HR: 17:30h
AN: T14A-07    [Abstracts]
TI: Neotectonics of the McMurdo Sound Region, Antarctica Interpreted From Multibeam Data
AU: * Lawver, L A
EM: lawver@ig.utexas.edu
AF: University of Texas at Austin, 4412 Spicewood Springs Road #600, Austin, TX 78759-8500 United States
AU: Wilson, T J
EM: twilson@mps.ohio-state.edu
AF: Dept. of Geological Sciences, Ohio State University, 125 S. Oval Mall, Columbus, OH 43210 United States
AB: The NBP0401 cruise of {\it RVIB Nathaniel B. Palmer} (Jan-Feb 2004) surveyed the Terror Rift and western Victoria Land Basin (VLB), Antarctica. The very large iceberg B-15, split latitudinally at the end of October 2003 and then split longitudinally in mid-December. These large bergs restricted ice movement out of the VLB and left about half of our proposed study area covered in very thick multi-year ice where multibeam and seismic data collection was impossible. Significant multibeam data were collected in McMurdo Sound between $77\deg$S and $77\deg$40'S from $164\deg$40'W to Ross Island. Approximately 3000 square km of contiguous coverage revealed numerous features indicating significant neotectonism. Lineated submarine volcanic cones and dykes radiating away from Mt. Erebus are common in the eastern side of McMurdo Sound. The western side consists of a shelf and slope with significant glacial deposition cut by submarine channels. The channel draining the Taylor Valley/ Ferrar Glacier is a narrow, steep-walled feature, less than 200 meters wide and 60 meters deep in spots that trends due north, parallel to the shelf before turning northeast into the basin. The unusual direction of the channel is possibly controlled by resistant volcanic features or by older faulting. Transantarctic Mountain parallel faulting at a depth of 500 m is superimposed on the shelf structure. The very linear faulting shows notching by a number of very small incisions perhaps indicating that the uplift is recent. In the deeper portion of the Sound, within the well-defined `flexural moat' surrounding Ross Island, more sinuous submarine channels are found to a depth of 800-850 m, indicating northward directed flow into the basin. In a 15 by 40 km area near $76\deg$S, $176\deg$E, eight nearly circular features up to 5-6 km in diameter and 100+ m high were found. Although the circular shape is suggestive of a magmatic origin, there is no magnetic signature, suggesting that these features are glacial in origin. The features are asymmetrical with the southeastern side being quite steep and the northwestern side gradually sloping to the northwest. The closest analogue for these features is drumlins albeit these are very large. The new bathymetric data will help us to constrain the relative timing of faulting, volcanism, flexural subsidence and glacial erosion/deposition cycles that have shaped the McMurdo Sound region.
DE: 9310 Antarctica
DE: 8109 Continental tectonics--extensional (0905)
DE: 3022 Marine sediments--processes and transport
DE: 1827 Glaciology (1863)
DE: 1625 Geomorphology and weathering (1824, 1886)
SC: Tectonophysics [T]
MN: 2004 AGU Fall Meeting