INTERPRETING THE LAMINATION STRATIGRAPHY OF CORES RECOVERED FROM LAKE LINNÉ, SVALBARD NORWAY

A study of finely laminated sediment cores recovered from glacial Lake Linnč provide a detailed record of glacier and climactic conditions of approximately the past 2000 years in the high Arctic. Lake Linnč (40 m deep, 4.6 km long and 1.3 km wide) is located on the west coast of Svalbard Norway at 78°N latitude, 13°E longitude. Previous work shows that the Linnč glacier, located 6 km up-valley, experienced its last maximum around four thousand years BP and has been retreating since, depositing a well-preserved record in Lake Linnč.

In 2004-2005, four short cores (0.5 m long) and four long cores (approximately 2.3 m long) were recovered from three different locations of the lake in a proximal to distal transect. Laminations in these cores are typically sub-millimeter in scale, and their structure is nicely revealed in thin section. Color and grain size changes define clay and silt couplets that are sub-millimeter to 5 mm in thickness. These couplets become significantly thinner down-core, interrupted by occasional fine-sand layers 1-3 mm thick. At the most proximal site, silt layers dominate core tops, and clay layers become relatively more abundant with depth. Laminations correlate between different cores from the same local basin as well as between cores from locations 0.5 km apart. Radiocarbon dates are forthcoming, but a tentative correlation of loss on ignition results to previously dated sediment cores from Lake Linnč suggests that the new cores extend through the past 2000 years. If this correlation is correct it indicates that the sediments are annually layered and contain a detailed record of the latest Holocene changes. Carbonate and organic matter content of the cores show an inverse correlation, which can be directly related to the health of the glacier as more coal-rich bedrock seems to be eroded with glacial advance. Magnetic susceptibility results indicate that no tephra layers made it to Linnč from Icelandic eruptions, but smaller decadal and centennial changes are present due to changes in local climate and sedimentation. Ongoing monitoring of modern sedimentation and Linnč glacier changes by the Svalbard REU program are helping to define the sedimentary signature of the late Holocene and recent environmental changes contained in these new sediment cores.