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

据初步报道，晚中生代白垩纪曾发生过三次大洋缺氧事件，分别为Albian期、Cenomanian/Turonian期界线和Coniacian-Santonian期。其中，Cenomanian/Turonian界线大洋缺氧事件研究最为深入，因为该事件所处的时代界线是IUGS白垩纪地层学小组委员会的连续研究对象，在北美和欧洲有许多有利的剖面，世界上也有许多容易获得的时代剖面。这个时代的生物地层分辨率在日本层序中也很高，因此事件的时间相对容易阐明。证实了大洋缺氧事件在朱蒂新心角石带下方和德文瓦氏角石带上方之间的时间内完成。因此，日本巨型化石生物地层学的高分辨率在不同的学科中得到了体现。研究了空知组和下冶佐组泥岩样品的总有机碳含量、烃类成熟度、生物标志化合物和稳定碳同位素分析。同时研究了菊石、双壳虫和放射虫的生物地层学特征，并对国际相关性进行了分辨率修正。这些工作的结果是确认的四次海洋缺氧事件之间的Aptian和Albian在Yezo弧前盆地的年龄。这是西北太平洋下白垩纪缺氧事件的第一个具体证据。

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.