High resolution carbon isotope stratigraphy across the Cenomaian/Turonian boundary in the Tappu area, Hokkaido, Japan : correlation with world reference sections

High resolution carbon isotope stratigraphy encompassing the Cenomanian/Turonian boundary in the Tappu section, Hokkaido, Japan enables correlations to be made with Eastbourne and Pueblo world reference sections. The organic carbon in the sedimentary rocks of the Yezo Group is derived predominantly from terrestrial higher plants. The stratigraphic profiles of carbon isotope values in the Tappu section show remarkable variations. A brief and small peak in the lower part, an extended plateau-shaped peak with larger magnitude in the upper part, and a trough dividing the two peaks observed in the Tappu section are well known patterns for the isotope profiles of the reference sections. Close similarity of the patterns among these regions validates a precise correlation of the Japanese Cenomanian/Turonian boundary sequence with the international standard reference sections in North Atlantic and Western Interior Sea regions.