Morphotectonic characterization in the Otumpa hills (Chacopampean plain, Argentina) from magnetotelluric data

PERI, VERÓNICA GISEL; POMPOSIELLO, M. CRISTINA; FAVETTO, ALICIA; BARCELONA, HERNAN

Buenos Aires

Seminario; XIV Giambiagi Winter School -Applied and Environmental Geophysics-; 2012

Departamento de Física, Facultad de Ciencias Exactas y Naturales, UBA

The Otumpa hills are located in the Chacopampean plain (Argentina), which is part of the Central Andean distal piedmont, above the western border of Las Breñas basin. The aim of this work was to obtain a morphotectonic characterization at different scales by magnetotellurics. Broad band NIMS equipment with flux gate magnetometers was used in order to perform a E-W profile located at 27° SL between 63º45? and 60º30? WL. The dimensionality of the electrical conductivity and distortion were analyzed by different methods to found the best geoelectric strike and distorted parameters. An anomalous zone was identified for periods greater than 100 seconds at most of the sites. So, the distortion was removed and the assumption of 2D regional structure was adopted. At deep, the 2D inversion model obtained showed two very resistive blocks (>10.000 Ω.m) that reaches 60 kilometers deeper that are separated by a conductive anomaly (60-100 Ω.m). The latter may be the austral expression of the continental Transbrasilian lineament associated with Neoproterozoic-Cambrian inferior belts. Also, the very resistive features at eastern and western sectors are interpreted as the Río de La Plata craton and Pampia terrane, repectively. The shallow features showed two sedimentary basins at the east and west extreme profiles. These basins are represented by 5 kilometers thick of conductive layers (3-50 Ω.m). Both are separated by a deeper high that shows a decrease of shallow conductive layers thickness. This depocenters represents Las Breñas and Alhuampa basins and the Otumpa hills are related to the deeper high between them.