The continental shelf of Labrador and Newfoundland is underlain by several discrete subbasins. On the western margin of the Labrador Sea, north of the east-trending, east-plunging Cartwright arch, the continental shelf is underlain by up to 10 km of Upper Cretaceous to upper Tertiary marine clastics that constitute the Hopedale-Saglek basin. These sediments overlie a narrow rifted basin of early to middle Cretaceous age, informally called the Erik graben.

Further south, between the Cartwright arch and the axis of the Avalon uplift, the continental shelf is more complex. This region contains the St. Anthony basin, an Appalachian successor basin with upper Paleozoic coal measures and red clastics; the somewhat sinuous, generally northeast-southwest trending Avalon basin containing mixed facies of Mesozoic and Tertiary age; and an unnamed, early Tertiary depocenter having a NNW-SSE trend which is infilled with mostly fine-grained marine clastic rocks.

Hydrocarbon occurrences discovered can be explained in terms of the nature and thermal maturity of probable source rocks and the time of trap formation. Liquid hydrocarbons have only been found in significant amounts in the Avalon basin where traps are supra-adjacent to mature Upper Jurassic source rocks. However, in this basin Lower Cretaceous deltaic sequences can be expected to generate gas. In the remaining basins the sequences contain organic matter that is largely terrestrial and/or at a low level of thermal maturity. In these basins, a low potential for gas is likely.

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