Holocene glacier fluctuations and environmental changes in sub-Antarctic South Georgia inferred from a sediment record from a coastal inlet

The sub-Antarctic island of South Georgia provides terrestrial and coastal marine records of climate variability, which are crucial for the understanding of the drivers of Holocene climate changes in the sub-Antarctic region. Here we investigate a sediment core (Co1305) from a coastal inlet on South Georgia using elemental, lipid biomarker, diatom and stable isotope data to infer changes in environmental conditions and to constrain the timing of Late glacial and Holocene glacier fluctuations. Due to the scarcity of terrestrial macro-fossils and relict organic matter in the sediments, age control was obtained by compound-specific radiocarbon dating of mostly marine derived n-C16 fatty acids. A basal till layer recovered in Co1305 was likely deposited during an advance of local glaciers during the Antarctic cold eversal. After glacier retreat an oligotrophic lake occupied the site, which transitioned to a marine inlet around 8.0±0.9 ka due to relative sea level rise. From 7.0±0.6 to 4.0±0.4 ka reduced vegetation coverage in the catchment as well as high siliciclastic input and deposition of ice rafted debris indicate glacier advances in the terrestrial catchment and likely in the adjacent fjord. A second, less extensive period of glacier advances occurred in the late Holocene, after 1.8±0.3 ka.