ABSTRACT: Surficial geology of the Laurentian Channel and the western Grand Banks of Newfoundland

CGRG Bibliography of Canadian Geomorphology
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Abstract

Five surficial formations are identified on the basis of high resolution seismic reflection profiles, side-scan sonograms, echo sounder data, seabed grab samples, piston cores, and bottom photographs: Scotian Shelf-Newfoundland Shelf Drift, Emerald Silt, Sambro Sand, LaHave Clay, and Sable Island Sand and Gravel. Scotian Shelf-Newfoundland Shelf Drift is a poorly sorted till occurring at the base of the surficial succession, and has been deposited beneath a grounded ice sheet that advanced across the continental shelf. An end moraine complex occurs south of Cape Island on the Scotian Shelf and south of the Burin Peninsula, on the western Grand Banks of Newfoundland. It is the easternmost extension of a submarine end moraine system on the Scotian Shelf. Emerald Silt is a proglacial muddy sediment deposited from floating ice and is interbedded with the till at the distal side of the moraines. Sambaro Sand is a sublittoral muddy sand developed below aLate Pleistocene sea-level terrace at 115 m. It is formed by reworking of the till and proglacial sediments. LaHavre Clay is a homogeneous marine mud deposited in the basins and depressions on the shelf. The material was derived from reworking the sediment on the bank and inner shelf areas during the Late Pleistoce-Holocene transgression. Sable Island Sand and Gravel is a transgressive deposit formed by erosion of till and proglacial sediment in depths less than the 115-m depths of the Late Pleistocene terrace. The distribution and stratigraphic relationships of the surficial formations were controlled by an advance of the continental ice sheet across the shelf together with late and postglacial isostatic and eustatic fluctuations. The sediment distributions are mostly relict except in the shallow areas where some reworking of Sable Island Sand and Gravel occurs in response to the modern hydrodynamic regime. All surficial formations have beenscoured by grounded icebergs unlike the Scotian Shelf where iceberg furrows are confined to till surfaces.

Bibliography of Canadian Geomorphology