Tectonic structures of SW margin of Gondwana from gravity and magnetic anomalies of the Río de la Plata area and their correlation with the Beattie magnetic Anomaly in South Africa

Abstract

The Río de la Plata cratonic area and the adjacent continental platform (South America) have been subject of geophysical and tectonic studies for several decades. However, there are still many uncertainties related with its structural configuration and tectonic evolution. To deepen the knowledge of the tectono-structural characteristics of the cratonic and surrounding areas, we carried out an analysis of magnetic and gravity anomalies, which is highly effective in accurately locating the boundaries of crustal/lithospheric domains/terrains and structures. Additionally, this tectonic characterization allows us to correlate South American geophysical features with their counterparts in southern South Africa (i.e., Beattie Magnetic Anomaly).

In this study, different filters and techniques were employed to analyze magnetic and gravity anomalies. The gravity anomaly was obtained from global models, whereas the magnetic anomaly was compiled from diverse sources (aerial, terrestrial, and marine data). Particularly, the first vertical derivative, total horizontal derivative, analytic signal, tilt angle and upward continuations were calculated, and 3D Euler Deconvolution was applied.

Our results confirm the existence, and accurately determine the location, of Río Negro and Colorado transfer zones, Sierra de la Ventana Shear Zone, and extensional structures in the Tandilia System area, here defined as Tandil Trough. Moreover, we propose that the Sierra de la Ventana Shear Zone was shifted northwards in the offshore sector of the study area through sinistral displacement along the Punta Mogotes Shear Zone. Considering the similar rheological contrasts exhibited by the South African margin, we suggest an analogous configuration in the case of the Cape Fold Belt. Additionally, based on our interpretations, and considering previous geophysical studies, we support the proposal that the Beattie Magnetic Anomaly in South Africa and the magnetic anomaly detected beneath the Claromecó Basin would be generated by comparable sources (i.e., Sierra de la Ventana Shear Zone).