SEDIMENT PROVENANCE IN LINNÉDALEN, WESTERN SPITSBERGEN, SVALBARD: A PROXY FOR LOCAL ENVIRONMENTAL CHANGE

In the Linné Valley of western Spitsbergen, the Linné glacier (Linnébreen) advanced and retreated throughout the Holocene. Sediment from Linnébreen is deposited into Lake Linné, located 5 km downvalley. Sediment provenance in Linnédalen is being studied as part of the NSF-funded Svalbard REU Project to calibrate lamination stratigraphy in Lake Linné. This valley lends itself to provenance studies because it contains three distinct rock types: carbonate rocks form the eastern mountains, a sandstone with coal seams forms the valley floor and low-grade metamorphic rocks (phyllites) form the western mountains.

The principal sediment source streams were identified on aerial photographs. Fine-grained sediment samples were collected from each streambed and source bedrock material was sampled. Lake sediments were taken every 200 m at 1-2 m water depth along the south shoreline where the main inlets enter the lake. The shallow 15 m east basin is fed by the main inlet carrying mainly glacially-derived sediment. The west basin of similar depth is fed primarily by a cirque stream that erodes only phyllites. The 35 m-deep north basin is not fed by any major inlets and is likely dominated by a mix of material carried by currents within the lake and derived from marine terraces on the east and west shores. Distal lake samples were recovered from the top 1-2 cm of short cores taken from these three basins.

Loss on ignition is a proxy for provenance: carbon content is high in lake sediments near the Linnébreen meltwater inlet (up to 6.5% weight lost at 550ºC). Carbon content decreases in the west basin as sediment input is dominated by the phyllite-eroding cirque stream. A previous study (Werner 1988) suggests that percent carbon in lake cores may be a proxy for glacier position in the valley. Glacial advances augment weathering of the sandstone/coal formation, causing more carbon deposition in the lake. The geochemical fingerprint of each sample is determined by XRF, with the goal of determining the percent contribution of each source area to the lake. Stream sample compositions are compared to the geochemical composition of layers within lake cores to extrapolate relative source contributions during the late Holocene. Changes in the relative contribution of each source area to the basins are attributed to environmental changes in the valley.