Topographic evidence for recent intraplate reactivation in NW Uruguay

Mauricio Barcelos Haag , Lindsay M. Schoenbohm, Rossano Dalla Lana Michel, Claiton Marlon dos Santos Scherer , Gerardo Veroslavsky, Josefina Marmisolle

Located in eastern South America, Uruguay has been considered tectonically inactive since rifting in the Cretaceous. Here, we use a high-resolution digital elevation model (DEM) and field observations to investigate the presence of recent tectonic activity in the Basaltic Plateau, northwest Uruguay. Based on topographic-, drainage network- and field-based data, we identify evidence for long-lasting, and potentially ongoing/recent (Cretaceous-Cenozoic) tectonic deformation, including fault breccia, scarps, and offset channels, indicative of potential normal and strike-slip deformation. The orientation and spatial pattern of this deformation aligns closely with inherited structures, particularly Proterozoic and Mesozoic fault zones. Our results suggest that reactivation of ancient basement structures has localized recent deformation, highlighting the importance of tectonic inheritance in controlling deformation in intraplate regions considered otherwise tectonically “inactive”. The detection of subtle, recent deformation in Uruguay is only possible because of high-resolution topographic data, underscoring the role of modern remote sensing tools in assessing tectonic activity in presumed stable regions. Lastly, this study highlights the need to reassess intraplate landscapes for signs of recent deformation, particularly in regions underlain by major basement structures that may act as zones of weakness, facilitating deformation even under minor stress conditions.