Extent of the Middle Cretaceous Orogen in Eastern Asia and the Geodynamic Causes of Its Transformation

An extensive Middle Cretaceous orogenic belt of East Asia, which occupies the Okhotsk–Koryak–Western Kamchatka territory, encompasses thrust-and-fold structures. It formed over an interval of 130–110 Ma as a result of perioceanic accretion–obduction processes involving marine allochthonous complexes up to the Barremian inclusive, which experienced large amplitude displacements. Under the remote impact of subsequent (end of the Cretaceous and Cenozoic) perioceanic tectonic events, the primary structures of the Middle Cretaceous belt underwent compression-related superimposed deformations and fragmentation of allochthons with negligible displacement amplitudes. This led to the formation within the belt of a mosaic pattern of alternating fragments of neo-autochthons and allochthons bounded by young thrusts and strike–slip faults, often suggested as independent heterochronous terranes.