BIOMARKER ANALYSIS OF BAFFIN BAY SEDIMENTS TO DETERMINE LATE PLEISTOCENE PALEOCLIMATIC CHANGES IN GREENLAND

The climate of Greenland has undergone many periods of change during the Pleistocene. It is critical to evaluate how the Greenland ice sheet responded to climate change as the amount of melting directly affects sea-level changes. We analyzed 14 samples collected during IODP Exp 344S from Melville Bay off the NW coast of Greenland. 12 samples are from a 2.81m core section from Site U0061A and 1 each from Sites U0070A, and U0047A, located to the east and west of Site U0061A. Sediment ages are estimated to span 0-109.8kyr, based on a maximum age of 0.781Ma for the 19.99m section at Site U0061A. The sediments are comprised primarily of light-brown glaciomarine muds with microfossils grading into darker-brown sandier clast-bearing muds, interpreted to be proximal to a glacial front. A notable change occurs from 0.7-1 mbsf where the sediment changes in color and grain size. We use n-alkane distributions to reconstruct the vegetation and probable ice cover. Our preliminary n-alkane data from 3 samples shows large peaks at C18 and C20 and smaller peaks at longer chain lengths (C25-C31). Our calculated Carbon Preference Index (CPI) values for C24-C34 range from 1.52 to 1.97. The CPI values of <2.5 indicate mostly altered terrestrial material either through soil microbes or hydrocarbon addition. The short-chain n-alkanes like C18 indicate the presence of marine organisms and bacteria. Terrestrial plants produce long chain-length n-alkanes which can be sourced from leaf waxes and/or eroded terrestrial deposits (e.g. soils, land plants). The presence of C29-C31 indicates that there may have been small terrestrial inputs, which may be related to seasonal variations in NW Greenland. Primary productivity was likely restricted when Melville Bay was ice-covered during the last glacial period, leading to the transport of terrestrial-derived materials, like soil as ice-rafted debris. Our preliminary results indicate both marine and terrestrial inputs, but these samples are in the lower, darker part of our core section. We expect the marine signal to become even more dominant towards the top of the core, where the lithology indicates open glaciomarine conditions conducive to marine phytoplankton production. Future work with the 11 remaining samples will provide further details on the freeze-and-thaw cycles that are present in Greenland.