The deep ocean conditions and circulation during the Cretaceous have been characterized mainly by the sediments from the Tethys Sea and the proto-Atlantic Ocean, because sedimentological data from the Pacific basin from that period have been quite limited. Here we present new geochemical measurements from sediments that we collected from two sites in Hokkaido, Japan, that were presumably deposited in the northwest Pacific during the Albian (∼ 112 Ma). The low organic carbon and carbonate contents, combined with other measurements, from our study suggest that the mid-depth northwest Pacific during the time of deposition was corrosive to sedimentary carbonate but oxic. We also use a simple box model of the ocean biogeochemistry to investigate the conditions of carbonate preservation and suggest that the northwest Pacific hydrography was quite distinct from the Tethys Sea and the proto-Atlantic Ocean.
Bibliographical noteFunding Information:
The authors wish to thank K. Minoura of (Tohoku University) and Lallan P. Gupta (CDEX) for helpful suggestions, M. Nohara (AIST) and K. Minoshima (AIST) for their technical assistance in geochemical analysis, and F. Surlyk and anonymous reviewers for their reviews. Special thanks are also due to K. Kobayashi (Mikasa City), his family, Y. Hikida, T. Matsuda (Nakagawa Museum of Natural History), and colleagues for their kind supports during the fieldwork. Additional support was provided by the Nippon Foundation Hadal Environmental Science/Education Program (HADEEP). This study was supported by the following research programs: “GCMAPS Program (Global carbon cycle and related mapping based on satellite imagery)”, funded by the Ministry of Education, Culture, Sports, Science and Technology of Japan, and the grant-in-ad for scientific research of 17253006 and 16340161 funded by the Japan society for the promotion of science.
- Box modeling
- Northwestern Pacific