Abstract

Geologically, the Atlantic margin of the United States has been one of the most extensively studied regions of the world, with one exception — no hydrocarbon exploration tests have been drilled offshore.

Major structural and depositional features of the margin reflect a history of continental rifting in the Triassic, seafloor spreading beginning in Early Jurassic, and large-scale subsidence in later Mesozoic and Cenozoic time. A magnetic feature known as the Slope Anomaly approximates the continental/oceanic crustal boundary. A series of depositional maxima located along this feature form a composite Atlantic margin trough.

The stratigraphic section of the trough consists of an areally expanding sequence of Jurassic through Cretaceous beds overlain by thinner Cenozoic units. Beneath the shelf and coastal plain this sedimentary prism rests primarily on Paleozoic metamorphic and igneous rocks. However, Triassic taphrogenic deposits and smaller areas of unmetamorphosed Paleozoic sediments also are found beneath the unconformity.

Three prospective offshore areas along the margin include: (1) Georges Bank with up to 8 kilometers of sediment, (2) Salisbury Embayment with more than 12 kilometers of sediment, and (3) the Southeast Georgia Embayment and its extension beneath the Blake Plateau with nearly 10 kilometers of sedimentary section.

Published estimates of potentially recoverable hydrocarbons for the U.S. Atlantic margin vary greatly. In 1970 a National Petroleum Council study group estimated 12 billion barrels of petroleum liquids and 67 trillion cubic feet of gas for the shelf and slope north of Florida. The most optimistic estimate of 48 billion barrels of petroleum liquids and 220 trillion cubic feet of gas for the Atlantic offshore area was made by the U.S.G.S. In any case, the U.S. Atlantic continental margin promises to be a major petroleum-producing province.