Crustal structure in the southern Andes, adjacent foreland, and Atlantic passive margin delineated by satellite gravimetric models

Abstract

Combined EIGEN-6C4 model and satellite-only GOCE data, both corrected by the topographic effect, allow analyzing the crustal structure of the transitional zone between the Southern Central and Patagonian Andes and adjacent foreland zone. We calculated gravity anomalies and vertical gravity gradients that allow inferring Moho depths and crustal structures that segment the basement. These data signaled important contrasts in crustal thickness, general anomaly patterns (e.g., roughnesssmoothness), and linear boundaries that characterize the main proposed terrains, parauchthoctonous microcontinents, and cratons that form the basement of the southern Andes. Even though roughly the obtained patterns follow previous proposals for the Southern Central Andes and adjacent foreland zone, limiting with high precision in particular the western Río de La Plata craton and Pampia-Cuyania-Chilenia microcontinents, an apparent higher complexity appears in Patagonia respect to previous models.In particular, a NW structure segmenting the North Patagonian Massif extending into the Atlantic platform and fore-arc region needs to be addressed in relation to the southern extent of the Chilenia microcontinent and the northern proposed suture of Patagonia. Additionally, The Famatinian suture that separates North and South Patagonia through the northern Deseado Massif shows a connection to the northern Malvinas plateau, which needs to be further verified. Over the Patagonia Andes, a strong segmentation between Chaitenia oceanic terrane, northern Magallanes basement and Scotia plate basement by means of oblique to the margin gradients needs also to be verified and interpreted tectonically.