Late Quaternary deglaciation in the Arctic Ocean: evidences from microfossils

Integrated micropaleontological and sedimentological analyses on calcareous nannofossils, diatoms, planktonic and benthonic foraminifera and clay mineral assemblages have been performed on three sediment cores (Tab. 1), collected during the EGLACOM and CORIBAR projects from the Storfjorden- Kveithola depositional system (NW Barents Sea, Fig. 1). The recovered cores contain a thick sedimentary sequence that includes well preserved Holocene interglacial sediments. The lithological sequence and the magnetic susceptibility are consistent between the EGLACOM and CORIBAR cores, allowing the construction of a preliminary age model. The upper part of the CORIBAR core was directly related to the Holocene sequence contained in core EG-03, whereas the lower part was correlated to the post LGM sequence contained in core EG-02. We specifically report on the results from the Holocene interval that is characterized by a clear reprise of the North Atlantic Current (NAC) strength. 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 presence of nannofossils in the sediments is a clear indication of open-water/seasonal sea ice conditions as the nannofossils, unlike some diatom species, were photosynthetic algae that can not live under permanent sea-ice coverage. The nannofossil assemblages during the Holocene, are dominated by Emiliania huxleyi specimens smaller than 4 μm, confirming the deglaciation trend. 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 were associated to the Holocene Thermal Maximum. Minor climatic fluctuations with inversed trends within the Holocene are well depicted by the microfossils assemblages and distribution of the smectite clay mineral.