Revised Diatom Biostratigraphy of DSDP Leg 19 Drill Cores and Dredged Samples from the Subarctic Pacific and Bering Sea

Abstract

Revising the Miocene through Pleistocene diatom biostratigraphy on the drill cores recovered in DSDP Leg 19 results in the dating of Neogene sequences especially for Sites 183 and 192 in the far North Pacific Ocean. Ages for the basal part of the lithologic unit A (opal-A), diatom ooze to diatomaceous mud, overlying the unit B (opal-CT), mudstone with no diatom, are older than 10 Ma at 210 mbsf in Site 183, about 9.5 Ma at 718 mbsf in Site 192, and about 4.6 Ma at 582 mbsf in Site 188, at 370 mbsf in Site 187, at 587 mbsf in Site 185 and at 599 mbsf in Site 184, and about 3.2 Ma at 521 mbsf in Site 191, at 618 mbsf in Site 190, at 541 mbsf in Site 189 and at 926 mbsf in Site 186. The diagenetic boundary between opal-A and opal-CT distinctively forms a diachronic plane in the subarctic Pacific. Fossil diatoms in the dredged samples from the Bering Sea indicate stratigraphically major increasing times of diatom mass accumulation rates in the North Pacific: 10-9 Ma, 7-6 Ma, and 3-2 Ma.