACE OF THE EASTERN NEW ZEALAND MARGIN – A VIEW FROM THE OCEAN Lionel Carter 1 & Jarg Pettinga 2 1 NIWA, Private Bag 14-901 Kilbirnie, Wellington, New Zealand 2 University Canterbury, Private Bag 4800, Christchurch, New Zealand (l.carter*niwa.cri.nz) Our knowledge of New Zealand’s eastern margin, including the active Hikurangi and passive Bounty sectors, is surprisingly recent. Even though the broad outlines of these sectors were charted as early as 1910, it was not until 1958 that Hikurangi Trench and Bounty Trough were formally recognized. Being the pre-plate tectonic era, the forces behind these major oceanic forms were unclear. Hikurangi Trench was regarded as either a compressional or tensional feature, whereas Bounty Trough was seen as the consequence of large-scale uplift of the bordering Chatham Rise and Bounty Platform. Marine studies began in earnest in the mid-1960s. Systematic surveys were undertaken by the Navy and government research groups, but more significant was the oceanographic and geophysical transects run by the USNS Eltanin. This network of survey lines provided the first regional view of the eastern margin. Single channel seismic lines, in particular, highlighted the architecture of acoustic basement and sediment fill, as well as prominent morphological features. In Bounty Trough, the discovery of a canyon-channel system hinted at the long-distance transfer of South Island sediment to the deep ocean via turbidity currents. Likewise, the presence of a prominent axial channel and 2kmthick sedimentary fill in southern Hikurangi Trench, indicated similar trench-fill processes supplemented by the mass wasting of trench walls. However, the margin’s place within a plate tectonic model had yet to be appreciated. Intellectual and technological advances of the 1970s started to shift emphasis from descriptive to process-oriented research. The shelf circulation and eustatic oscillations of sea level were shown to be key drivers of Quaternary sedimentation on and off the margin. The imprint of sea level change on a tectonically active seabed was identified on the Hikurangi margin, yielding landmark papers on sequence stratigraphy and sediment mass transport. Industry seismic data, especially that collected on the reconnaissance voyages of MOBIL’s Fred H. Moore, mapped the eastern margin in unprecedented detail. By 1978, results from marine and terrestrial research were sufficient to finally bring New Zealand into the plate tectonic fold; no doubt giving satisfaction to pioneers and early 50 th Kaikoura05 -12- Kaikoura 2005
converts to plate theory. Thus, the foundation was laid for a suite of studies, fuelled by committed scientists and research facilities, and aided by rapidly developing technologies that included deep ocean drilling, satellite navigation, multichannel seismic profiling, remote sensing from space, seabed mapping systems and computer-based facilities to handle the ever-expanding stream of data. It is a measure of these efforts, that eastern margin science has achieved significant international recognition. But that status should not invite complacency. Much of the margin remains untouched. Thus, the scene is set for another 50 years of discovery. ORAL CANTERBURY DRIFTS, SW PACIFIC OCEAN RECORD OF INTERMEDIATE DEPTH WATER FLOWS SINCE 24 MA Robert M. Carter 1 1 Marine Geophysical Laboratory, James Cook University, Townsville (bob.carter*jcu.edu.au) The Canterbury Drifts were deposited in water depths between 400 and 1500 m by northward flowing, cold, intermediate depth water masses - Subantarctic Mode Water (SAMW), Antarctic Intermediate Water (AAIW), and their predecessor current flows. Drift accumulation started at 24 Ma, fed by terrigenous sediment derived from the newly rising Alpine Fault plate boundary in the west, which has built a progradational shelf-slope sediment prism up to 130 km wide at rates of eastward advance of up to 5.4 km/My. These regionally extensive, intermediate-depth sediment drifts can be examined in outcrop (Bluecliffs Silt and younger equivalents), in marine drillcore (ODP Site 1119) and at the modern seabed. The drifts comprise planar-bedded units up to several metres thick. Sand intervals have either reverse graded or sharp, erosive bases and normally graded tops. Bioturbation is moderate and the sands occur within a pervasive background of cm-scale, planar or wispy alternating muddy and sandy silts, consistent with deposition from rhythmically fluctuating bottom currents. In the Plio-Pleistocene, the sand:silt lithological rhythmicity occurs in synchroneity with Milankovitch-scale climate cycling; periods of inferred faster current flow (sand intervals) mostly correspond to warm climatic intervals. The drifts vary in thickness from 300 m near the early Miocene shoreline, where they were accumulating in limited shallow water accommodation, to 2000+ m under the modern shelf edge. Mounded drifts first occur at 15 Ma (Middle Miocene), their appearance perhaps reflecting more vigorous intermediate water flow consequent upon worldwide climatic deterioration between 15 and 13 Ma. A further change from large (more than 10 km wide) to smaller (1-3 km wide) mounded slope drifts occurs at 3.1 Ma, marking further cooling, the inception of discrete SAMW flows, and initiation of the Subantarctic Front. The natural gamma ray record from Site 1119 contains a history since 3.9 Ma of the waxing and waning of the New Zealand mountain ice cap. Back to ~0.7 Ma, this record closely mirrors the climate history of Antarctica, as manifested in the Vostok and EPICA ice cores, at 0.1 to 0.6 ka resolution. Beyond, and back to 3.9 Ma, the gamma record reflects southern mid-latitude ice-volumes, and perhaps Antarctic polar plateau temperature, at a resolution of 1.3 ky. ORAL 50 th Kaikoura05 -13- 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: model. The relative position of 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 and 62: 3D IMAGING OF THE FORE- AND BACKTHR
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ascending methane fluids/gases of p
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THE GRIFFENS ROAD TEPHRAS: VALUABLE
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sideritic concretions that occur in
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with 63.8%, and then [3] with 49.9%
Page 71 and 72:
U-Th-Ra disequilibria data. In part
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landslide tsunami in the past. Rece
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core complex mode, temperature driv
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truncating three plutonic suites of
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active, andesitic White Island volc
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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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