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

More documents

Recommendations

Info

indication of the style or extent of Antarctic glaciation. Therefore further drilling was planned both through DSDP in other parts of the Antarctic margin (Antarctic Peninsula and Prydz Bay) and through the use of a land-based drilling system from the fast ice of McMurdo Sound, where NZ-led efforts had identified a sedimentary basin suitable for drilling close to the edge of the Transantarctic Mountains (and the East Antarctic ice sheet). This drilling (www.geo.vuw.ac.nz/croberts ), along with recent high-resolution deep-sea isotope records, has now led to the following history. Around 34 Ma an ice sheet reaches the coast on both sides of Antarctica. Subsequent ice sheets advanced and retreated on Milankovitch frequencies, causing variations in eustatic sea level of the order of 50 m through Oligocene and early Miocene times. Low beech forest persisted around the coast throughout this period. • Around 14 Ma the ice sheet developed a • persistent core with margins close to its present limits and largely frozen to its bed. During the warm Pliocene coastal Antarctica was warmer by several degrees, but there is no firm evidence that the East Antarctic ice sheet collapsed. From 2.5 Ma to the present the Antarctic ice sheet has responded to sea level variations induced by Northern Hemisphere ice sheets, but only on a scale of ~15 m of sea level equivalent. • Future drilling by the ANDRILL consortium will investigate Quaternary behaviour of the Ross Ice Shelf, and Antarctic climate during the middle Miocene transition, in the McMurdo area (http://andrill.org/ ). ORAL THE CAPE ROBERTS PROJECT: TECTONIC AND CLIMATIC HISTORY OF THE VICTORIA LAND COAST, ANTARCTICA OVER THE LAST 34 MA. P. J. Barrett 1 & Cape Roberts Science Team 2 1 Antarctic Research Centre, Victoria University of Wellington, P.O. Box 600, Wellington. 2 55 scientists from Italy, United States, New Zealand, Germany Australia, United Kingdom and The Netherlands) (peter.barrett*vuw.ac.nz) From 1997 to 1999 the Cape Roberts Project (http/www.geo.vuw.ac.nz/croberts) drilled 3 holes off the Victoria Land coast at 77.0ºS and 163.7ºE. The project was a cooperative venture between scientists, administrators and Antarctic support personnel from 7 countries. The aim was to investigate the early history of the East Antarctic ice sheet and the West Antarctic Rift System, using a 55 tonne drilling system set up 13 to 16 km offshore on fast sea ice. Water depths ranged from 153 m to 295 m and core recovery for the 1680 m drilled was 95%. The cores are a high quality nearshore marine sedimentary record for the period from 17 to 34 Ma ago and are well-dated from volcanic ash, biostratigraphy, Sr isotopes and magnetostratigraphy. Key findings are: i. Provenance studies indicate the Transantarctic Mountains had achieved most of their present height by 34 Ma. Apatite fission track studies show Cenozoic denudation began at ~55 Ma, but CRP core studies show that most of the 1500 m of subsidence on the western margin of the Victoria Land Basin took place from 34 to 29 Ma, slowing down to almost none by 17 Ma, and none since that time (Wilson et al., Geology, submitted). This changes the established view of the West Antarctic Rift System. ii. The stratigraphy is largely cyclic repetitions of shallow glacimarine facies, with well-dated cycles of glacial advance and retreat around 24 Ma showing that the Antarctic ice sheet iii. responded to orbital forcing at that time, much as the Northern Hemisphere ice sheets have done in the Quaternary (Naish et al., Nature, 2001). Pollen records show the cooling of the Victoria Land coast from a temperate climate (>34 Ma) to a cool temperate climate (34 to ~17 Ma) (Prebble et al, Palaeogeography, Palaeoclimatology, Palaeoecology, in press). This record shows no hint of the late Oligocene warming inferred from deep-sea isotopes by Zachos et al (Science, 2001). An alternative explanation for the apparent warming has now been provided by Pekar et al (Palaeogeography, Palaeoclimatology, Palaeoecology, in press). iv. Rapid sedimentation and multiple dating v. techniques on CRP core have provided a new potential calibration point for the Oligocene- Miocene boundary at 23.7 Ma (Wilson et al., Geology, 2002). A 2-m-thick shell bed within 43 m of Quaternary strata in CRP-1, and dated at 1.1 Ma, records a “super-interglacial” period (MIS 31) when the Antarctic coast was ice-free and significantly warmer than today (Scherer et al., Nature, in review). Detailed results from individual drill holes can be found in 10 issues of the journal Terra Antartica between 1998 and 2001. POSTER 50 th Kaikoura05 -6- Kaikoura 2005
