How is black shale formation in the Early Eocene Arctic Ocean influenced by export of terrestrial organic matter? Details from an organic petrological approach on marine sediments from IODP Hole 302 (Lomonosov Ridge)

• Main Authors: Boucsein, B., Knies, J., Stein, Rüdiger
• Format: Conference Object
• Language: unknown
• Published: 2008
• Subjects: Arctic; Arctic Ocean; Lomonosov Ridge
• Online Access: https://epic.awi.de/id/eprint/18641/; https://hdl.handle.net/10013/epic.30338

In 2004 the IODP Expedition 302 (ACEX) recovered a 430m thick sequence of upper Cretaceous to Quaternary sediments on the Lomonosov Ridge in the central Arctic Ocean (Backman et al. 2006). For the first time insights in the environmental Pre-Pleistocene history of the Arctic Ocean are possible (see e.g. Brinkhuis et al. 2006, Moran et al. 2006). Our results of the organic geochemical basis parameters (total organic carbon (TOC), stable carbon isotopes (δ13C), total organic carbon/total nitrogen (C/N) ratios, total organic carbon/total sulphur (C/S) ratios, Hydrogen indices) and first maceral data on the entire ca. 200m thick Paleogene organic carbon (OC) rich section have been published recently (Stein et al. 2006).Here, we will focus on the black shales formed during the global δ13C-events Paleocene/Eocene Thermal Maximum (PETM) and Elmo. New detailed organic petrographical data (maceral analysis) are compared with the results of organic geochemistry (basis parameter, organic and inorganic nitrogen fraction). Such combined petrographical and organic geochemical approaches were established during the last decades, especially to solve questions concerning the paleoenvironmental conditions of recent and ancient marine deposits.During the Paleocene/Eocene the Early Arctic Ocean was an enclosed basin influenced by warm surface-water temperatures as indicated by TEX86 data (Sluijs et al. 2006). Data on e.g. radiolarians, terrestrial palynomorphs (Backman et al. 2006) and maceral data (Boucsein and Stein, subm.) give evidence for river run-off causing low-surface salinity. Therefore, fluvial nutrient supply may have induced primary productivity as it is also suggested from the abundances of marine diatoms and diatom resting spores (Backman et al. 2006). The isolated position of the Arctic Ocean during that time combined with freshwater discharge support the idea of OC accumulation in an anoxic basin with a stratified water column. We found abundances of finely dispersed and small sized pyrite framboids (<5µm, ...