Strong positive residual gravity anomaly in the Famatina system and its relationship with ancient sutures: alternative explanations

Abstract

A gravity profile located in La Rioja province (Argentina) at an approximate latitude of 29° S. was analysed. Application of gravimetric methods of maximum depth shows that, under the Famatina Range, the anomaly of mass is located in lower crust. By contrast, in the Velasco Range, the maximum depths of the anomalous masses are within the upper crust, a result in total agreement with previous results. The significant correspondence between the geological structures and the gravity field was alalysed. The gravity signal reveals clearly the zone of the suture present between the Precordillera and the Sierra of Famatina, as well as the shears zone between the Famatina and Velasco ranges. Using our geophysical results and previous geological investigations, we propose a collision model (II Cortical Model) that describes the relationship between the Chilenia, Cuyania, Famatina and Pampia terranes. This model agrees closely with the observed Bouguer anomaly.