CRETACEOUS-EOCENE TRANSGRESSION MARKED BY CHANGES IN SEDIMENT PROVENANCE AND GLAUCONITE FORMATION, BROKEN RIVER TO WAIPARA/IRONCREEK FORMATIONS Kari Bassett & David Kapoutsos Dept. of Geological Sciences, University of Canterbury (kari.bassett*canterbury.ac.nz) Detailed provenance analysis and glauconite morphology of the Broken River and overlying Ironcreek/Waipara greensand Formations were conducted at 4 localities: the Mandamus-Dove River confluence, Waipara River, Avoca, and Castle Hill basin. The basal Broken River Formation is a fluvial boulder conglomerate interbedded with sandstones, mudstones, and coal dated as Haumurian (L. Cretaceous) by pollen. The transgressionismarkedbyagradualdrowningof the fluvial conglomerates with glauconite appearing in the beds immediately overlying the conglomerates in all localities. These estuary deposits contain a mixture of nascent, micaceous, and evolved/mature types of glaucony, previously described as Types A and B by McConchie and Lewis (1978). In transgressive successions, glauconitization commonly post–dates coarse grained sedimentation in nearshore areas. Upsection, evolved/mature glaucony dominates, in some beds formed in situ (autochthonous) and in other beds transported from nearby (paraautochthonous) to line foresets. The age of the greensand units is Mangaorapan - Whaingaroan (Early Eocene Late Eocene). The extremely low sedimentation rate from Cretaceous to Eocene is necessary to form the evolved/mature type of glauconite. Clast counts from the basal conglomerates indicate derivation from very local sources, the underlying Torlesse greywackes and/or the Mandamus Igneous Complex. Quartzose sandstones plot in the interior craton province in QFL plots for both Broken River and Waipara/Ironcreek Formations. Sandstone lithics are probably derived from Torlesse greywacke. Alkali feldspars dominate over plagioclase indicating a probable felsic plutonic source. SEM-cathodoluminescence on quartz grains indicates a mixture of plutonic and metamorphic quartz with minor volcanic input. Plutonic grains are identified by microcracking features, and are possibly derived from western Province batholiths such as the Karamea or Separation Point Batholiths. Polycrystalline/dark CL quartz grains indicate a relative high-grade metamorphic source such as the Haast/Otago Schist, while dark CL monocrystalline quartz grains indicate a low to medium metamorphic grade, possibly the Alpine schist, Otago Schist, or Greenland Group. Volcanic quartz is zoned with straight extinction and was most likely derived from the Cretaceous Mt Somers rhyolites and not the underlying Mandamus Igneous Complex due to a lack of coarse quartz crystals. The provenance analysis suggests local derivation of sediments while fluvial deposition occurred followed by more distal derivation once transported in the nearshore marine setting. The glauconite analysis indicates extremely low sedimentation rates with autochthonous/para-autochthonous glaucony formation in nearshore marine settings, possibly even estuary environments. POSTER SEDIMENTOLOGY OF THE MAHOENUI GROUP, KING COUNTRY REGION T. Bear, P.J.J. Kamp & C.S. Nelson Department of Earth Sciences, University of Waikato, Private Bag 3105, Hamilton. (tlkb2*waikato.ac.nz) The Mahoenui Group is of Early Miocene age (Otaian Stage) and accumulated in the King Country region of western North Island. It represents a discrete depocentre that formed during the early Otaian and became structurally inverted during the late Otaian or early Altonian. The present area of outcrop is probably less than the original extent of the depocentre, as its southern margin is buried beneath younger formations, and its eastern margin is erosionally truncated within the Hauhangaroa Range. The western margin was bounded by the Tongaporutu-Herangi structural high, which was being deformed (uplifted) during sedimentation. The Mahoenui Group conformably overlies the Oligocene Te Kuiti Group in the northern and eastern parts of the basin where this contact is exposed, and marks dramatic and sudden deepening from shelfal to bathyal depths, corresponding to a lithological change from carbonate to siliciclastic sediments. Mahoenui Group is unconformably overlain by late Early Miocene (Altonian) Mokau Group in the north and west, and by the middle Miocene (Lillburnian) Otunui Formation in the south and east. Mahoenui Group comprises a flysch succession in the south (Taumarunui Formation) and a massive mudstone facies in the north (Taumatamaire Formation). Facies analysis of the Taumarunui Formation confirms earlier oil company investigations that it comprises turbidities and intervening hemipelagic mudstone, that would have accumulated as broad submarine fan deposits at bathyal depths. The scale of the fans is larger than the largest of the outcrops, some of which are hundreds of metres long. Surprisingly, there is no evidence of a regressive shelf or slope succession at 50 th Kaikoura05 -7- Kaikoura 2005
Page 1 and 2: CHARACTERISATION OF NEW ZEALAND NEP
Page 3 and 4: myrtaceous. One 20 mm diameter flow
Page 5: ange of lower resolution or fragmen
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 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 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............................
show all

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

Create successful ePaper yourself

Delete template?

Save as template?