Continental Margin Sedimentation

The Antarctic Sector of the Pacific is bounded on the south by the Antarctic continent, which is the primary source of terrigenous sediment to this region. For this reason, sedimentation on the Antarctic continental margin is discussed in some detail.

Continental Shelf Sedimentation

The Antarctic continental shelf is unique compared to other continental shelves of the world for the following reasons : (1) glaciers flow directly into the sea so that sediment supply is by ice; surface meltwater runoff is presently minimal; (2) it is covered by sea ice for most of the year and large portions of the shelf are covered by perennial sea ice; and (3) it is deep (average 450 m) and has considerable topographic relief.

Prior to the late 1960s, very few sediment samples had been acquired on the Antarctic continental shelf and slope so that the character of sediments there and the processes responsible for these deposits were poorly understood. Since then, there has been a major marine geological programme on the Antarctic continental shelf, mainly as a result of Eltanin and Deep Freeze (U.S.C.G.C. Glacier) cruises. Most of this work has concentrated on the Ross Sea region. The following discussion is therefore based mainly on studies of sediments from this area.

The marine setting of the Ross Sea region includes virtually every kind of glacial terminus, including large ice shelves (the Ross Ice Shelf and Sulzberger Ice Shelf), ice tongues, ice cliffs, outlet glaciers, and valley glaciers which flow directly into the sea, as well as those whose terminus is situated well inland of the coast (the Dry Valleys regions, Fig. 7.1). The Ross Sea therefore provides an ideal setting in which to study glacial marine sedimentation.

Sedimentation The Coastline

Fig. 7.1. Geography, glaciology and bathymetry of the Ross Sea region. Bathymetry in metres.

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