Late Neogene to Recent seafloor instability on the deep Pacific margin of the Antarctic Peninsula

In this study we document evidence of sediment mass transport from swath bathymetry and multichannel seismic reflection data in the Pacific margin of the Antarctic Peninsula. The present setting of this margin is strongly influenced by its peculiar tectonic and sedimentary evolution, which reflects the passage from an active to a passive margin , and the transition from river–dominated to glacial-dominated sedimentation. Contouritic sedimentation persists throughout the late Neogene only on the continental rise, while rapid progradation of steep wedges composed of glacial diamicton occurs on the slope. Other than minor erosional gullies on the upper slope, there is no evidence of major incisions such as channels, canyons, or slide scars on a continental slope that averages 13° dip . We intrepret this situation as resulting from the high-shear strength of the slope-forming diamicton delivered by grounded ice-sheets. The main transport process of sediment to the slope were short-run debris flows. Turbidity currents most likely originated by the down-slope evolution of debris flows, and were able to generate large deepsea channel systems that were generated at the base of the continental slope. On the continental rise, the relatively good sorting and high accumulation rate of sediments forming sediment drifts favoured slope failure even on gentle slopes. Coalescent head scarps that form the drift crest were produced by the undercutting of the steeper flanks of the drifts that form the walls of the turbudity channels flowing in the low relief between the drifts. Failure along stratal weak layers at the gentle side of sediment drifts produced either relatively small, concave slide scars in the margin-proximal drift or long rectilinear scars in distal locations. Gravitational instability on the continental rise is thought to relate to the physical properties of contouritic sediments deposited in this high latitude setting.