Reconstructing Late Pleistocene air temperature variability in SW-Britain based on branched GDGTs in the sedimentary record of Llangorse Lake (Wales)
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Llangorse Lake, Wales, is a lake which formed after the glacier retreat following the LGM, upstream in the Afon Llynfi valley, at the edge of the River Wye catchment. The lake has been previously cored, from which it was shown that it contained sediments older than the Preboreal, which is the oldest date currently available for Llangorse Lake sediments. Using a combination of loss on ignition (LOI) – and organic geochemical analysis methods, an attempt is made to reconstruct Late Pleistocene air temperatures based on branched glycerol dialkyl glycerol tetraether (brGDGT) membrane lipids from bacteria living in soils and the water column. An end-member mixing model is proposed to separate the two sources of bacterial membrane lipids, which end up in the sedimentary archive. This correction method shows promising results for the applicability of brGDGT membrane lipids in lacustrine environments. The reconstructed temperatures show a comparable signature of Late Pleistocene air temperatures as found from other proxy methods and sedimentary archives.