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Abstract: Multichannel seismic data collected off Western Wilkes Land (East Antarctica) reveal widespread sediment mass movement events, mainly in the form of mega debris flows deposited on the continental rise. In places, they have a seaward extent of more than 200 km and a thickness of up to 400 m. Debris flow units are commonly separated by thin deposits of well-stratified facies, interpreted as glaciomarine mixed contouritic and distal turbidite deposits, possibly with some hemipelagic sediments. These units, due to a dominant contouritic component, represent weakened layers and could then play a major role in the slope instability. Based on stratigraphic correlation with DSDP Site 268, it is suggested that slope failures in the Western Wilkes Land occurred mostly during the Miocene. Inferred high sedimentation rates, due to large amounts of sediment delivered from a temperate, wet-based ice sheet, would have constituted a key factor in the sediment failures. The distribution of mass wasting-related features appears also strongly related to the amount of meltwater discharge. The main trigger mechanism would probably have been earthquakes, enhanced by isostatic rebounds following major ice sheet retreats. [Copyright &y& Elsevier]

The continental slope and rise seaward of the Totten Glacier and the Sabrina Coast, East Antarctica features continental margin depositional systems with high sediment input and consistent along-slope current activity. Understanding their genesis is a necessary step in interpreting the paleoenvironmental records they contain. Geomorphic mapping using a systematic multibeam survey shows variations in the roles of downslope and along slope sediment transport influenced by broad-scale topography and oceanography. The study area contains two areas with distinct geomorphology. Canyons in the eastern part of the area have concave thalwegs, are linked to the shelf edge and upper slope and show signs of erosion and deposition along their beds suggesting cycles of activity controlled by climate cycles. Ridges between these canyons are asymmetric with crests close to the west bank of adjacent canyons and are mostly formed by westward advection of fine sediment lofted from turbidity currents and deposition of hemipelagic sediment. They can be thought of as giant levee deposits. The ridges in the western part of the area have more gently sloping eastern flanks and rise to shallower depths than those in the east. The major canyon in the western part of the area is unusual in having a convex thalweg; it is likely fed predominantly by mass movement from the flanks of the adjacent ridges with less sediment input from the shelf edge. The western ridges formed by accretion of suspended sediment moving along the margin as a broad plume in response to local oceanography supplemented with detritus originating from the Totten Glacier. This contrasts with interpretations of similar ridges described from other parts of Antarctica which emphasise sediment input from canyons immediately up-current. The overall geomorphology of the Sabrina Coast slope is part of a continuum of mixed contourite-turbidite systems identified on glaciated margins. • The slope and rise off the Totten Glacier feature sediment ridges between submarine canyons. • Sediment ridges in the east are formed from turbidity currents flowing in adjacent canyons and a pelagic component. • In the west, larger ridges are formed from widespread hemipelagic and contouritic sedimentation. • The western ridges are separated by a submarine canyon with a convex thalweg mostly sourced from the ridge flanks. [ABSTRACT FROM AUTHOR]