Abstract

A study of processed seismic reflection profiles along the eastern Canadian continental margin indicates the occurrence at depth of paleocontinental slopes of Cenozoic–Mesozoic age, generally in the vicinity of the present continental slope. The paleoslopes are of two general types, constructional and destructional, formed respectively by progradational processes and mass wasting. The inclined beds of the progradational sequence (clinoform beds) represent the constructional slopes and were probably formed at times when deposition was simultaneous on the shelf, slope, and rise. Conditions leading to the establishment of a relatively deep shelf edge would favor constructional slope formation and preservation. A relatively shallow shelf edge, common during times of low sea level, would promote cutback at the shelf edge and upper slope and lead to the formation of destructional slopes. The depth of the shelf edge is mainly established by the balance between rates of sedimentation and subsidence in conjunction with the processes arising from variations in sea level.The sequence of constructional and destructional paleocontinental slopes varies widely along the Canadian Atlantic margin. On the western Scotian Shelf adjacent to the LaHave Platform the paleoslopes are mainly destructional and are in proximity, with only fragmental expression of former constructional slopes remaining. On the eastern Scotian Shelf and Grand Banks destructional paleoslopes are widely spaced in section between thick areas of constructional slope development. Paleoslopes along the northeast Newfoundland and Labrador Shelves are mainly constructional. The differences may be related to age of opening of the Atlantic Basin.The type and distribution of paleocontinental slopes along a margin could influence the migration of hydrocarbons from the eugeocline to the miogeocline.

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