Carbon isotope data of terrestrial organic matter (δ13CTOM) obtained in Hokkaido, northern Japan, from the marine Cretaceous Yezo Group along the northwestern Pacific margin elucidated a detailed chemostratigraphy for the Turonian Stage in this region of East Asia. Chemostratigraphic intra-basin correlation reveals three positive δ13CTOM events in the Middle–Upper Turonian of the Yezo Group. δ13CTOM fluctuations in these events show similar patterns in the Yezo Group, indicating that terrestrial organic matter is mixed sufficiently before deposition in the Yezo Basin. These δ13CTOM events are correlated with previously documented δ13Ccarbonate events in Europe (the Lulworth–Round Down, Glynde–Pewsey, and Late Turonian Events) based on global biostratigraphy. Our chemostratigraphic correlations strengthen the use of these δ13C events for global correlation of the Turonian marine successions. In addition, global correlation of Turonian marine and terrestrial δ13C events identifies changes in isotopic difference between δ13CTOM and δ13Ccarbonate (ΔTOM–carbonate), which are interpreted to reflect changes in atmospheric pCO2 levels, and climate-driven stresses of humidity and soil processes. In earlier stages of Turonian, ΔTOM–carbonate values are increased. Elevated atmospheric pCO2, and increased humidity and soil processes in enhanced greenhouse conditions during mid-Turonian, are interpreted to enlarge ΔTOM–carbonate values. In later stages of Turonian, ΔTOM–carbonate values are at a constant level, and the lowering of atmospheric pCO2 or decrease of climate stress related to the diverse paleoclimatic cooling is interpreted to have restored the ocean-atmosphere δ13C trends.
- Received 12 June 2012.
- Revision received 3 February 2013.
- Accepted 4 February 2013.
- © 2013 Geological Society of America