Evolution of collision-related basins in the eastern end of the Kurile Basin, Okhotsk Sea, Northwestern Pacific

摘要

A densely-meshed 9400 km long high-resolution seismic survey revealed the evolution of sedimentary basins in the southeastern rim of the Kurile Basin, offshore of eastern Hokkaido, NW Pacific. Hokkaido is situated in a collision zone not only of Okhotsk and Eurasian plates and also of the Kurile and NE Japan arcs. Offshore eastern Hokkaido is overlain by N-S-trending basins: Hamatonbetu-oki, Monbetu-oki, and Kitami-Yamato Sedimentary Basins (HOSB, MOSB and KYSB, respectively), and Abasiri-oki Trough (AOT), separated by zones of uplift. Depositional patterns of the HOSB and deformation of the adjacent Uplift Zone suggest the pull-apart origin of the basin related to dextral motions along the Central Sakhalin Fault, which extends to Hokkaido and binds the Okhotsk and Eurasian plates. The Uplift Zone adjacent to the MOSB suggests the initiation of subsidence in the Middle Miocene within a splay-fault basin with subsequent transformation into a 40 km wide graben in the Late Miocene and into a half graben in the Pliocene. The prelate Miocene unconformity is widespread. The KYSB and the AOT began as a concatenated basin in the south of MOSB in the Middle Miocene. In the Pliocene, the Kitami'Yamato Bank (KYB) was uplifted and divided the KYSB-AOT basin into KYSB and AOT. The KYB uplift was probably induced by the Kurile forearc sliver movement. The interpretation of structures suggests that the Kurile Basin may have opened in a N-S-direction, from dextral shearing along a collision zone in the Middle Miocene. In the Pliocene, the kinematics changed to a NE-SE spreading direction; because of southwestward migration of the Kurile Arc with respect to the NE Japan Arc. Com-pressional tectonics after the Pliocene may suggest the destruction of the Kurile Basin.