Sedimentary Derivatives of Green Sulphur Bacteria as a Molecular Proxy for the Assessment of Euxinic Conditions in the Photic Zone

Abstract

Organic matter burried in sediments contains a multitude of palaeoceanographic and palaeoclimatic signals. With the major developments in instrumental analytical chemistry in the last 20 years, the decoding of these signals has become possible and molecular fossils have become an important tool in the assessment of palaeoenvironments. For instance, the determination of the number of double bonds in sedimentary long-chain ketones derived from coccolithophorid algae is now a widely applied technique in palaeoceanography to determine past sea-surface temperatures (Brassell, 1993). In this paper we will demonstrate the use of molecular fossils derived from the carotenoid isorenieratene to assess photic zone euxinia in ancient depositional environments. As an example the redox state of the North Atlantic Ocean during the Cenomanian/Turonian (C/T) anoxic event will be evaluated.