The Gulf of St. Lawrence is the largest embayment on the Atlantic Coast of North America between Florida and the Labrador Sea. In this region, surface geology provides the main control for defining four structural units which can be extended into or across the Gulf using published geophysical data and available well control. Prospective beds are found in early, middle, and late Paleozoic formations which in turn overlie Precambrian, Taconic, and Acadian basement. Acadian basement rocks underlying the Maritimes basin, Sydney basin, Fundy basin, etc., are exposed in parts of Nova Scotia, and continue south beneath the great Mesozoic and Tertiary sedimentary wedge of the Scotian basin.

Production has not been obtained in the Anticosti basin, but most Ordovician formations have yielded gas and oil shows. The thick, gently dipping, early Paleozoic section is fairly prospective. Many seeps and shows, but insignificant oil recoveries, come from Devonian formations in the Gaspe fold belt; the Silurian also may be prospective in this structurally complex area. The Cambro-Ordovician section in both the klippe and autochthonous sequences in the western Newfoundland fault belt is prospective; seeps, shows, and very minor oil production have come from Ordovician porous zones. In the Maritimes basin, the presence of one small oil and gas field, many shows and seeps, oil shale and albertite, pronounced structures, and a thick sedimentary section have maintained interest and act vity in this large intermontane basin of Late Devonian to Permian sedimentary rocks. Carboniferous

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sandstones and carbonate rocks provide the best prospects.

Although estimated values for oil and gas in place in these four structural units may be quite large, the Paleozoic age of the sedimentary section, the low grade metamorphism in some parts of the area, the generally poor porosity at depth, and the large area under water where operations are very expensive all reduce considerably the commercial potential.

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