Integrated sedimentology and micropaleontology for the study of the deglaciation post LGM in the south-western Svalbard slope (Arctic Ocean)

The north-western continental margin of the Barents Sea represents the only gateway for deep-water masses moving between the North Atlantic and the Arctic Oceans. On this respect, the western Svalbard margin, located on the eastern side of the Fram Strait, represents a key area to study the paleoceanographic variation of the West and East Spitsbergen currents. Integrated sedimentological and micropaleontological analyses on calcareous nannofossils, diatoms, planktonic and benthonic foraminifera and clay mineral assemblages have been performed on three sediment cores, collected during the EGLACOM and CORIBAR projects from the Storfjorden-Kveithola depositional system (NW Barents Sea), to reconstruct the deep-water paleoceanographic evolution after the Last Glacial Maximum. The lithological sequence and the magnetic susceptibility are consistent between the EGLACOM and CORIBAR cores. The recovered cores contain an expanded sedimentary sequence that includes continuous Holocene interglacial sediments. The microfossils are scarce in the lithological units that represent the deglaciation after LGM and became abundant in the Holocene sequences that record a clear upswing of the North Atlantic Current (NAC) strength. Nevertheless, the benthic assemblage is indicative of non-permanently ice-covered conditions since about 16 cal ka BP. The planktonic microfossil patterns of distribution are coherent with the trend of smectite content in the clay mineral assemblage that is mainly transported by the NAC, therefore high contents are associated to a vigorous current (Junttila et al., 2010). The nannofossil assemblages during the Holocene, are dominated by Emiliania huxleyi (< 4 µm), confirming the climatic amelioration. The diatom assemblages are dominated by Chaetoceros resting spores, related to stratified waters in association with ice melting at the beginning of Holocene. The presence of the diatom Coscinodiscus spp. and a more diversified planktonic foraminiferal assemblage, with Neogloboquadrina pachyderma (s), N. incompta and Globigerina bulloides, indicating subpolar conditions, confirm the onset of warm environmental period that was associated to the Holocene Thermal Maximum. The benthic foraminiferal assemblage contains Cassidulina reniforme, C. teretis, Islandiella helenae/norcrossi, Melonis barleeanum and Cibicidoides wuellerstorfi. The significant occurrence of small taxa, such as Stetsonia horvati, during the medium-late Holocene suggests a condition of low productivity and limited flux of organic matter to the sea floor. The abundance of agglutinated species, corresponding to high percentage of calcareous benthic foraminifera fragmentation, indicate the presence of aggressive bottom waters and, could suggest the influence of brines, cold, salty and dense waters, coming from the shelf area.