Mesozoic and Cenozoic structural trends under southern Bering Sea Shelf
Mesozoic rocks exposed near the tip of the Alaska Peninsula form an antiformal structure that flanks the southern side of Bristol Bay basin and that can be traced with geophysical data about 700 km offshore to the vicinity of the Pribilof Islands. Upper Jurassic sandstone and Upper Cretaceous mudstone dredged from the top and flanks of this structure near the islands confirm that Mesozoic rocks extend from the Alaska Peninsula to the Bering sea margin. The southern part of the Bering Sea Shelf is underlain by several large structural basins. These filled basins encompass an offshore area of about 31,000 sq km. Reflection profiles show that the surface of the offshore antiformal structures is an angular unconformity overlain by Cenozoic beds. The downdip trace of the unconformity in Bristol Bay basin is underlain by reflectors paralleling the contact, a relation suggesting that the basin and perhaps other shelf basins may be underlain by ancient Mesozoic depocenters. The bulk of the thick sections in these basins is, however, thought to be mainly Cenozoic in age. Strata in the basins are cut by high-angle growth faults. The faults commonly offset the seafloor, which implies that basin subsidence and filling continue to the present. Shallow-water diatomaceous mudstone of Eocene and Oligocene age dredged from the continental slope near the Pribilof Islands indicates that collapse of the margin and outer shelf basins began by at least early Tertiary time. In Mesozoic time, the Bering margin between Siberia and the Alaska Peninsula (Beringian margin) may have been a zone of either oblique underthrusting or transform motion between the North American and Pacific lithosphere (Kula plate.). This motion may have rifted the edge of the North American plate, resulting in the formation of a series of elongate basins and ridges paralleling the plate edge.
- Research Organization:
- US Geological Survey, Menlo Park, CA
- OSTI ID:
- 6523474
- Journal Information:
- Am. Assoc. Pet. Geol. Bull.; (United States), Journal Name: Am. Assoc. Pet. Geol. Bull.; (United States) Vol. 64:11; ISSN AAPGB
- Country of Publication:
- United States
- Language:
- English
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