Seismic investigation, Wilkes Basin. New Zealand Antarctic Programme 1993/94 : Event K101

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Bannister, S.C. 1994 Seismic investigation, Wilkes Basin. New Zealand Antarctic Programme 1993/94 : Event K101. Lower Hutt: Institute of Geological & Nuclear Sciences Institute of Geological & Nuclear Sciences science report 94/21 32 + [18] p.

Abstract: The East Antarctic Seismic Traverse (EAST93) was a geophysical traverse designed to image the sedimentary layers under the 3 km thick East Antarctic ice cap. The completed scientific programme involved a multichannel seismic reflection and gravity line, 312 km in length, on the polar plateau from the west side of the Transantarctic Mountains to the margin of the Wilkes subglacial Basin. Using the multichannel seismic data we should be able to map the extent of the Paleozoic-Mesozoic Beacon Group rocks, the presence and extent of any younger Mesozoic-Cenozoic sediments, and the extent of Jurassic dolerite sills beneath the East Antarctic ice cap. The data should (1) provide quantitative constraint for modelling the uplift of the Transantarctic Mountains and the subsidence of the Wilkes Basin, (2) indicate whether the Ferrar dolerite sills and basalts originated from an active mantle plume or whether they were the by-product of rifting and passive upwelling, and (3) help resolve the debate about the climatic conditions and the size of the ice sheet in the Cenozoic, in particular whether parts of East Antarctica were deglaciated for much of the Late Cenzoic. The programme was jointly carried out by the Institute of Geological and Nuclear Sciences, Victoria University of Wellington, United States Geological Survey and Stanford University. The completed traverse was 312 km long, starting 10 km west of the McMurdo Dome ice-core drill site, which is 25 km west of the exposed bedrock of the Transantarctic Mountains (at Lashly Mt), and ending 323 km west of the drill site over the Wilkes sub-glacial Basin. The traverse was located approximately east-west at about 78 degrees S, and 30-50 km north of the Victoria Land traverse (1958-59), the previous geophysical traverse in the Wilkes Basin region. Multichannel digital seismic data were collected using a shot interval of 150 m, with coincident gravity, radar, and magnetic measurements. This seismic recording was carried out using a 60 channel 300 m long multichannel seismic snow streamer. Relative locations and elevations of the entire traverse were measured at 150 m intervals by N.Z. Department of Survey and Land Information, and tied to three absolute GPS locations measured by the United States Geological Survey. Barometer measurements were taken at 450 m intervals along the traverse. The gravity and magnetic data collected during the traverse indicate that the traverse succeeded in reaching the eastern margin of the Wilkes Basin. The details of the stratigraphy will be shown by the high resolution seismic and radar data which are expected to take about 6 months to process. (auth.)