Radionuclides and soil properties as indicators of glacier retreat in a recently deglaciated permafrost environment of the Maritime Antarctica.

Many ice-free environments in Maritime Antarctica are undergoing rapid and substantial environmental changes in response to recent climate trends. This is the case of Elephant Point (Livingston Island, South Shetland Islands, SSI), where the glacier retreat recorded during the last six decades exposed 17% of this small peninsula, namely a moraine extending from the western to the eastern coastlines and a relatively flat proglacial surface. In the southern margin of the peninsula, a sequence of Holocene raised beaches and several bedrock plateaus are also distributed. A main issue in this environment is the role of glacier retreat and permafrost controlling the recently formed soils. To this purpose, a total of 10 sites were sampled along a transect crossing raised beaches and moraine materials following the direction of glacier retreat. At the selected sites surface samples were collected until 12cm depth and sectioned at 3cm depth intervals to analyse main properties, grain size, pH, electrical conductivity and carbonates. Besides, elemental composition and fallout (FRNs) and environmental radionuclides (ERNs) were analysed. To assess if profile characteristics within the active layer are affected by glacier retreat variations of organic carbon and carbon fractions and137 Cs contents were examined. The presence of organic carbon (range: 0.13-3.19%), and137 Cs (range: bdl-10.1Bqkg-1 ) was only found at the raised beaches. The surface samples had abundant coarse fractions in rich sandy matrix with increasing acidic pH towards the coast. Significant differences were found in the elemental composition and the radionuclides between the moraine and raised beaches. Soil forming processes are related to the time of exposure of the landforms after glacier retreat. The results obtained confirm the potential for using geomorphological, edaphic and geochemical data to assess the influence of different stages of glacier retreat in recent soils and sediments.