ABSTRACT

Over 300 m of Quaternary sediments are preserved on the Sable Island Bank section of the Scotian Shelf off Atlantic Canada. Most of these are interpreted as Pleistocene glacial sediments. However, a Holocene sandbody over 50 km long, 4 km wide, and 50 m thick occupies the Sable Island topographic high in the center of the bank. This Holocene sandbody is interpreted as having formed from reworking by marine transgression of the underlying Pleistocene glacial and glaciofluvial sediments. During transgression, a subaerial barrier system migrated northward across the bank, leaving behind an extensive set of shoreface-detached ridges. At the margin of the barrier system, longshore transport produced a submarine spit complex that migrated northward with the barrier system but did not produce significant ridge-type shelf sands. Sable Island Bank illustrates the importance of sea level transgression as a major mechanism for supplying sand-sized sediments to the shelf environment. In this case, the sediments have been transported over 100 km to the outer shelf by glacial and fluvial processes during low sea level stands. In addition, Sable Island Bank illustrates the importance of paleotopography in generating potential stratigraphic traps in shelf sandbodies. Topographic relief is likely to be generated on continental shelves exposed during low sea levels. During subsequent transgressions, sandsized sediments are produced by reworking and are stranded on isolated topographic highs.

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