Palaeontological and geochemical study of Late Cretaceous oceanic anoxic event

通过岩相、巨相、鱼相、硫含量、硫/有机碳比值等研究，明确了北海道大张和大比拉地区中野三群Cenomanian/Turonian界线层存在除西北太平洋外世界公认的Cenomanian/Turonian海洋缺氧事件。我们在法国格勒诺布尔和英国伦敦举行的一些国内年会和国际会议上报道了这一结果。首席研究员在非洲的北突尼斯和法国的普罗旺斯进行了考察和取样，并比较了北海道、北突尼斯和普罗旺斯之间的C/T边界的化学地层模式，证实了西北太平洋的塞诺曼尼亚/土伦尼亚海洋缺氧事件的存在。在第29届国际地质大会期间，首席研究员在北海道Oyubari和Mikasa的C/T边界暴露处进行了实地考察，讨论了研究层的OAE的可靠性。因此，我们成功地得到了这次事件的时间和世界范围的规模，我们现在正在研究的进一步课题是澄清与地球结构及其节奏有关的因果因素。

We clarified the existence of the so-called Cenomanian/Turonian oceanic anoxic event, which is world-widely recognized except Northwestern Pacific, in the Cenomanian/Turonian boundary bed of the Middle Yezo Group distributed in Oyubari and Obira, Hokkaido by the study of lithofacies, megabiofacies, ichnofacies, sulphur contents and sulphur/organic carbon ratio. We reported this result in some domestic annual meetings and international conferences which were held in Grenoble, France and London, UK. The head investigator visited and sampled in North Tunisia, Africa and Provance, France and compared chemostratigraphical patterns across the C/T boundary between Hokkaido, North Tunisia and Provance, confirming the existence of the Cenomanian/Turonian oceanic anoxic event in the Northwestern Pacific. The head investigator carried out the field trip in the occasion of the 29th International Geological Congress at the C/T boundary exposures in Oyubari and Mikasa, Hokkaido, discussing the reliability of OAE at the studied beds.Thus we succeeded in getting the timing and world-wide scale of the event, and further subject which we are now studying is to clarify the causal factor in relation to the earth structure and its rhythm.