Deposition of Organic Matter in the Norwegian-Greenland Sea during the Past 2.7 Million Years

Variations in the amount and composition of sedimentary organic matter in glacial and interglacial deposits of the last 2.7 myr correlate with late Cenozoic climatic and oceanographic changes in the Norwegian-Greenland Sea. These variations are predominantly caused by the changing supply of terrestrial and reworked organic matter. The highest amounts of terrestrial organic particles (macerals) and of reworked coal clasts in glacial and early deglacial diamictons are closely related to glacial erosion of Mesozoic strata that crop out along the Scandinavian Shelf. The first occurrence of coal clasts at 2.53 myr demonstrates an initial advance of continental ice margins to these source areas. The establishment of anoxic conditions at the sea floor during diamicton deposition probably reflects an increased vertical flux of labile organic matter due to lithogenic adsorbtion followed by an almost complete mineralization at the water/sediment interface. The content of marine organic matter was continuously low over the past 2.7 myr except for past interglacial highstands (i.e., isotopic event 5.5.1), suggesting persistent diagenetic degradation of the labile organic fraction. The marine organic matter exclusively consists of residual dinoflagellate cysts and fragments of them.