Carbon isotope fluctuations of terrestrial organic matter for the Upper Cretaceous (Cenomanian–Santonian) in the Obira area of Hokkaido, Japan

• Published in: Geological Magazine
• Main Authors: URAMOTO, GO-ICHIRO, ABE, YOSHIHIRO, HIRANO, HIROMICHI
• Format: Article in Journal/Newspaper
• Language: English
• Published: Cambridge University Press (CUP) 2009
• Subjects: Geology; Methane hydrate
• Online Access: http://dx.doi.org/10.1017/s0016756809006487; https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0016756809006487

Abstract Stratigraphic fluctuations of carbon isotope values of terrestrial organic matter within the Upper Cretaceous (Cenomanian–Santonian) sequence in the Obira area of Hokkaido, Japan, record distinctive δ 13 C fluctuations for the Cenomanian–Turonian boundary, the Middle Turonian, the upper Turonian–lower Coniacian, and the Santonian. A biostratigraphic framework of the age-diagnostic taxa (ammonoids, bivalves and planktic foraminifers) indicates that these δ 13 C fluctuation events are comparable with those recorded in δ 13 C data of terrestrial organic matter in Japan and marine carbonates in Europe. These correlations reinforce the utility of these δ 13 C events in terms of global chemostratigraphy. In particular, the δ 13 C patterns within the overall positive interval of the Cenomanian–Turonian boundary event are highly conformable between marine and terrestrial records. The consistent nature of these different records of δ 13 C fluctuation patterns demonstrates that the terrestrial organic δ 13 C data mirror the global-scale δ 13 C patterns in the carbon reservoir of ocean–atmosphere–terrestrial biosphere during the Cenomanian–Turonian boundary event. In addition, global correlation of short-term marine and terrestrial organic δ 13 C fluctuations of the Upper Cretaceous sequence indicate that the magnitude of several terrestrial organic δ 13 C events appears more amplified than that of coeval marine carbonate δ 13 C events. This correlation is interpreted to mean that the effects of local CO 2 emission into the atmosphere by release of terrestrial methane hydrate or biomass burning of terrestrial vegetation in the hinterland of the NE Asian region have been superimposed on the global δ 13 C trend and resulted in the terrestrial organic δ 13 C records of the Yezo Group.