Viewing the tectonic evolution of the Kamchatka-Aleutian (KAT) connection with an Alaska crustal extrusion perspective

Abstract

The Kamchatka and Aleutian (KAT) arc-trench systems meet orthogonally at Cape Kamchatka Peninsula. The KAT connection is the intersection of the NE-striking Kamchatka subduction zone and the NW-striking, transform setting of the western, Komandorsky sector of the Aleutian Ridge. Deciphering the origin and evolution of the KAT connection is challenging because of the paucity of constraining information about the age and latitude of formation of major crustal blocks of the deep water Bering Sea Basin. It is proposed that in the late early Eocene (∼50 Ma) the combined tectonic machinery of subduction zone obstruction and continental margin extrusion created the tectonic and rock architecture of the Aleutian-Bering Sea region. Accretion of the Olyutorsky arc to the north Kamchatka-Koryak subduction zone forced the offshore formation of the Aleutian subduction zone (SZ), added a sector of Pacific crust-Aleutia-to the North America plate, and established the KAT connection. Subsequently, but also in the middle Eocene, extrusion of Alaska crust southwestward across the Beringian margin connecting Alaska and NE Russia buckled Aleutia and forced the offshore formation of the Shirshov and Bowers SZs. Extrusion was driven by northward oblique underthrusting beneath British Columbia and SE Alaska. In the early Tertiary the Aleutian and Kamchatka SZs, linked at the KAT connection, thus consumed northwest moving crust of the Pacific Basin and within the Bering Sea the Beringian, Shirshov, and Bowers SZs accommodated SW extruding Alaska and captured Aleutia crust. Since the early Miocene extrusion space has been provided by the Aleutian SZ. Arc-arc collisions at the KAT connection have been guided by the right-lateral Bering-Kresta shear zone, which lies at the Bering Sea base of the Komandorsky section and terminates at Cape Kamchatka Peninsula. In the past the tectonic connection with Kamchatka may have been farther to the north.