Records of the first Eocene Andean deformation at the Eastern Puna plateau border in Northwest Argentina

HONGN, FERNANDO; LÓPEZ STEINMETZ, ROMINA; STRECKER, MANFRED; MONTERO LÓPEZ, CAROLINA; DEL PAPA, CECILIA; PINGEL, HEIKO; ARAMAYO, ALEJANDRO; LAPIANA, AYELÉN

Hamburgo

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

The present-day transition zone between the northern sector of the Puna Plateau And the northern part of the Argentine Eastern Cordillera constitutes a key area for studying the onset of the Andean contractional deformation. Records of Middle Eocene syn-sedimentary deformation in response to the initial Andean shortening, reveals that reactivation of Paleozoic and Cretaceous structures and the development of doubly vergent thrusts are founded in both Puna and EasternCordillera. Detailed geological mapping and structural analyses along this transition zone show progressive unconformities, intra-formational unconformities and seismites. Moreover, provenance analyses on Paleogene sedimentary successions on the Puna Plateau suggest sediment transport from the Sierra Alta mountain range, which constitutes the present-day drainage divide between the Puna and Eastern Cordillera in the Jujuy province. In agreement with other regional studies, these features are strong evidence of an initial proto-relief since the Paleogene. Our study area is located along a regional N-S trending mountain belt, which is controlled by basement heterogeneities and extends from the Bolivian Eastern Cordillera to the Argentine Calchaquí valleys.Importantly, the Eocene crustal shortening was coeval with contractional events in northern Chile and Bolivia. This indicates a non-regular distribution of thePaleogene deformation and sedimentation in an unusually wide back-arc region, which is extended nearly 300 km - from the present-day arc to the western halfof the Eastern Cordillera.