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

1.对大原北部地区下、中叶佐群的菊石和接种胺生物地层学进行了修正，初步建立了稳定的碳同位素地层学。在该地区重建OAE1的四个亚流是很有可能的。中川地区下、中野佐群的菊石、接种胺和放射虫生物地层学基本建立，生物地层控制性得到很大改善。随着生物地球化学特征的变化，稳定碳同位素地层学基本建立。因此，很明显OAE 1是在这个地区产生的。在亚组的时间分辨率上完成了日本白垩纪菊石属种水平的数据库。阐明了日本白垩纪菊石的多样性变化强烈受控于OAEs的出现。很明显，在晚白垩世，菊石多样性逐渐减少，从大约700种减少到690种，K/T的影响非常小。

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.