Exhumation history of the Argentine Eastern Cordillera at 23ºS

LAPIANA, AYELÉN; MONTERO LÓPEZ, CAROLINA; SOBEL, EDWARD; ZAPATA, SEBASTIÁN; DEL PAPA, CECILIA

Hamburgo

Simposio; 25th Latin-American Colloquium of Geoscience; 2019

The onset of the Central Andes Orogeny remains a topic of active research. Many studies investigating surface uplift are concentrate on the region between 22° - 26° S (see Reiners et al., 2014). They mostly focus on the Cordillera de Domeyko, Coastal Cordillera, the southern Puna - Eastern Cordillera and the Sierras Pampeanas, while very little information is available from the northern Puna to Eastern Cordillera (Deeken et al., 2005; Haschke et al., 2005; Insel et al., 2012; Reiners et al., 2014). The Eastern Cordillera at 23°S consists of a narrow zone up to 100 km wide with more pronounced structural relief than the Puna lying adjacent to the west. It is characterized by three main mountain ranges and intermontane valleys with a NNE-SSW orientation and is delimited by thrust and backthrust faults. These faults superimpose the Precambrian to Ordovician basement rocks onto Mesozoic to Cenozoic sediments, resulting in thick-skinned tectonic style deformation. Recent works have studied these major faults, as they interpret compressional activity since the Palaeogene (Coutand et al., 2001; Monaldi et al., 2008; Insel et al., 2012; Montero-López et al., 2018). In order to investigate the temporal and spatial exhumation pattern of this part of the Andes we present consisting thermochronological data supported by fission track and (U-Th-Sm)/He analysis on apatites and zircons of an W-E transect from the Aguilar, Mal Paso and Aparzo mountain ranges. The distribution of cooling ages and similar cooling pattern from the AFT- ZHe and AFT- AHe chronometers shows a rapid exhumation phase between 18 ? 7.5 Ma caused by the increase In shortening coincident with the main phase of Andean deformation. Exhumation and deformation were coupled in space and time at the eastern border of the northern Puna and throughout the Eastern Cordillera.