Abstract: The Cretaceous sequence in Hokkaido might be classified two major groups by the orogenic cycles. The agency of the first orogenic cycle origenated in Okhotsk Sea and shift the basin in the direction of south-west. It is in the cycle that the Lower Cretaceous (Neocomian-Cenomanian) formations were deposited.
The second that was caused by the elevation of the Honshil arc moved the basin in the direction of east, from the western Honshu are to the eastern Pacific Ocean. In this cycle, the Upper Cretaceous (Turonian-Maestrichtian) formation were deposited.
Each of the major cycles has two minor cycles. The former break of them is between the Neocomian and Aptian, and latter between the Campanian and Maestrichtian.
Corresponding with them, each several breaks of fauna could be recognized. Particularly, the faunal break between the Cenomanian and Turonian is most dominant.
The isopach maps of each formation are shown, Figs. 1-4. The depositional cross section from east to west is shown, Fig. 5.