Sedimentary processes west off Svalbard during the initial warming after the Last Glacial Maximum (Bølling/Allerød)

• Main Author: Schiele, Kevin
• Format: Thesis
• Language: unknown
• Published: 2013
• Subjects: Arctic; Barents Sea; Norway; Svalbard; Yermak Plateau; Ice Sheet; Magnetic susceptibility; Northern Norway; Sea ice; Svalbard margin; Yermak plateau; Spitsbergen
• Online Access: https://epic.awi.de/id/eprint/33960/; https://hdl.handle.net/10013/epic.42305

Sedimentary processes along the Svalbard continental margin are strongly coupled with climate and oceanographic conditions. Sea ice and ice sheet dynamics have a major influence on the sedimentary record of the Arctic regions. The study aims to elucidate the processes that caused the deposition of a unique fine- grained sediment layer at the onset of the last deglacial basically along the western Svalbard margin and the western Yermak Plateau. Grain-size analyses of eleven sediment cores west and north off Svalbard and the Yermak Plateau reveal an exceptionally fine-grained sediment layer that was deposited within a relatively short period of ~300 years during the Bølling interstadial. The layer was found in sediment cores located below the West Spitsbergen Current that conveys Atlantic and mixed water masses northwards along the continental slope. As yet the sediment layer was found in 32 sediment cores (mostly published data) from ~72°N to ~82°N at water depths ranging from ~300 m (Kveithola) to 1880 m (Yermak slope) south, west and north of Svalbard and close to northern Norway. The studied fine-grained layer reveals a sortable-silt mean grain size of 11 to 19 μm. The fineness of this layer is basically the result of a coarse-silt subpopulation between ~36 and 63 μm that is absent in this layer but present throughout most of the cores. Very low magnetic susceptibility, a distinct decrease in Ca-ratios and slightly increased Ti-ratios are further key characteristics for the investigated layer (XRF analyses of four sediment cores). AMS age determinations of another four sediment cores show a doubled to tenfold increased sedimentation rate for the period of deposition of this layer. Proved by grain-size analysis the greatest thickness of the fine-grained layer appears in sediment cores from 1350 to 1550 m water depth and decreases in cores deeper than ~1600 m and cores shallower than ~1100 m water depth (except for Kveithola), respectively. Thus, the fine-grained material was transported northwards in a relatively narrow strip along the western Svalbard and Yermak slopes. The distribution and thickness of the investigated sediment layer can be linked to both, the rapid melting of the Svalbard and the Barents Sea ice sheets in response to the intense warming at the onset of the Bølling period. Since Kveithola trough is assumed to be fully deglaciated since 14.7 cal ka BP a sediment source in the adjacent Barents Sea as well as from local fjords of Spitsbergen is likely. A shift in the clay mineral composition for the deposition of the fine-grained layer supports this assumption.