Sediment production in the Coastal Cordillera of Chile from detrital apatite geochemistry and thermochronology

We study spatial patterns of sediment production in two catchments of the Coastal Cordillera (Chile) situated in semi-arid and mediterranean bioclimates. To do so, we measure bedrock and detrital apatite trace elements as well as apatite cooling ages with the U/Pb, fission track, U-Th(-Sm)/He thermochronometric systems. The compositional and geochronologic data measured in bedrock are run through a Principal Component Analysis and a Support Vector Machine clustering algorithm to find the parameters that are best suited to trace sediment provenance at sub-catchment scale. Next, we analyse the distribution of the same parameters within the detritus to infer the relative contribution of different areas of the catchments. We find that spatial variations of bedrock cooling age and geochemical composition are significant even within small-scale (10-100 km2) monolithological catchments. Therefore, the combination of detrital apatite geochronology and geochemistry allows discrimination among source areas with acceptable confidence. This methodology has the potential to identify the main drivers of centennial to millennial sediment production, which will be tested in the following research steps.