Hauterivian–Barremian marine molluscan fauna from the Tetori Group in Japan and late Mesozoic marine transgressions in East Asia

There are a few marine intercalations in the upper Mesozoic nonmarine deposits in the eastern part of the Asian continent, including the Tetori area, Japan, and the eastern part of the Heilongjian Province, China. Therefore, it is possible to apply international marine stage names roughly for these nonmarine deposits. We can then discuss the changes of terrestrial environments in East Asia and their accompanying terrestrial and freshwater biotas. e, two marine transgressions have been recognized in the Tetori Group, Japan. One is of the stage from Callovian to Oxfordian, and the other is from Tithonian to Berriasian. Recently a new marine biota was discovered from the Inagoe Formation of the Tetori Group. Four species of ammonites and 13 species of bivalves from the biota are described herein. The presence of Psedothurmannia aff. baleare, Phyllopachyceras infundibulum, and Acrioceras (Paraspinoceras) sp. suggests that the Inagoe Formation can be assigned to Hauterivian to Barremian. Those data indicate that the third marine transgression is represented in the Tetori Group. eastern part of the Heilongjian Province, China, two marine transgressions, the first from late Oxfordian to Volgian (=Tithonian to early Berriasian) and the second from Barremian to Aptian, are recognized. Therefore, those marine transgressions in China correspond to those in the Tetori area, Japan. esence of common marine bivalve species and related ammonite species suggests that the eastern part of the Heilongjiang Province of China and the Tetori area of Japan occupied the same faunal province during Hauterivian to Barremian time. These faunal compositions are different from those of the areas in the southwest of Japan influenced by currents from low latitudes. This supports the idea that a peninsula of land was present between both the Tetori area and areas in southwest of Japan. Thus, both areas of the eastern part of the Heilongjian Province of China and the Tetori area of Japan, were influenced by current from the high latitude.