Exhumation history of the argentine eastern cordillera at 23° S. 25

LAPIANA AYELEN; SOBEL, EDWARD R.; CECILIA DEL PAPA; MONTERO LÓPEZ CAROLINA

Congreso; Latin- American Colloquium.; 2019

Universidad de Hamburgo

The onset of the Andean Orogeny in the Central Andes remains a topic of active research. Many studies investigating surface uplift gave concentrated 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 the 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, which lies adjacent to the west. It is characterized by three main mountain ranges and intermontane valleys with a NNE-SSW orientation and is delimited by fore- and back-thrust. These thick-skinned faults superimpose Precambrian to Ordovician basement rocks onto Mesozoic to Cenozoic sediments. Recent works have studied these major faults, as they represent the record of compressional activity since the Palaeogene (e.g., 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 fission track and (U-Th-Sm)/He analysis of apatites and zircons from the Aguilar, Mal Paso and Aparzo mountain ranges. The distribution of cooling ages and similar cooling patterns shown by the AHe, AFT, and ZHe chronometers show a rapid exhumation phase between 18 ? 7.5 Ma which we interpret to be caused by the increase of the Andean shortening. Exhumation and deformation were coupled in space and time at the eastern border of the northern Puna and throughout the Eastern Cordillera.