Trace-element geochemistry of sediments and sulfur isotope geochemistry of framboidal pyrite from Site 795, Leg 127, Japan Sea

Abstract

The changes in redox condition of the bottom water of the sea are estimated from vertical variations of redox sensitive elements (TOC, TS, Mn, Sb, U, and As). These data were compared to those from a piston core collected near Site 795. The estimated changes in the redox condition are: a variation between less oxic and less euxinic in Units 5, 4B, 4A, and 3 (ca. 13-15 to 6-7 Ma); oxic but less so than that of the present Japan Sea with diagenetic sulfate reduction under very high biological productivity in Unit 2 (ca. 6-7 to 2.4 Ma); and a drastic variation between oxic, similar to the present bottom water, and euxinic, similar to that during the last glacial period in the sea, in Units 1B (ca. 2.4-1.2 Ma) and 1A (ca. 1.2 Ma to the present). -from Authors