Prospective and Future Hydrocarbon Provinces of Bering Sea, South of St. Lawrence Island: ABSTRACT

Abstract

The Bering Sea can be divided into three hydrocarbon provinces that coincide approximately with three major geomorphic areas, namely the continental shelf, the slope rise, and the abyssal basin. The significant findings of several recent USGS studies on the regional tectonic framework and hydrocarbon potential of these provinces are summarized. The shelf province is underlain by a continental platform that is extensionally rifted along its outer edge. Mesozoic rocks form the basement complex and thick Mesozoic(?) and Cenozoic sedimentary sections fill the rift basins. Recent evidence documents (1) several deep sedimentary basins within the shelf province, (2) shallow-water Mesozoic and Cenozoic sedimentary rocks from the continental slope, and (3) confirmation of postulated subsidence along the shelf edge. The slope-rise province, which includes the marginal Umnak plateau, delineates the deep-water transition from oceanic to continental crustal rocks. In Mesozoic time, oceanic crust may have collided with continental crust beneath this province. At present, thick (6 to 10 km) accumulations of Cenozoic and Mesozoic(?) sediment End_Page 693------------------------------ on oceanic crust are found throughout the province. Other significant findings include: (1) seismic evidence for underthrusting and for deeply buried folded sedimentary rock at the base of the slope, (2) geologic evidence for 2 to 4 km of differential subsidence, and (3) the discovery of uplifted and deformed Mesozoic(?) oceanic crust beneath Umnak Plateau. The abyssal-basin province lies entirely in water depths greater than 3,000 m and is underlain by (igneous) oceanic crust. This Mesozoic crust may be a piece of trapped oceanic plate that since early Tertiary time has been covered by a 3 to 8 km-thick sedimentary section. Recent observations include the delineation of regionally thick and locally deformed sediment bodies, discovery of numerous velocity-amplitude features (deep-water bright spots), and geologic and geophysical evidence for extensive, potential reservoir beds. End_of_Article - Last_Page 694------------