Sedimentary processes across the continental rise of the southern Antarctic Peninsula

Abstract

A series of large sediment mounds have been identified along the Pacific portion of the Antarctic Peninsula continental rise. These mounds are composed of sediment delivered to the continental rise during the advance and retreat of grounded ice across the shelf. The stratigraphic development of one of these sediment deposits, the Tula sediment mound, is examined to investigate how the onset of glaciation influenced the deep-sea depositional environment along this portion of the margin. The stratal relationships, associated facies distribution, and the physiography observed along the southern Antarctic margin reflect the waxing and waning of the Antarctic ice sheets; various processes erode, transport, and deposit sediment along the outer shelf, slope, and rise throughout a glacial cycle. A deep-sea erosional unconformity is apparent at the base of the Tula deposit. This surface may reflect the first onset of intensified bottom water circulation along the margin perhaps induced by the tectonic opening of the Drake Passage. The Tula sediment mound is comprised predominantly of canyon/overbank systems. Evidence for the onset of canyon cutting and the development of the thick overbank deposits (> 2 km) is found immediately above the deep-sea erosional unconformity. Relating increased canyon cutting across the continental rise to the fluctuation of ice across the shelf implies that the onset of predominantly glacial conditions commenced soon after the onset of intensified bottom water circulation along this margin. The volume of sediment associated with the Tula deposit and the apparent ‘point source’ distribution of the channel systems suggests that much sediment was transported to the slope and rise perhaps by meltwater processes through these canyons.