84 K. Wakita / Journal of Asian Earth Sciences 72 (2013) 75–87 plates in Paleogene time. The second stage occurred between 13 and 8 Ma, when the Chishima Arc collided as forearc sliver with the western part of Hokkaido. The oblique subduction of the Pacific plate against the Chishima Arc was the main cause of the uplift of the Hidaka Mountains in central Hokkaido. In this collision the two arcs merged.