Morfotectónica en la quebrada de la Burra, Precordillera Central de San Juan. Argentina

LAURA P. PERUCCA; HORACIO N. VARGAS; LUIS MARTIN ROTHIS; CARLOS ALLIS

San Miguel de Tucumán

Congreso; XX Congreso Geológico Argentino; 2017

Facultad de Ciencias Naturales e Instituto Miguel Lillo, Universidad Nacional de Tucumán - Segemar

This work describes new structures with evidence of quaternary tectonic activity in a sector of the Central Precordillera. These structures are located in the eastern piedmont of the Sierra de la Crucecita, and western piedmont of the sierra de Talacasto, about 70 km northwest of San Juan, Ullum department (30° 54 '- 31° S and 68° 47'- 68° 55'W). By means of the neotectonic analysis we identified the main faults with quaternary tectonic activity located in both piedmonts, denominated from north to south: Las Crucecitas and Vertientes (in the eastern piedmont of the sierra de La Crucecita)and the Western Talacasto fault system (in the western piedmont of the homonymous sierra).The faults affect alluvial deposits assigned to the Pleistocene and Holocene and are defined by a series of features typical of compressive environments such as favor-slope scarps (eastern piedmont of the Sierra de La Crucecita) and counter-slope scarps (western piedmont of the sierra de Talacasto), fluvial terraces restricted to the hanging block of faults, sag ponds, aligned springs, diverted and obstructed drainage, deeply incised and sinuous in the hanging blocks, alluvial fans with anomalous slopes, among other features that evidence their Quaternary activ- ity. Four Quaternary alluvial levels were identified, Q1 the most recent and Q4 the oldest, according to their relative position, presence or absence of desert varnish and pavement and degree of incision. The faults affect Q4 to Q2 al- luvial levels in coincidence with the structural style of Central Precordillera. This deformation is related to the regional tectonics that affected and currently affects the Precordilleran area.