Pleistocene and Pliocene Foraminifera from the Sea of Japan, Leg 31, Deep Sea Drilling Project

Abstract

Pleistocene and Pliocene planktonic foraminiferal faunas found at Sites 299, 300, 301, and 302 in the Sea of Japan are dominated by Neogloboquadrina pachyderma and Globigerina bulloides s.l. including G. umbilicata. Minor accessory species include Globigerina quinqueloba, Globigerinita glutinata, G. uvula, and Globorotalia scitula. These species form a subarctic biofacies characteristic of upper Pliocene through Recent deposits in much of the sea. Only sparse faunas were recovered at Sites 300, 301, and 302, but quantitative analysis of a fair to good Pleistocene sequence at Site 299 in the Toyama Channel clearly records significant planktonic foraminiferal events correlative with the initiation of severe cooling at 900,000 yr B.P. and a significant interglacial warming about 500,000 yr B.P. Unusual paleooceanographic and geochemical environments have been created in this sea during glacial maxima and minima due to unusually shallow basin sills which, together with a relatively shallow calcium carbonate compensation depth (CCD), account for the virtual absence of calcareous foraminiferal assemblages from major portions of the sediments penetrated at Leg 31 sites in the Sea of Japan.

Late Cenozoic Changes in Flux Rates and Composition of Organic Carbon at Sites 798 and 799 (Sea of Japan)

“…The primary objective at Site 798 was to obtain a Miocene to Quaternary carbonate-rich sequence, which would provide a high-resolution paleontologic, isotopic, and sedimentologic record. Of major interest were reconstructions of (1) surface-and intermediate-water history including changes in surface-water productivity, dissolved oxygen content of deep-water masses, and the carbonate compensation depth (CCD), (2) changes from anoxic to oxic conditions known to have occurred during Miocene to Pliocene times (Ingle, 1975;Matoba, 1984), and (3) faunal and sedimentary responses to the tectonic evolution of the Japan Sea. The main objective at Site 799 was to reconstruct the depositional and tectonic history of the Kita-Yamato Trough as a typical environment for massive sulfide mineralization in a rifted continental-arc setting.…”

“…Thus, these sites are of major interest for studies of the mechanisms controlling the formation of organic-carbon-rich sediments in a marginal sea environment that occasionally was restricted from the normal open-ocean environment (cf. Ingle, 1975;Matoba, 1984).…”

Introduction

“…The eustatic lowstands may correspond to periods of anoxic deep water, manifested in geochemically distinct sediments in the Japan Sea. The oceanographic conditions prevalent during these lowstands contrast markedly with the unusually well-mixed and entirely oxic water mass of the Holocene (Hidaka, 1966;Miyake et al, 1968;Ujiie and Ichikawa, 1973;Ingle, 1975b;Matoba, 1984).…”

Late Cenozoic Changes in Flux Rates and Composition of Organic Carbon at Sites 798 and 799 (Sea of Japan)

“…Connection to the marginal seas to the north and south and to the western Pacific is restricted to the shallow Tsushima Strait (140 m water depth), Tsugaru Strait (130 m), Soya Strait (55 m), and Tartary Strait (15 m) (Fig. 2;Ingle, 1975;Matoba, 1984).…”