Geochemical characterization of the depositional environment of Paleocene and Eocene sediments of the Tertiary Central Basin of Svalbard

The Tertiary Central Basin (CTB) of Svalbard has been studied extensively in the past because it contains sediments from the Paleocene Eocene Thermal Maximum (PETM). Previous studies have found that a negative carbon isotopic extrusion (CIE) is presents without showing elevated concentration of organic carbon. In this study we extend the record of the CTB with a comprehensive inorganic and organic geochemical data set based on the sediments encountered in the research well BH 10-2008, comprising almost 1100 m of cored sediments. Major and trace elements analyses in combination with mineralogical, carbon isotopic, total organic carbon, and total sulphur measurements were used to reconstruct the depositional environments of the lower Paleocene Basilika Fm. up to the Eocene Aspelintoppen Fm. Several depositional environments have been suggested, which are consistent with the sedimentological interpretation of the respective well section. Back-calculation of the initial organic carbon concentration shows that bacterial sulphate reduction had a major impact on the persevered organic carbon inventory of the lower Basilika Fm. and of the Paleocene/Eocene transition section. Based on organic carbon loss introduced by bacterial decay, as well as measured isotopic composition, we estimate an initial isotopic composition of the evaluated sediments which helps to elucidate on the fate of labile organic matter and explains the unusually low organic carbon inventory of the Paleocene/Eocene transition sediments.