The AP alluvial deposition occurred in two spatially and temporally separated episodes of alluvial backfilling: 1) shortly before ~20.14 Ma and to prior to ~9.4 Ma, a timespan that allows for the drainage capture of the eastern Precordillera, and considerable landscape rearrangement 2) post ~9.4 Ma, with a re-positioning of alluvial backfilling from the Precordillera towards the Central Depression. Results show that the evolution of the AP is a long-term and continuous process (from >20 to ~2.3 Ma) of alluvial deposition and subsequent alluvial plain formation developed by interplay between the climate variability of the Atacama Desert and Andean uplift. In this study we perform geomorphologic and stratigraphic observations on the AP in the Salado Canyon area, combining new geochronological results derived from ⁴⁰Ar/³⁹Ar biotite ages from volcanic layers interbedded within the alluvial deposits, and ²¹Ne exposure ages on quartz-clasts on alluvial plains, to determine the chronology of the AP evolution. The Atacama Pediplain (AP) extends over >12,000 km² (26° to 28°S Lat) through the Central Depression and Precordillera of the southern Atacama Desert. In the Atacama Desert, pediplains are generally used as morphotectonic markers to define the chronology of episodes of Late Cenozoic Andean uplift from their erosion and incision patterns and timings. Pediplains are classically identified as flat landscape surfaces in arid regions linked to tectonic quiescence, whereas deep incision of a pediplain is attributed to tectonic uplift. This interpolation reveals the main pattern of the Moho surface, avoiding short wavelength variations (Fig. We perform a new interpolation of the Moho surface from Chevrot et al.'s dataset, using the 3D GOCAD modeler (Mallet, 2002). (2014), which involves recent receiver functions data and reflection-refraction profiles from France and Spain (see references in Chevrot et al., 2014). We compare the Moho depths with the dataset from Chevrot et al. 3 shows three models involving variable crustal densities (Table 1). The crustal density linearly increases with depth, and the density of the lithospheric mantle is temperature dependent. It also considers a four-layered density model composed of atmosphere/sea water, crust, lithospheric and astheno- spheric mantle. Our modeling approach assumes that (1) local isostasy is verified, considering a depth of compensation of 300 km, and (2) the system is in thermal equilibrium. In order to avoid sub-lithospheric density variations, we filtered the geoid so that the signal corresponding to the lower spherical harmonics until degree and order 10 is ruled out. order to compare independently geophysical approa- ches for the calculus of the depths of the Pavlis et al., 2008).
0 kommentar(er)
