Un modelo gravimétrico 3D de la profunda cuenca sedimentaria de Ischigualasto-Villa Unión (San Juan y La Rioja)-Argentina

Abstract

A real gravimetric surveys were carried out in the Ischigualasto-Villa Unión intermontane deep basin, the north of the Andean Precordillera, and in a wide portion of the western Sierras Pampeanas. Maps of Bonguer anomalies (AB) and Bouguer anomalies "affected by geological reduction" (ABcg) were derived from the observed data. The basin is located in a complex tectonic setting that strongly contaminates the gravity field. The present study aims to interpret the 3D geometry of the sedimentary basin through gravity data analysis. The separation of the gravimetric effect of the sedimentary filling is a complex task presently solved by employing: i- a graphical smoothing method from AB; and ii- numerical filterings from ABcg (AB corrected by the sedimentary filling effect of neighboring basins). This analysis permits to deduce that in the center and north of the basin the gravity anomalies should be mainly the result of the sedimentary filling effect, whereas in the south of the basin positive effects in the crust prevail due most likely to mafic intrusive rocks. A gravity model supported by seismic data that provides sedimentary thicknesses of up to 9 km in the central region of the basin was formulated by using gravimetric inversion of the residual anomaly.