抄録
The Aptian to Albian sediments of the Yezo Supergroup in the northern Oyubari area are well-laminated, being affected little by macrobioturbation. A positive peak of carbon isotope excursion, high organic carbon contents and high sulfur contents are detected in the middle Albian. The redox environmental indices, S2/S3, pristane/phytane and bisnorhopane/hopane ratios, show a reducing condition in this stratigraphic level. The good correlation of S2/S3 ratio vs. TOC indicates that the high organic carbon contents in this basin depend primarily on the reducing conditions. Therefore it is apparent that a reducing environment (i.e. anoxic to dysoxic environment) prevailed in this basin, and this regional event is correlated with the global OAE1c.
