Abstract

High-resolution profiles of organic carbon, δ13Corg, sulfur,δ34S, and some trace elements in cores from two silled basins, Kau Bay (Indonesia) and the Black Sea, allow division of the sedimentary record into three distinct units, representing a Pleistocene fresh-water-brackish water facies (unit 3), a Holocene transitional facies (unit 2), and a modern fully marine facies (unit 1). The geochemical characteristics of these units are strikingly similar for both basins. The sediments from unit 3 are characterized by the predominance of terrestrial organic matter, Mo and U concentrations at crustal abundance, and positive δ34S values. The transitional sediments (unit 2) are strongly enriched in marine organic matter and Mo, V, and U and have intermediate δ34S values. Sediments from the modern marine facies (unit 1) are moderately organic-carbon rich and slightly enriched in Mo and U and have negative δ34S values. The organic-carbon-rich sediments from unit 2 were formed by increased production during the transition from the Pleistocene isolated fresh-water-brackish water environment to the modern open-marine facies. This temporarily higher productivity was caused by displacement of nutrients from the deep water into the euphotic zone, owing to the gradual infilling by marine waters.

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