Regional geological and geophysical relations support the notion that the basement of the Aleutian basin of the Bering Sea is a far-traveled terrane of oceanic crust. This terrane--named Aleutia--is probably a fragment of Pacific lithosphere (Kula plate?) that formed at an equatorial spreading center in the Early Cretaceous. Aleutia arrived in the Aleutian-Bering Sea region about 55 Ma and was accreted to the Alaskan-Siberian continental margin when a long-established subduction zone located there was abandoned and shifted southward to the present offshore position of the Aleutian Arc. Formation of the arc entrapped Aleutia in the Bering Sea and thereby formed the Aleutian basin, which has since accumulated a geosynclinally massive overlap assemblage of rise-prism and bas n-plain deposits as thick as 12 km.

The capture concept of Aleutia introduces two speculative circumstances relevant to assessing the resource potential of the Aleutian basin. First, the likelihood that in the middle Cretaceous its relatively shallow submerged basement resided near an equatorial spreading center implies that younger basin-plain deposits of the overlap assemblage may have accumulated above oceanic pelagic beds rich in organic matter. Elsewhere in the Pacific, middle Cretaceous beds deposited on bathymetric highs are known to be uncommonly rich in organic matter (C_o = 1-9%). Second, if deposits of the global anoxic event accumulated on Aleutia, it is likely that large amounts of organic matter were conveyed to the now-abandoned Mesozoic subduction zone at the base of the Alaskan-Siberian margin Pelagic source beds for hydrocarbons may therefore be stored within fossil subduction complexes buried beneath the present continental rise prism.

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The potential occurrence of middle Cretaceous source beds beneath a steadily thickening pile of Cenozoic basin-plain and rise-prism deposits can be viewed as increasing the chances that deep-water reservoirs in the Aleutian basin have been charged by migrating hydrocarbons.

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