Late Cenozoic sedimentary environments in the Amundsen Basin, Arctic Ocean

Analyses of sediment cores recovered on the Arctic ’91 cruise with RV Polarstern to the Amundsen Basin and Lomonosov Ridge identify four main sedimentary facies and associated depositional sedimentary processes. These include: (1) homogenous mud facies interpreted as hemipelagic deposits, most abundant in the central parts of the Amundsen Basin; (2) fining upward cycle facies interpreted as fine-grained distal turbidite deposits, present in all Amundsen Basin cores, but most abundant laterally in the basin; (3) massive diamicton facies, found in the North Pole core; and (4) laminated diamicton facies, abundant in the upper parts of Lomonosov Ridge cores. Both diamictons are heavily influenced by ice-rafted debris, and the massive diamicton may result from redeposition of laminated diamicton downslope from the Lomonosov Ridge. The Lomonosov Ridge core exhibits a sedimentation rate of 29 mm/ka, while the sedimentation rates of turbidite rich sediments of the Amundsen Basin may be up to 10 times as high. Clay minerals show that the eastern Kara Sea and the Laptev Sea is the source area for most of the sediments, while some clay mineral zones may have their source in northern Greenland or the Barents Sea shelf.