Structural style and tectonic evolution of the Villa Unión-Tucumanesas high: a Pampean oblique structural zone, north Villa Unión-Ischigualasto Basin, La Rioja, Argentina

CANELO, HORACIO N.; GIMENEZ M; DÁVILA, FEDERICO M.; MARTIN B. WALSH; SANCHEZ-NASSIF, F.; JOSÉ L. TAILLANT

La Rioja Capital

Simposio; XVII Reunión de Tectónica La Rioja 2018; 2018

UNLaR │ Universidad Nacional de La Rioja - COMTEC ?AGA │Comisión de Tectónica de la Asociación Geológica Argentina

Geological mapping, structural analyses, gravity and seismic reflection data were used to characterize the style and tectonic evolution of the Villa Unión-Tucumanesas basement high, a subsurface feature located in the northern border of the Ischigualasto-Villa Unión Basin (IVB) of the western Sierras Pampeanas.The results show that the northern border of IVB is bounded by two WSW-ENE to SW-NE trending and SE-vergent reverse blind fault zones that imbricated basement creating fault-propagation folds, obliquely oriented to the typical N-S trending thick-skinned ?Pampean? structural style. Fault-slip data and structural seismic interpretation indicate that the study area records NW-SE shortening related to transpression distributed along oblique-slip thrusts and NW trending en echelon folds, during the Miocene-Pliocene to recent times as demonstrated by syntectonic (growth) strata and tilted alluvial pediments. However, to the east of the study area (Tucumanesas farm) typical ~N-S fault propagation folds develop. The latter suggests deflections in shortening directions related to lateral ramps, that could include local reactivation of weak supracrustal shear zones on a high-density/susceptibility upper crust (Grenville age basement ?) or ophiolitic sequences as proposed (Weidman et al. 2015), using 2d inverse magnetic and gravity models.