1991 Volume 34 Issue 34 Pages 159-161
The Neogene sedimentary basins in the central Hokkaido were formed by the tensional stress field of the early Middle Miocene. This tensional stress field was related to opening of the Japan Sea. The Middle Miocene submarine fan was formed in the basin of the Hidaka coastal area. The submarine-fan environment changed into the fan-delta environment in the late Middle Miocene. The three stage progradations of the fan deltas were controlled by the sea-level fluctuations.