Antithetic linkage between oblique Quaternary thrusts at the Andean front, Argentine Precordillera

The Quaternary orogenic front of the Andes at 32° 10'S is characterized by abrupt changes in the structural style and surface expression of recent deformation, due to the reactivation of inherited structures. North of 32° 10'S, Quaternary deformation is mainly expressed by NNE-trending west-verging thrusts belonging to the Eastern Precordillera. Whereas south of such latitude NNW-trending east-verging thrusts prevail, related to the Southern Precordillera. This framework determines an overlapping zone of antithetic thrusts, where Quaternary slip is transferred from one system to the other. The overlapping zone defined by these structures with oblique trend, determines a wedge-shaped geometry in plan view where deformation in the Quaternary alluvial cover indicates the reactivation of NNE-trending east-verging breaching faults over the entire overlapping stretch of the transfer zone. The documented Quaternary deformation points to a significantly higher activity and cumulative slip related to the east-directed structures. This style represents mixed characteristics of both interacting thrust systems and is interpreted to be the reactivation of pre-existing anisotropies during Quaternary shortening.