Detrital low thermochronology applied to moraine deposits in the central Patagonian Andes

Over geological time scales, tectonics and climate exert a first-order control on erosion distribution and efficiency, thereby influencing the evolution of fluvio-glacial mountainous landscapes. This is particularly the case in the Patagonian Andes, a tectonically active region spanning more than 1500 km from North to South. The present landscape has been significantly impacted by the action of erosion and tectonics over different glacial/interglacial cycles during the last 5-6 Ma. Rock cooling history for the region has been previously inferred from bedrock low-temperature thermochronology, whose representativeness may be questioned, as large areas are currently inaccessible, notably due to the presence of ice. Here, we make use of glacial deposits (terminal moraines) that are well preserved in the present landscape, to retrieve information on the erosion history of the region assuming that these deposits are representative of the entire glacial catchment. We present the first results of a multi-method approach applied to the General Carrera-Buenos Aires Lake (GCBA) area, including: (1) apatite fission track (AFT) and U-Pb double dating of samples collected within different moraine complexes east of the GCBA lake, and (2) inverse thermal history modeling using our new detrital data and available in-situ low-temperature thermochronological data. The inference of the thermal histories involves the prediction of elevation profiles, the estimation of detrital age distributions, and the inference of a topographic sampling function (TSF) for each detrital sample. Dating of detrital apatites reveal numerous AFT ages that are older than those observed in in situ/bedrock data from the same glacial catchment. Inverse modelling suggests that these older AFT ages are likely to have sourced from areas at high elevation. We further explore the potential causes for the observed differences in age distributions, which may include: (a) potential biases in the separation process, (b) differences in erosion processes through the catchment, (c) differences in sediment transport and storage processes.