Evaluation of Oceanic Anoxic Events in Lete Mesozoic from the Environment-Earth Scientific point of view.

点击翻译按钮获取中文摘要

It has been preliminarily reported that oceanic anoxic events had happened at three times, Albian age, Cenomanian/Turonian age boundary and Coniacian-Santonian ages in Cretaceous of Late Mesozoic. Amoung these, the Cenomanian/Turonian boundary oceanic anoxic event has intensively studied, because the event situates in the age boundary which is the continuous target for the Subcommission of the Cretaceous stratigraphy of IUGS,there are many favorable sections in North America and Europe and there are many sections of the ages easily accessible for scientists in the world. Biostratigraphic resolution of this age is also high in the Japanese sequence, and therefore the timing of the event was comparatively easily elucidated. I confirmed the oceanic anoxic event finished in the time between Neocardioceras juddi zone below and Watinoceras devonense zone above. Thus, the high resolution of the Japanese mega-fossil biostratigraphy is demonstrated in the different discipline.The Albian oceanic anoxic event has been in chaos in recognition from the global point of view. I studied the total organic carbon contents, maturity of hydrocarbon, biomarker and stable carbon isotope analyzes of mudstone samples from the Sorachi and Lower Yezo Groups. I studied the ammonoid, inoceramid bivalvian and radiolarian biostragtigraphy at the same time for those groups and revised the resolution for the international correlation. These works resulted in the confirmation of four times of oceanic anoxic events in the ages between Aptian and Albian in the Yezo forearc basin. This is the first concrete evidence of the Lower Cretaceou anoxic events in the Northwestern Pacific.