HR: 1340h
AN: B33C-0270    [Abstracts]
TI: How Big is Bedout?
AU: * Nicholson, C
EM: craig@crustal.ucsb.edu
AF: Marine Science Institute and Institute for Crustal Studies, University of California, Santa Barbara, CA 93106-6150 United States
AU: Goncharov, A
AF: Geoscience Australia, GPO Box 378, Canberra, ACT 2601 Australia
AU: Lockwood, A
AF: Geological Survey of Western Australia, 100 Plain Street, East Perth, 6004 Australia
AU: Nakamura, Y
AF: Institute for Geophysics, University of Texas, Austin, TX 78759-8500 United States
AU: Wilson, D S
AF: Marine Science Institute and Institute for Crustal Studies, University of California, Santa Barbara, CA 93106-6150 United States
AU: Becker, L
AF: Marine Science Institute and Institute for Crustal Studies, University of California, Santa Barbara, CA 93106-6150 United States
AB: Based on analyses of recovered core material, the Bedout High, located on the Northwest Shelf of Australia, has been proposed as the central uplift of a large, buried complex impact crater of end-Permian age. A major factor in assessing its possible contribution to the Permian-Triassic mass extinction and other end-Permian events is its estimated size. Although geophysical data alone cannot resolve its origin, initial analyses of regional gravity and magnetic data, together with seismic reflection and refraction surveys, indicate that the Bedout structure is at least as large as Chicxulub, or about 200 km in diameter. Comparison of the diameter of the central uplift (40$-$60 km), the vertical extent (or structural relief) of the central uplift (6$-$7 km), and the diameter of the inferred primary collapse (or transient) crater ($\sim$90$-$100 km) are all of equal or larger dimensions. Further details of crater morphology and maximum crater diameter are less well resolved at Bedout owing to its greater depth of burial ($>$3 km), its greater age ($\sim$250 Ma) and subsequent overprint, and the resolution capability of the currently available data. The estimated size, age and location of the Bedout structure, however, are consistent with the known distribution of end-Permian impact debris found worldwide. Additional multidisciplinary studies, including aeromagnetic and gravity surveys, 3D wide-angle reflection and refraction experiments, drilling, and additional core analyses are needed to further verify the inferred impact origin of Bedout, and to better refine estimates of crater size and 3D geometry.
UR: http://beckeraustralia.crustal.ucsb.edu
DE: 5420 Impact phenomena (includes cratering)
DE: 3005 Geomagnetism (1550)
DE: 3010 Gravity
DE: 3025 Marine seismics (0935)
DE: 1630 Impact phenomena
SC: Biogeosciences [B]
MN: 2004 AGU Fall Meeting