­­PRELIMINARY ANALYSIS OF A HIGH-RESOLUTION LAKE-SEDIMENT RECORD SPANNING THE PAST 6400 YEARS FROM SOUTHWEST GREENLAND

Records of Holocene climate and environmental change spanning Greenland are important for paleoclimate forcing in ice sheet modeling. Few records exist from around the periphery of Greenland, however, that come close to matching the annual-resolution ice-core records from central Greenland. We report preliminary analysis of lake-sediment cores recovered from Baby Loon Lake (informal name; 66.93°N, 50.14°W, ~180 m asl), a proglacial lake adjacent to the present ice-sheet margin in Southwest Greenland. A macrofossil-based radiocarbon chronology from our highest-resolution core indicates that 170 cm of post-glacial sedimentation initiated ~6,400 cal yr BP. The basic stratigraphy in cores from three different sub-basins of the lake consists of basal sand, followed by non-glacial organic-rich sediments, and capped with a few centimeters of silt representing the return of ice-sheet meltwater to the lake. The organic-rich sediments are dark brown to black in color and are interrupted by sub-millimeter-scale light-colored laminations, suggesting little to no bioturbation. We characterize the sediments with 1-cm-resolution magnetic susceptibility, color reflectance spectrophotometry and loss-on-ignition, and 200-μm-resolution elemental data measured with ITRAX. The ITRAX titanium values sensitively record the light-toned laminations within the stratigraphy, which we currently interpret as eolian-derived. The increasing mineral component since ~500 AD, but prior to the lake’s transition to its current pro-glacial condition at ~1250 AD, may reflect the approaching ice margin and increasing adiabatic wind, causing eolian silt deposition in the lake. These and additional results to be presented provide a framework for future downcore proxy data generation that would lead to an increase in the number and spatial coverage of high-resolution Holocene climate datasets available from Greenland.