Wednesday, 29 August 2007 - 12:10 PM
3.A.A-7
Mega debris flows deposits in the Western Wilkes Land margin (East Antarctica)
Federica Donda1, Philip E. O' Brien2, Laura De Santis1, Giuliano Brancolini1, and Michele Rebesco3. (1) Geophysics of the Lithosphere, Istituto Nazionale di Oceanografia e di Geofisica Sperimentale (OGS), Borgo Grotta Gigante 42/c-Sgonico, Trieste, Italy, (2) Petroleum and Marine Division, Geoscience Australia, GPO Box 378, Canberra ACT, Australia, (3) Marine Research and Technology, Istituto Nazionale di Oceanografia e di Geofisica Sperimentale (OGS), Borgo Grotta Gigante 42/c-Sgonico, Trieste
Multichannel seismic data collected off Western Wilkes Land (East Antarctica) reveal the occurrence of mega debris flow on the lower slope and rise deposited throughout the Miocene. They appear mostly coeval with widespread slides on the upper slope, that occur above a Bottom Simulating Reflector (BSR), possibly related to the silica diagenetic front. In some areas, debris flow units are separated by thin deposits of well-stratified facies, interpreted as dominant glaciomarine mixed contouritic and distal turbidite deposits. These units would represent weakened layers and could then played a major role in the slope instability. High sedimentation rates, due to large amounts of sediment delivered from a temperate, wet-based ice sheet, constituted a key factor in the sediment failures. The main trigger mechanism would probably has been earthquakes enhanced by isostatic rebound following major ice sheet retreats.