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The geologic, structural, and tectonic history of the Bering Sea area since Paleozoic time is best viewed in terms of major plate-tectonic interactions. The geotectonic style of disparate areas is apparently related to the nature of plate motion at the time of tectonic imprint. Three major structural belts that have existed since the Mesozoic can be traced from the Siberian sector across the Bering Sea and into Alaska. The northern belt, the Verkhoyansk-Chukotsk-Seward-Brooks, consists of miogeosynclinal sediments that were deposited beginning in earliest Mesozoic time. The middle belt, the Okhotsk-Chukotsk-Yukon-Koyukuk, consists of a Mesozoic magmatic arc and numerous allochthonous terranes, formed due to the convergence-subduction of a southern oceanic plate. The south rn belt, the Koryak-Anadyr-Peninsular, consists of terranes accreted during Cretaceous time and forms the southern limit of Mesozoic subduction.
During Late Cretaceous to early Tertiary time, these belts were oroclinally bent southward by an east-west compressional event, causing the subduction zone to shift to a more southerly location, thus forming the current Aleutian Island arc system, behind which the fragments of 2 Cretaceous oceanic plates were "trapped." These oceanic plate fragments may consist of an Early Cretaceous plate and a portion of the Kula plate(?), which carried a northward-migrating arc system. The hypothesized Early Cretaceous plate may have had a counterpart separated by a spreading ridge, both of which have been subducted beneath the Beringian margin.
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