Abstract

Strike-slip faults on the plate tectonic scale in arc settings significantly contribute to the movement of crustal blocks, crustal deformation, and orogeny associated with back-arc spreading, arc–arc collisions, and the subsequent evolution of arcs. The Tanakura Fault Zone, which was active during and after the opening of the Sea of Japan, is one of the main strike-slip faults in Japan. An understanding of the kinematic history of the Tanakura Fault Zone would provide insights into the tectonics of the opening of the Sea of Japan, the ensuing collision of the Honshu and Izu–Ogasawara (Bonin)–Mariana arcs, and the subsequent evolution of the Japanese island arc system. We investigated the activity of the Tanakura Fault Zone during the Miocene based on a field study along the Tanakura Western Marginal Fault in the Tanakura Fault Zone, analysis of deformed Miocene conglomerates, and provenance analysis of detrital zircon in Miocene strata. These results indicate that dextral faulting has occurred in the Tanakura Fault Zone since ~ 16 Ma. We obtained evidence of dextral movement along the Tanakura Western Marginal Fault from fault outcrops. This movement resulted in the formation of elongated granitic clasts in the deformed conglomerate through cataclastic deformation related to the faulting. In addition, cataclasite samples contain Paleozoic zircon grains, suggesting that some clasts were derived from the Paleozoic Hitachi Metamorphic Rocks. Paleozoic clasts were probably supplied as gravel to the area west of the southern Abukuma Mountains and were then transported several kilometers to the north-northwest by dextral movement on the Tanakura Eastern Marginal Fault in the Tanakura Fault Zone to reach their present location. Our findings suggest that dextral faulting of the Tanakura Fault Zone occurred due to NE–SW compression resulting from the collision between the Honshu and Izu–Ogasawara (Bonin)–Mariana arcs, which occurred as a result of the initiation of subduction of the Philippine Sea Plate, just after the opening of the Sea of Japan.