抄録
Northern Honshu, Japan, is a classical example of a trench-arc-back arc basin system, and provides exceptional opportunities for better understanding plate subduction. In this paper, data from deep seismic profiles, petrology and petroleum geology are used to construct a geologic framework for the late Cenozoic development of the back arc area of central northern Honshu. At this time, two rift systems can be recognized in northern Honshu: the Yamato basin rift system along the eastern part of the sea of Japan and the northern Honshu rift system in the western part of northern Honshu island. The eastern part of the Yamato basin rift system is marked by half grabens bound by west-dipping Miocene normal faults, with the thickness of the crust decreasing toward the west due to early Miocene crustal stretching. The northern Honshu rift system is younger, forming in the middle Miocene, and produced the Akita-Yamagata sedimentary basin by a simple shear type of rifting. Basalts were erupted in conjunction with rifting. This produced a high thermal regime, and a shallow brittle/ductile detachment formed along the rift axis with associated thinning of the upper crust. Middle Miocene basin development was mainly controlled by normal faulting along the detachment. Based on our balanced geologic cross-section, the total amount of Miocene extension of the northern Honshu rift system is ca. 40km. Due to subsequent shortening since Pliocene, the low-angle detachment was reactivated as a thrust.
