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Kristin Johanne Grasmo, University of Bergen (Norway)
Haflidi Haflidason, University of Bergen (Norway)
Hans Petter Sejrup, University of Bergen (Norway)
Christine Zuhlsdorff, University of Bergen (Norway)
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A detailed record of the Marine Isotope Stage 7 (MIS 7) has been studied in core MD99-2288 from the southern Vøring Plateau, Norwegian Sea. The core was raised from a water depth of 1262 m and is today influenced by the Norwegian Sea Arctic Intermediate Water (NSAIW) and Atlantic Water masses (Norwegian Atlantic Current). Approximately 150 samples were analysed with emphasis on the benthic and planktonic foraminiferal fauna, stable oxygen and carbon isotopes (Neoglobigerina pachyderma s., Cassidulina neoteretis), sediment texture and MSCL-analyses. The MIS 7 record in the Norwegian Sea showed the same paleocenaographic general pattern as found in records studied further south; divided into three warm and two cold periods.
The results show, however, that MIS 7 in the Norwegian Sea was a in a general much colder interglacial than found in MIS 5e and the Holocene, with a summer sea surface temperature of around 4°C. This indicates a stronger influence of the East Greenland Current and Arctic water masses and a more southward location of the Arctic Front compared to today. During the colder substage periods the Arctic Front was probably situated close to the core site, indicating surface sea conditions similar to glacial periods. The MIS 7 is characterised by one very cold stadial-like period, MIS 7.4, characterized by heavy benthic and planktonic 18O values. At the end of this cold period a spike of light planktonic 18O values are explored concomitant with a sequence of faintly laminated sediments (sed. rate appr. 11 cm/ka). The sediments are interpreted to be plumites deposited by melt water plumes during a strong melting phase of the Fennoscandian Ice Sheet. The benthic and the planktonic foraminiferal fauna support also formation of a freshwater lid and intrusion of Atlantic Intermediate Water masses beneath this lid. During MIS 7 there is little variation in the planktonic foraminiferal fauna as the dominance of N. pachyderma s. is around 95 %, whilst the benthic fauna shows a rather high diversity and greater variation. The benthic fauna for MIS 7 is therefore recording in some detail the paleoenvironmental conditions in the intermediate water masses for this period in the study area.
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