Bottom-current control on sedimentation in the western Bellingshausen Sea, West Antarctica

Abstract

A set of single- and multi-channel seismic reflection profiles provide insights into the younger Cenozoic sedimentation history of the continental rise in the western Bellingshausen Sea, west and north of Peter I Island. This area has been strongly influenced by glacially controlled sediment supply from the continental shelf, interacting with a westward-flowing bottom current. From south to north, the seismic data show changes in the symmetry and structure of a prominent sediment depocentre. Its southernmost sector provides evidence of sediment drift whereas northwards the data show a large channel-levee complex, with a western levee oriented in the opposite direction to that of the drift in the south. This pattern indicates the northward-decreasing influence of a westward-flowing bottom contour current in the study area. Topographic data suggest the morphologic ridges at Peter I Island to be the main features responsible for variable bottom-current influence, these acting as barrier to the bottom current and entrained sedimentary material. West of Peter I Island, the east-orientated Coriolis force remains effective in deflecting the suspended load of the turbidity currents towards the west, thereby promoting growth of the western channel levee. Calculated sediment accumulation rates based on seismic data reveal Depocentre C to consist of younger Cenozoic material supplied by glacial transport and modified by contour currents in the western Bellingshausen Sea. These findings demonstrate that the shape, structure and distribution of sediment mounds and estimates of sediment accumulation rates can be associated to the influence of bottom currents and their long-term evolution in response to tectonic movements, ice-sheet dynamics and deep-water formation.