Tracing thermal history of the central Patagonian Andes with detrital multi-dating of foreland basin deposits
Abstract
Detrital thermochronology in wide foreland basins documents erosion of
diverse sediment source areas along an adjacent orogen through time. This study
presents new detrital apatite thermochronology data (U-Pb and fission tracks) from the
whole central Patagonian foreland (44°S – 48 °S) that identify at first a persistent
volcanic input from Oligocene to late Miocene. The apatite U-Pb dating was effective to
discriminate AFT ages related to either the exhumation of the source or the volcanic
input, which can easily overtake the exhumation signal along the Patagonian Andes.
Lag time, calculated from the youngest AFT component (~30 Ma) and stratigraphically
constrained with new zircon U-Pb ages, indicates that the entire central Patagonian
Cordillera was probably in steady-state erosion at ca. 30 Ma until the resumption of
shortening during the late Neogene. Furthermore, these new detrital
thermochronological data emphasize a signal of low rate post-orogenic erosional
processes (0.1 – 0.4 km/Ma) corresponding to a significant unroofing of 2 – 4 km
between the Oligocene and the late Miocene; a period characterized by a relative
tectonic quiescence, subsequent to the late Early Cretaceous – middle Eocene interval
in which significant deformation took place.
This study identifies sediment contribution from different source areas to the
central Patagonian foreland and constrains the timing and rates of the post-orogenic
cooling along the central Patagonian Andes, thus defining great sediment sourcing from
the Andes in spite of tectonic quiescence.