Tracing thermal history of the central Patagonian Andes withdetrital multi-dating of foreland basin deposits

Abstract

National audienceDetrital thermochronology in wide foreland basins documents erosion ofdiverse sediment source areas along an adjacent orogen through time. This studypresents new detrital apatite thermochronology data (U-Pb and fission tracks) from thewhole central Patagonian foreland (44°S – 48 °S) that identify at first a persistentvolcanic input from Oligocene to late Miocene. The apatite U-Pb dating was effective todiscriminate AFT ages related to either the exhumation of the source or the volcanicinput, which can easily overtake the exhumation signal along the Patagonian Andes.Lag time, calculated from the youngest AFT component (~30 Ma) and stratigraphicallyconstrained with new zircon U-Pb ages, indicates that the entire central PatagonianCordillera was probably in steady-state erosion at ca. 30 Ma until the resumption ofshortening during the late Neogene. Furthermore, these new detritalthermochronological data emphasize a signal of low rate post-orogenic erosionalprocesses (0.1 – 0.4 km/Ma) corresponding to a significant unroofing of 2 – 4 kmbetween the Oligocene and the late Miocene; a period characterized by a relativetectonic quiescence, subsequent to the late Early Cretaceous – middle Eocene intervalin which significant deformation took place.This study identifies sediment contribution from different source areas to thecentral Patagonian foreland and constrains the timing and rates of the post-orogeniccooling along the central Patagonian Andes, thus defining great sediment sourcing fromthe Andes in spite of tectonic quiescence