Sixteen long sediment cores from the eastern Arctic Ocean, the Fram Strait and the Norwegian-Greenland Sea, documenting 200 000 years of sedimentation, were studied for their qualitative dropstone composition (>500 lain-fraction). In sediments from oxygen isotope stages 1-5, coal particles are usually subordinate components of the coarse fraction. In contrast to younger deposits, coal content in oxygen isotope stage 6 (186-128 ka) varies between 20% and 65% in the eastern Arctic Ocean and the Fram Strait and between 5% and 20% in the Norwegian Sea. Southward decreasing coal content and similarities in maturity and petrography of the coals indicate that the coal was transported by iceberg or sea ice rafting more than 1000 km to the south. It is suggested that during intervals of oxygen-isotope stage 6 drifting ice carried abundant coal fragments from the eastern Arctic Ocean southward through the Fram Strait into the eastern Norwegian Sea. Thus, surface circulation was then opposite to that of today.
Microscopic studies reveal a predominance of terrestrial organic matter in sediments of Site 808. Terrestrial vitrinite and inertinite are more abundant (73% to 100%) than marine organic matter (alginite, 0% to 27%), which increases from open oceanic deposits of the Shikoku Basin sediments to sediments of the outer trench wedge. The abundance of terrestrial organic matter is also reflected through carbon isotope values of -23‰ to -25.9‰. Mass accumulation rates of organic carbon are low in hemipelagic sediments of the Shikoku Basin (<0.2 g/cm 2 /k.y.) but increase significantly in sediments of the Nankai Trench (0.2 to 1.7 g/cm 2 /k.y.). Although the organic mass accumulation is high in sediments of the Nankai Trench, a comparison of sedimentation rates and total organic carbon suggests relative dilution of organic carbon through turbidite flows. Calculated marine paleoproductivity of organic carbon is low in sediments of the open ocean (Shikoku Basin) and increases closer to the shore (Nankai Trench). Thermal evolution of organic matter is obtained from vitrinite reflectance measurements. Two populations of vitrinites have been observed between 600 and 1234 mbsf. Reflectance values change with increasing depth and temperature in both groups of vitrinite (0.3% to 0.68% in group 1; 0.6% to 1% in group 2).
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.