ANISOTROPY OF MAGNETIC SUSCEPTIBILITY AND KINEMATIC ANALYSIS IN DEFORMED NEOGENE SEQUENCES, NW SIERRAS PAMPEANAS (27°30´S): PRELIMINARY RESULTS

QUIROGA, RODRIGO; MATÍAS PEÑA; LAURA GIAMBIAGI; SURIANO; JOSÉ MESCUA; SEBASTIÁN PERROUD

Rancagua

Simposio; Sexta Reunión Bienal LATINMAG. Asociación Latinoamericana de Paleomagnetismo y Geomagnetismo.; 2019

Universidad de O?Higgins

We present preliminary results of AMS and kinematic analysis of Neogene deformed sequences exposed inPrecordillera and northwest Sierras Pampeanas (27°30´S). The AMS analysis from 30 sites show a widerange of foliation degree, between sedimentary to tectonic. The kinematic analysis, in more than 500mesoscopic-scale faults, show, principally, a contractional and a strike slip event. The magnetic lineationand foliation is well developed near to the meso- and large-scale structures and K1 orientation is parallel tothe main fold axes and inverse faults that affected the Neogene sequences. Kinematic analysis shows, inPrecordillera (Fiambala Basin), a contractional event with E-W major direction from ~9-8 Ma. NW and NEstrike-slip faults affect all the Neogene sequences, suggesting a later (after 3 Ma) strike-slip event in thebasin. While in NW Sierras Pampeanas, the deformation is predominantly contractional since ~15 Ma. Bycomparing the AMS and kinematic analysis results, we obtain a timing for syn-lithification and postlithificationstrain field. In this way, we compare both broken foreland intermontane and foreland basins tounderstand spatio-temporal strain variations.