A PALEOCLIMATE RECONSTRUCTION OF LAKE LINNé: INTERPRETING THE INFLUENCE OF SEDIMENT SOURCES THROUGH TIME

Spitsbergen, located at 76.5° to 80°N latitude in the High Arctic, is particularly sensitive to climate forcing, making it a good place to study climate trends. Lake Linné is one of Spitsbergen’s largest lakes (4.7 km long and 35 m deep) and is fed by the Linné Glacier. The Linné Glacier erodes from the coal-bearing Billefjorden sandstone, while the Gipshuken carbonate and Heckla Hoekphyllite series stretch along the eastern and western shores of the lake, respectively. Lake Linné’s sediments contain annual varves that are characterized by brown, gray, pink and tan laminae and can be used to produce climate models of the Linné Valley.

The age model produced by Nelson (2010) based on a core in the middle of the main basin (35 m depth) is inconsistent with that produced by Dowey (2013), who analyzed a core in the southern part of the main basin (30 m depth). One possible reason for this discrepancy may be due to including laminae associated with mass-movement events, rather than glacial activity, into age models.

In this study we used ITRAX high-resolution XRF to analyze changes in elemental signatures throughout Dowey (2013)’s core, a core obtained from the same location as Nelson (2010) and a core from the distal northern end of the lake (35 m depth). 14 large spikes in the calcium signatures of all cores correlate in depth to pink and tan laminae observed in the core stratigraphy. The X-radiographs of the cores further reveal that these peaks are associated with areas of high density.

EDS and BSE analyses found small (4-20 µm long) carbonate grains only to be present in the graded pink and tan layers and surrounded by angular quartz grains (up to 100 µm long). Since carbonate grains weather easily, their presence suggests that they originated from a proximal source and were deposited quickly. A fining-upwards of angular silica grains in these laminae further suggests that these layers are associated with mass depositional events. In contrast, the brown and gray laminae are composed of needle-shaped phylosilicates and do not contain carbonate grains. This is consistent with the composition of the Billefjorden and Heckla Hoek signatures, suggesting that these layers are associated with glacial activity. To improve on future varve-based age models of cores from Lake Linné, we therefore recommend the removal of the tan and pink calcium-rich laminae.