Calcareous Nannofossils from the Nankai Trough and Japan Trench, Deep Sea Drilling Project Leg 87

Abstract

Drilling at three DSDP drill sites on the western margin of the Pacific Ocean off the coast of Japan yielded thick sequences of hemipelagic muds and clays generally depleted of calcareous nannofossils. Operations at Sites 582 and 583 recovered dominantly Quaternary sediments. The Pliocene/Pleistocene boundary was reached near the bottom of Hole 582B. At both sites, preserved coccolith populations contained generally few to common nannoliths. The effects of reworking were evident throughout most sections at these two sites. Drilling at Site 584 in the Japan Trench recovered Holocene to Miocene sediments. Populations of nannofossils from this site were generally more depleted than those from the two Nankai Trough sites. Reworking within these sections appears to be much less severe than in samples from the more southern sites.

Calcareous Nannofossil Biostratigraphy of the Nankai Trough

“…The low diversity of the nannofossil assemblages described from previous DSDPlegs from the Nankai Trough area (Ellis, 1975;Lang, 1986) is also revealed in samples from Leg 131. The preservation of nannofossils in Site 808 sediments (approx.…”

“…Site 583 was drilled at the toe of the accretionary prism . The oldest sediments at Site 583 are early Pleistocene {Gephyrocapsa oceanica Zone NN20; Lang, 1986).…”