The La Puntilla - La Falda shear zone, Sierra de Umango, Western Sierras Pampeanas, Argentina: an example of high-temperature lateral ramp.

TIEPPO MEIRA, VINICIUS; CAMPOS NETO, MARIO; BASEI MIGUEL; GONZÁLEZ PABLO DIEGO; VARELA RICARDO

Campinas

Simposio; 13° Simposio Nacional de Estudos Tectonicos y 7° International Symposium on Tectonics.; 2011

Sociedade Brasileira de Geologia-Nucleo Sao Paulo

In the Pampean flat-slab, Central Andes, crops out basement blocks (Sierras Pampeanas) uplifted and rotated in the Cenozoic times. The Western Sierras Pampeanas is characterized by Grenvillian Mesoproterozoic meta-igneous aged rocks and metasedimentary units metamorphosed in the Ordovician Famatinian Orogeny, and it is considered the northern part of the Cuyania Terrane. The Sierra de Umango is the westernmost Western Sierras Pampeanas, limited by Devonian sedimentary rocks of Precordillera on the western side, separated by Tertiary rocks from the Sierra de Maz and Sierra del Espinal on the east, and with igneous and sedimentary rocks of Famatina System cropping out on the further east. It is composed of meta-igneous and metasedimentary rocks cropping out around the 29° S latitude and 68°30’ W longitude, on the southwestern La Rioja Province, Argentina. Eight geological units were distinguished in the Sierra de Umango: i- the basement unit Juchi Orthogneiss of Mesoproterozoic age; ii- metasedimentary units Tambillo (where the La Puntilla - La Falda Shear Zone – PFSZ – is included) and iii- Tambillito; iv- Ordovician syn-collisional El Peñon Granite; v- El Cordobés metamafic rocks Unit; vi- late-collisional Guandacolinos Granite and vii- post-collisional Cerro Veladero Granite; and viii- La Troya Marble. The PFSZ delineates a ~5 km wide stripe in the westernmost Tambillo Unit, determining the western boundary of the Sierra de Umango. A Nappe System associated to the Famatinian Collisional Event between the Cuyania Terrane and the proto-Andean margin of Gondwana characterizes the main structure of the Umango basement rocks, including the Juchi Orthogneiss Klippen. This report wishes to contribute to the understanding of the PFSZ kinematic and its geotectonic implications related to the collision of Cuyania Terrane against the proto-Andean margin of Gondwana.