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SEDIMENTATION IN TEMPELFJORDEN, SPITSBERGEN, HIGH ARCTIC – PRELIMINARY RESULTS
FORWICK, MATTHIAS University of Tromsø, Norway.
Vorren, Tore O. University of Tromsø, Norway.
The fjord Tempelfjorden is the easternmost tributary to Isfjorden, which is the largest fjord on Spitsbergen, Svalbard. Two major sources contribute sediments to Tempelfjorden: the glaciers Tunabreen and Von Postbreen at the fjord head, as well as the river Sassenelva close to the mouth of the fjord. Whereas the sediments released from the glaciers are of reddish colour, the suspension from Sassenelva is brown. Since Sassenelva is frozen during winter (from September/October to June) the brown sediments can be used as markers for summer deposition. Plassen et al. (in press.) analysed one sediment core from the same position and they suggest that the stratified deposits at this location are glacimarine warves.
During a scientific cruise in 2003, the suspensions off Sassenelva and the glaciers were sampled. X-Ray Diffraction (XRD) analyses revealed different mineralogical compositions for the two suspensions. The suspension from Sassenelva comprises mostly quartz, but also mica, gypsum and clay minerals. However, the mineralogical composition of the suspension from the glaciers is dominated by dolomite and calcite, but it also contains quartz, mica and clay minerals.
A series of gravity cores along several transects across the fjord has been retrieved. They indicate that the impacts of the two sources on the sedimentation pattern change laterally within the fjord. Whereas sediments in the outer part of the fjords almost exclusively are delivered from Sassenelva, deposition in the inner part of Tempelfjorden is dominated by sediment input from the glaciers. However, in central parts of Tempelfjorden, the impact of both sources is almost equal. The gravity core JM03-048-GC from central parts of Tempelfjorden comprises intercalated reddish and brownish sediments. High-resolution (2-mm steps) geochemical analysis of core JM03-048-GC, using a X-Ray Fluorescence (XRF) Core Scanner shows marked elemental differences between the different coloured strata: the more brownish the strata, the higher the Fe- content, and the more reddish the strata, the higher the Ca-content. Measurements of the magnetic susceptibility show a similar pattern: the browner the sediment, the higher the magnetic susceptibility.
Throughout the sediment column, the thickness of reddish and brownish strata varies, indicating varying impact of the two sediment sources on accumulation at the location over time. Since water circulation in Tempelfjorden is relatively slow and surface water movement is predominantly wind-driven, the varying thicknesses might be an indicator for prevailing wind directions in central Spitsbergen during the summer months.
Plassen, L., Vorren, T.O. & Forwick, M., in press. Integrated acoustic and coring investigations of glacigenic deposits in Spitsbergen fjords. Polar Research 23(1), xxx-xxx.
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