Up-current geomorphic events and local tectonics as primary controls on sediment transport by the West Spitsbergen Current and sedimentation in the Fram Strait since ca. 3 Ma

Abstract

International Ocean Discovery Program Expedition 403 recovered the longest sediment cores from the Svyatogor Ridge (SR) and Vestnesa Ridge (VR) to date, enabling hypothesis testing of competing influences on sediment drift evolution in the Fram Strait, with implications for ocean circulation. We found that regional geomorphic events and local tectonics exerted first-order controls on Pliocene–Pleistocene accumulation rates in eastern Fram active half grabens on the western flank of the Strait sediment drift through modulation of sediment supply to the West Spitsbergen Current (WSC) and depositional accommodation space. Expedition 403 drill cores show significant reductions in sediment deposition ca. 2 Ma and ca. 1 Ma. Linear sedimentation rates (LSRs) were more than twice as high at SR compared to VR before ca. 2 Ma, suggesting SR was a more significant depocenter than previously thought. This disparity appears to be linked to tectonically influenced paleobathymetry associated with extensional faulting. A major decrease in LSRs ca. 2 Ma coincided with the Barents Shelf changing from subaerial to marine, likely reducing erosion and sediment supply to the WSC. A further decrease in LSRs occurred ca. 1 Ma, during the mid-Pleistocene transition. This change aligns with increased Barents Seaway excavation, suggesting that reduced sediment input to the northern margins relates to a reorganization of ocean circulation. A weakened WSC no longer served as the only route for current flow and sediment transport from the North Atlantic to the Arctic Ocean, as the Barents Sea route was also viable when ice free.