Planktonic foraminiferal biostratigraphy and paleooceanography of the Japan Trench, Leg 57, Deep Sea Drilling Project.

Only sites 438, 439 and 440 yielded planktonic foraminiferal faunas providing a discontinuous late Cenozoic biostratigraphic record. The severe calcium carbonate dissolution in these sections is probably due to deposition beneath the CCD and to incursions of cold subarctic subsurface currents, low in salinity and high in oxygen, during periods of climatic cooling. Planktonic foraminiferal zonation and placement of zonal boundaries are difficult in the Leg 57 sites owing to dissolution intervals resulting in discontinuous ranges of species. However, a number of datum levels can be recognized and the faunal sequences correlated with similar sequences at Sites 310 and 296.-from AuthorSchool of Earth Sciences, Stanford Univesity, Stanford, California, U.S.A.