Neotectonic in the Neuquén Cordillera, northern part of the Neuquén Province: a review.

BRUNO COLAVITTO; ANDRES FOLGUERA; LUCÍA SAGRIPANTI; BÁRBARA LABEL; LUCÍA JAGOE

Santiago

Simposio; Primer Simposio de Tectónica Sudamericana; 2016

Asociación Tectónia Sudamericana

The Northern Neuquén Province between 37° and 38° lat S it is characterized by the development of two parallel fold and thrust belts. To the east the well studied Chos Malal fold and thrust belt (CMFTB) and to the west the Guañacos fold and trust belt (GFTB). Each of it have a particular tectonic evolution, on the one hand, the CMFTB have the most important uplifted stages during the Cretaceous and Miocene time. On the other hand, the GFTB formed in response to inversion of pre existing normal faults of the late Oligocene to early Miocene Cura Mallin basin during Miocene times. Both fold and trust belt have been reactivated during Pleistocene to Quaternary times, but each area have different triggering. The CMFTB presents evidence of young deformations that is related to asthenospheric anomalies. 3D inversion of magnetotelluric array data reveals an electrically conductive plume-like asthenospheric feature. This conductivity anomaly has a deep source (deeper than 300 km) and extends locally into the upper lithosphere. The shallowest conductivity features are closely associated with Tromen, Payun-Matru and Auca Mahuida volcanoes. There is a relationship between the distribution of Quaternary deformation in the foreland area and the conductivity anomalies. On the other hand, the GFTB is affected by the Antiñir Copahue fault system (ACFS) which constitutes the northern prolongation of the Liquiñe Ofqui fault system (LOFS). The LOFS runs through the Andean arc front for more than 1000 km from the triple junction at ~46° 30′S to ~37°S. This fault system projects locally into the eastern slope of the Southern Central Andes, crossing the axial mountain sector north of 38°S and continuing in the western retroarc area as the ACFS exactly where the GFTB reactivation are recognize. We suggest a connection between thermally-weakened crust, neotectonic deformation and fluvial morphology that together explain the abnormal pattern of young deformation in the Southern Central Andes. Unlike the Pampean-Chilean flat subduction zone (27°-33°S), where recent tectonic activity produces a continuous orogenic front, neotectonics in the northern Neuquén Cordillera is restricted to relatively short segments cutting inner and outer zones of the fold and thrust belt.