Abstract

A submarine end-moraine complex occurs on the Scotian Shelf south and east of Halifax at 30 to 40 km offshore. It extends as a belt of low ridges which lies parallel to the present coast. Some of the larger individual ridges extend up to 55 km in length, with a slight arcuate pattern, and are an average of 50 m in height above the underlying bedrock. The full extent of the system has not been determined; however, a cursory examination indicates its occurrence along at least 500 km of the coast, in water depths ranging from 70 to 200 m.

The moraine pattern is not revealed on the published bathymetric chart, because the ridges are to a large degree sub-bottom features, masked by ponded clay and silt deposits. However, the extreme peaks of some ridges may crop out slightly above the clay and silt of the bottom, so that their pattern must be resolved by detailed geologic mapping. The materials forming the exposed portions of the ridges range from relatively unaltered to completely reworked glacial debris, depending on the depth of water in which they occur.

Resolution of the moraine pattern is greatly enhanced when the ridges are mapped as sub-bottom features, using high-frequency echograms obtained at closely spaced intervals. The degree of penetration with such an echo-sounder is limited essentially to the base of the clay, but the full profile of the moraines above the underlying bedrock is revealed by low-frequency, continuous seismic reflection profiles.

Sub-bottom records and textural data on bottom samples indicate the occurrence of stratified proglacial deposits associated with the moraines.

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