Unveiling terrane boundaries and basin geometries through satellite gravity field derivatives in the central region of Argentina

Abstract

Geodynamic and tectonic processes along the western margin of Gondwana during the Cretaceous, led to fragmentation of this supercontinent, and to the formation of South America and Africa as the South Atlantic opened. This complex event also affected paleo-terrane suture zones within the South American continent leading to the formation of a series of NNW intracratonic sedimentary depressions across central Argentina. The emplacement of these paleo-cratonic blocks has been described by V. A. Ramos (e.g. Ramos 1988; 1999; Ramos and Vujovich 1993; Ramos et al. 2010; 2014a; 2014b; 2020). His work has been crucial to the understanding of the tectonic processes and has also been referenced by numerous studies analysing terrane boundaries and basin distribution. Yet, the regional-scale geometry and location of the boundaries between the terranes, as well as of the depressions, based on geophysical data are scarce and/or remain imprecise. Combined Earth gravity field models derived from satellite and terrestrial data have been used to accurately map terrane boundaries and basin geometries (Braitenberg et al. 2011; Alvarez et al., 2012; Mariani et al. 2013; Christianse et al., 2021). The homogeneous data coverage of the GOCE (Gravity field and steady-state Ocean Circulation Explorer) derived models (Bruinsma et al. 2013) and the high resolution of the EIGEN-6C4 (European improved Gravity model of the Earth by New technics) model (Förste et al. 2014), which combines GOCE satellite data and terrestrial acquired data, allowed mapping at a larger scale with higher resolution and improved precision. We used in this work the Gravity Disturbance (Gd) and the Vertical Gravity Gradient (Tzz) data sets from both Earth gravity models to highlight basin geometries and different terranes boundaries in central Argentina. Both data sets were corrected by the effect of topography. The Gd were corrected by sedimentary load. The geologic features highlighted by the gravity derivatives match the terrane-cratonic block emplacement proposal of Ramos et al. (2010) for the central region of Argentina. Our interpretation of the Río de La Plata Craton (RPC) borders agree with the proposals of Rapela et al. (2011) and Oyhantçabal et al. (2011) regarding the eastern and western borders. However, significant differences are observed in the northern and southern borders.