The Labrador Shelf is dissected by the Marginal Trough into a narrow inner rocky shelf, which is the submerged extension of the Precambrian Shield landmass, and an outer shelf zone consisting of broad, flat banks mantled by thick deposits of glacial drift. The inner shelf north of Groswater Bay is 35 km wide, with a highly irregular bedrock-dominated bottom topography. Unconsolidated materials consist of sand, and coarse gravel "pavement" deposits. Sand deposits are less than 1 m thick and limited in areal extent to the flat-bottomed, low-lying areas between bedrock highs. Coarse gravel deposits occur as veneer pavements on the flanks of highs. The sands are underlain either by cohesive muds (early Holocene?) which were deposited in former basinal depressions, or by coars gravels in local areas marginal to bedrock outcrops. The coarse gravels are probably relict lag deposits formed by the reworking of glacial drift, but the sands are thought to be derived from contemporary nearshore and beach sediments situated about 10 km west of the study area.

The thin and patchy sand distribution suggests that transport mechanisms are more than sufficient to disperse the volume of sand that is being supplied to the inner shelf. Preliminary analysis of near-bottom velocity measurements indicates that the seabed is subjected to a strong southeasterly current (Labrador current) which induces a net southeasterly sand flux across the shelf. The predominantly resistant substrate of the shelf would likely be swept clean of sand, if it were not for the irregular bottom configuration which provides local and temporary sinks for sand deposition.

The most important sediment-transport process on the inner shelf is the southeasterly directed Labrador current. Wave-generated currents are of lesser importance (except in shallow nearshore areas) as a sand-dispersal mechanism, and iceberg-scouring is more effective in redistributing sediment in areas seaward of the inner shelf edge.

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