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Gravel-barrier migration and overstepping

Marine Geology
Publication Date
DOI: 10.1016/0025-3227(91)90122-k


Abstract Despite the widespread occurrence of gravel barriers on mid- to high-latitude coasts, understanding of their stability and relationship to gravel deposits on the inner continental shelf remains rudimentary. On sand-dominated coasts subject to rising relative sea level, barrier overstepping has been postulated as a mechanism for preservation of beach deposits on the shelf, but direct observation of overstepping events has been lacking. Observations at a site on the Atlantic coast of Canada reveal migration of a gravel barrier at 8 m a −1 landward over back-barrier mud, following abandonment of part of the barrier volume on the shoreface. This provides clear evidence for overstepping and suggests that it may play a role in the formation of inner-shelf gravel deposits. Integrity of the migrating (stretching) barrier depends on continued sediment supply from the headland source to a connecting ridge, which must become progressively longer as the landward displacement of the barrier increases.

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