Benthic foraminifers and paleobathymetry of the Japan Trench area, Leg 57, Deep Sea Drilling Project.

Abstract

During the Late Cretaceous a deep bathyal environment persisted, characterized by deposition of fine-grained turbidites. Sometime during the early Paleogene, uplift occurred, followed by erosion and deposition of a conglomerate which presumably derived from a nearby volcanic source. A shallow marine sequence consisting of a massive sandstone marked by shallow-water benthic foraminifers, gastropods, and pelecypods was deposited in the late Oligocene. During the early Miocene a fine-grained turbidite-claystone was deposited on a subsiding slope. Subsidence continued throughout the Miocene and reached lower bathyal depths by the late Miocene, accompanied by deposition of a thick hemipelagic sequence. A gradual shoaling is indicated by benthic foraminiferal assemblages of the late Pliocene to Pleistocene.-from Author