Abstract: Sedimentation on Antarctic Continental Slope

John B. Anderson, Dennis Kurtz, Fred M. Weaver

Terrigenous sediment supply to the Antarctic continental margin is almost entirely by ice. The degree to which these glacial sediments are sorted and redistributed on the seafloor reflects the relative competence of marine agents far better than in other marine environments, where the initial textural properties of sediments entering the sea are unknown.

Because ice shelves lose their sediment load at or near the grounding line, ice rafting beyond the Antarctic shelf break is minimal. A substantial part of the sediment supply to the continental slope is by mass movement and turbidity currents, the exact mode of transport being largely a function of the extent of floating ice cover in a region. Where the shelf is covered by perennial ice, as in the southern Weddell and Ross Seas, wave and wind-driven circulation and hence sediment movement across the shelf are greatly retarded. The mass-flow deposits which have been cored on the slopes of these areas are barely distinguishable from the poorly sorted glacial sediments from which they are derived. In the eastern Weddell Sea, western Ross Sea, and along the northern side of the Antarctic Peninsula, ice conditions are less severe. In these regions the continental slope is floored by turbidites which reflect greater sediment supply and sorting on the adjacent shelf.

Contour currents redistribute slope sediments and deposit thick sequences of laminated silts and clays. Again, the extent of sea ice cover is important, the intensity of contour-current flow being largely a function of sea-surface wind stress. Where canyons and rises disrupt the slope trend, flow is diverted. Hence the mode of deposition along the slope changes abruptly where there are such irregularities.

The extent of floating ice is also the primary factor controlling biogenic sedimentation on the Antarctic continental slope, for rates of production and dissolution of biogenic material are tied closely to ice cover.

AAPG Search and Discovery Article #90961©1978 AAPG Annual Convention and Exhibition, Oklahoma City, Oklahoma