Hakobuchi Formation

The Hakobuchi Formation is a geological formation in Hokkaido, Japan. It is the uppermost unit of the Yezo Group, being early Maastrichtian in age. It consists of bioturbatedglauconiticsandstones, siltstones and conglomerates with coalymudstone and minor tuffite. It was deposited in a continental shelf setting. It is noted for its fossil content with the invertebrates mainly consisting of bivalves and ammonites. With vertebrates including the mosasaursMosasaurus hobetsuensis and Phosphorosaurus ponpetelegans. As well the sea turtle Mesodermochelys and the hadrosaurid dinosaur Kamuysaurus.