In Quebec, the Atlantic Provinces, and adjacent offshore areas almost all systems are represented. Gas and/or oil shows have been reported from Ordovician, Devonian, Carboniferous, late Mesozoic, and Tertiary rocks. The only commercial production of oil and gas is from a fluviolacustrine sequence in the lower Carboniferous near Moncton, New Brunswick.

In recent years the search for petroleum has expanded to include the Gulf of St. Lawrence, most of the continental shelf, and part of the slope. Offshore geophysical surveys indicate sedimentary thicknesses of 20,000 ft on the outer Labrador shelf, 24,000 ft in the Gulf of St. Lawrence, 20,000 ft on the Scotian shelf, and 18,000 ft on the Grand Banks of Newfoundland.

On the Scotian shelf, shallow drillholes, grab samples, and a 15,106-ft well indicate the presence of Quaternary, Tertiary, and Cretaceous sedimentary strata. On Grand Banks, two holes penetrated Tertiary and Cretaceous strata. One well was abandoned in salt at 4,834 ft and the other at 5,250 ft in siltstone. From 1963 to 1969 the petroleum industry has conducted more than 150 crew-months of geologic and geophysical offshore exploration in Eastern Canada.