Clay-mineral determinations have been made on the less than 2 µm size fraction of 116 samples of tills and associated terrestrial sediments, surficial marine sediments, and sediment from deep-sea cores from the eastern continental margin of Canada (Baffin Bay to Nova Scotia).

The mineralogy and geographic distribution of clays in surficial sediment largely reflects the distribution of source lithologies and the local origin of the clays; the influence of climate on clay mineralogy is negligible. An illite-chlorite assemblage predominates in sediments from Newfoundland and Labrador and the adjacent inner continental shelf, whereas kaolinite additionally occurs in parts of the Maritime Provinces. In these areas, illite is most abundant in high-grade metamorphic source terrain, chlorite is relatively more common in low-grade metasedimentary and metaigneous terrain, and kaolinite is relatively more common in areas underlain by Carboniferous-Triassic red beds. Marine sediments from Baffin Bay and the outer continental margin of Newfoundland and Labrador contain kaolinite and montmorillonite, in addition to illite and chlorite, which are derived from underlying Mesozoic-Tertiary coastal-plain strata. On the Nova Scotia margin a similar clay-mineral assemblage is derived from both the red beds on land and submerged coastal-plain strata.

Three clay assemblages are recognized in Wisconsin sediments on the outer continental margin off Nova Scotia and the Grand Banks. These are (1) red clay turbidites enriched in kaolinite that were transported down the Laurentian Channel; (2) sandier, more montmorillonitic turbidites supplied to the Scotian Rise, partly from glacial outwash and partly from erosion of coastal-plain strata in the heads of submarine canyons; and (3) clay turbidites on the Grand Banks margin that contain more chlorite and less kaolinite than those on the Scotian Rise–Laurentian Fan. These assemblages show that downslope dispersion of sediment by turbidity currents was the dominant process. Holocene reworking of local glacial drift on the shelf is supplying sediment to the outer margin, but at a lesser rate.

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