Middle Miocene to Pliocene sedimentary basin analysis of vertical movements in Hokkaido, Japan

  • Tsumoru Sagayama Department of Marine Geosciences, Geological Survey of Hokkaido, Chikko 3-1, Otaru, 047-0008 Japan.
Keywords: Neogene, basin analysis, vertical movement, Hokkaido.


Neogene Tertiary sequences are widely represented in the Japanese Islands. Sediments of Neogene Tertiary are particularly well represented in Hokkaido, the northernmost part of Japanese Islands. Detailed Neogene Tertiary stratigraphy provides regional context for correlation with Tertiary in the Honshu, the main land of Japan, and the Sakhalin and Kamtschatka regions of Russia. Paleo-sea level was reconstructed, based on four sedimentary facies, for 27 of 31 basins studied. Unconformities indicate exposure of land surface during regression, whereas the facies of conglomerate, sandstone, siltstone, and mudstone represent sedimentation under changing sea levels during transgression. 31 basins studied represent nine types of vertical movements. Subsidence rates for the late Miocene, early Pliocene and late early Pliocene show a tendency to become faster as geologic ages become younger.