Kinematic constraints on the dextral strike-slip El Tigre fault, Argentine Precordillera, on the basis of paleomagnetic and magnetic fabric studies

FAZZITO, SABRINA YESICA; RAPALINI, AUGUSTO ERNESTO; CORTÉS, JOSÉ MARÍA; TERRIZZANO, CARLA MARINA

Mérida

Congreso; The XIIth Scientific Assembly -IAGA 2013; 2013

IAGA

The El Tigre Fault, in the Western Precordillera of Argentina, is a 120 km long dextral strike-slip fault of Quaternary age. It is very well exposed and it is characterized by geomorphic markers of horizontal displacement as well as a conspicuous fault scarp in its central section that indicates a component of vertical movement. Several controversies with respect to the geometry and kinematics of the fault have not yet been solved. We present the results of a combined paleomagnetic and magnetic fabric study on Miocene to Quaternary sediments exposed very close to the fault trace. The paleomagnetic study was performed on 442 samples collected at 31 sites on Middle Miocene-Early Pliocene, Middle Pleistocene and Late Pleistocene sediments. The results show variable values of rotations around vertical axes, both clockwise and counterclockwise, that suggest that this section of the fault is segmented into several blocks. They can be modeled as forming a ?domino? general pattern of rotation with strong drag both along the main as well as secondary faults. Magnitudes of rotation are related to the age of the studied sediments, reaching largest values in some sites of Miocene strata. The magnetic fabric study was carried out by means of anisotropy of magnetic susceptibility (AMS) on 19 sites. Most sites showed magnetic fabric with tectonic overprint, despite the fact that they were generally collected from subhorizontal strata of poorly consolidated sediments with no macroscopic evidence of internal deformation. A change in the main regional shortening direction from WSW-ENE to W- E between the Middle and Late Pleistocene is suggested by the AMS data.