Palaeontological and geochemical study of Late Cretaceous oceanic anoxic event

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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.