Holocene compression in the Acequion valley (Andes Precordillera, San Juan province, Argentina): Geomorphic, tectonic, and paleoseismic evidence

FRANCK ALBERT AUDEMARD; LAURA P. PERUCCA; ANA PANTANO; CARLOS ROBERTO AVILA; MARÍA ROMINA ONORATO; HORACIO NICOLÁS VARGAS; PATRICIA ALVARADO; HEWART VIETE

JOURNAL OF SOUTH AMERICAN EARTH SCIENCES

PERGAMON-ELSEVIER SCIENCE LTD

Lugar: Amsterdam; Año: 2016 vol. 67 p. 140 - 157

0895-9811

The Matagusanos-Maradona-Acequion Valley sits within the Andes Precordillera fold-thrust belt ofwestern Argentina. It is an elongated topographic depression bounded by the roughly NeS trendingPrecordillera Central and Oriental in the San Juan Province. Moreover, it is not a piggy-back basin as wecould have expected between two ranges belonging to a fold-thrust belt, but a very active tectoniccorridor coinciding with a thick-skinned triangular zone, squeezed between two different tectonic domains.The two domains converge, where the Precordillera Oriental has been incorporated to the SierrasPampeanas province, becoming the western leading edge of the west-verging broken foreland SierrasPampeanas domain. This latter province has been in turn incorporated into the active deformationframework of the Andes back-arc at these latitudes as a result of enhanced coupling between theconverging plates due to the subduction of the Juan Fernandez ridge that flattens the Nazca slab underthe South American continent.This study focuses on the neotectonics of the southern tip of this NeS elongated depression, known asAcequion (from the homonym river that crosses the area), between the Del Agua and Los Pozos rivers.This depression dies out against the transversely oriented Precordillera Sur, which exhibits a similartectonic style as Precordillera Occidental and Central (east-verging fold-thrust belt). This contributionbrings supporting evidence of the ongoing deformation during the Late Pleistocene and Holocene of thetriangular zone bounded between the two leading and converging edges of Precordillera Central andOriental thrust fronts, recorded in a multi-episodic lake sequence of the Acequion and Nikes rivers. Theherein gathered evidence comprise Late PleistoceneeHolocene landforms of active thrusting, fault kinematics(micro-tectonic) data and outcrop-scale (meso-tectonic) faulting and folding of recent lake andalluvial sequences. In addition, seismically-induced effects already reported in the literature by thisworking team further support the tectonic activity of neighboring faults in the Holocene. As a concludingremark we could state that the ongoing deformation in the region under study is driven by acompressional regime whose maximum horizontal stress in the late PleistoceneeHolocene is roughlyeast-west oriented. This is further supported by focal mechanism solutions.