Deposition of organic carbon in Arctic Ocean sediments: terrigenous supply vs marine productivity

During the ARCTIC ′91-Expedition with RV “Polarstern”, several Kastenlot-cores were recovered along a profile crossing the eastern part of the Arctic Ocean. In this paper we present results of detailed sedimentological and organic geochemical investigations on three of these cores, which have yielded a wide range of data for the interpretation of the flux and type of organic matter. In general, the high organic carbon content of the sediments is derived from a high input of terrigenous organic matter. The variation in content and composition of the organic carbon in the sediments of Core PS2174-5 reflect glacial/interglacial changes. Interglacial Stages 7 and 5e reveal a low organic carbon content (< 0.5%) and, as indicated by high hydrogen indices, low C/N ratios, higher content of n-alkanes (C17 and C19), and a high opal content, reflect higher marine productivity. During the glacial stages (Stages 6, upper 5, and 4), organic carbon values are significantly higher (0.7–1.3%). Low hydrogen indices, high C/N ratios, low short chain n-alkanes, and low opal contents provide evidence for a higher input of terrigenous organic matter and reduced marine productivity. Changes in the content and composition of the organic carbon are believed to vary with the fluctuations in sea-level and sea-ice coverage.