Abstract

The Phanerozoic tectonic setting of Canada’s Atlantic continental margin provided a framework for post-Paleozoic episodes of rifting, seafloor spreading, and related sedimentation. An orthogonal fracture system that originated in Late Precambrian time and trended approximately northeastward and northwestward dominated the later tectonic patterns. Cambro-Ordovician shelf carbonates and clastic rocks occur between the northeasterly trending Appalachian Geosyncline in the south and the similarly trending Franklinian Geosyncline in the north.

The Ordovician Taconic and the Devonian Acadian Orogenies affected the Appalachian Geosyncline more strongly than the Late Silurian-Early Devonian Caledonian event. Late Devonian-Early Carboniferous strike-slip faults preceded the formation of clastic-filled Carboniferous grabens in the Canadian Atlantic provinces.

The Ellesmerian Orogeny folded the Franklinian Geosyncline in latest Devonian to Early Mississippian time and was followed shortly thereafter by the first subsidence of the Sverdrup Basin in the Arctic Islands.

In the northeastern United States, pre-seafloor spreading tension in Late Triassic time formed northeasterly trending grabens, and was followed in the Early Jurassic (180 Ma) by seafloor spreading off the Scotian Shelf. Spreading along the southern Grand Banks commenced in the Early Cretaceous (115 Ma) northeast of a major transform fault. North of Flemish Cap, spreading commenced in the Late Cretaceous (Turonian, 90 Ma). The Labrador Sea opened between the end of the Cretaceous (75 Ma) and the beginning of the Oligocene (36 Ma), according to Srivastava (1978), leading to early Eurekan tectonism in the Arctic Islands. The Labrador Sea was separated from Baffin Bay by an active transform fault. Spreading in Baffin Bay began in the Late Paleocene (55 Ma), and ceased at the beginning of the Oligocene (36 Ma), when the Greenland Plate collided with the North American Plate, causing the mid-Tertiary Eurekan Orogeny. This strongly overprinted the Ellesmerian trends and terminated the depositional history of the Sverdrup Basin. Subsequently, the Greenland and North American plates, welded together, moved westward with mild tectonism in late Tertiary time, affecting part of the Arctic Islands and perhaps Baffin Bay to northern Labrador.

Six correlatable regional unconformities have been recognized on the shelves and are at the following levels in the stratigraphic column: Lower Jurassic, Lower Cretaceous, mid-Cretaceous, Lower Paleocene, mid-Tertiary and Middle to Late Miocene.