Paleoceanography of the northwestern Pacific during the Albian

Abstract

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.