Palaeontologic and isotopic study on the environmental changes during the Late Mesozoic

点击翻译按钮获取中文摘要

1. Ammonoid and inoceramid biostratigraphy for the Lower and the Middle Yezo Group in the North Oyubari area was revised, and the stable carbon isotope stratigraphy was nearly estblished. It is highly possible to reconstruct four subevents of OAE 1 for this area.2. Ammonoid, inoceramid and radiolarian biostratigraphy for the Lower and the Middle Yezo Group in Nakagawa area was nearly established, and the biostratigraphic control was much improved by this work.3. The stable carbon isotope stratigraphy was nearly established for the succession, together with the change of biogeochemical features. Thus, it became clear that OAE 1 arose in this area.4. Database of Cretaceous ammonoids in Japan at the level of species was completed in the time resolution of subage.5. It was elucidated that the diversity change of the Japanese Cretaceous ammonoids was strongly controlled by the arise of OAEs.6. It became clear that ammonoid diversity gradually decreased during the Late Cretaceous from about 700 species to 690 species, and the influence the K/T impact is extremely small.