Neotectonics in Lago Roca, Santa Cruz province, Argentina

Abstract

Lago Roca is located in southwestern Santa Cruz Province, Argentina, ~40 km southwest of El Calafate, withinLos Glaciares National Park. The study area lies within the internal fold-and-thrust belt of the Austral Basin, astructurally complex region shaped by N-S oriented thrusts and folds and intersected by NE-SW trending transferzones such as the Lago Argentino Transfer Fault. Although the region has been considered of low seismic hazard,shallow earthquakes of moderate magnitude (e.g., Mw 5.4 in 2021) have been recorded, indicating the potentialfor ongoing neotectonic activity, which remains poorly constrained. This study aims to improve knowledge ofrecent tectonic activity in Lago Roca and its implications for local geological hazard. We reinterpreted existinghigh-resolution seismic profiles from the lake, analyzed a high-resolution digital elevation model of the surroundingsubaerial area, and examined soft-sediment deformation structures (SSDS) in exposed lacustrine deposits.Our results identify at least four paleoseismic events preserved in the lake infill, expressed as Mass-Transport Deposits (MTDs), megaturbidites, and SSDS. These features are spatially and stratigraphically associatedwith normal and reverse faults affecting multiple sedimentary units. Additional normal faults mapped inthe subaerial sector (S1–S4) are possible linked to the most recent event, while the SSDS in undisturbed unitsmay correspond to the last event or an earlier one. Chronostratigraphic data constrain the onset of lacustrinesedimentation—and therefore deformation—to after 13,350–12,280 cal yr BP. The distribution of seismicity andstructural trends suggests a genetic link between the observed deformation and neotectonic activity along theLago Argentino Transfer Fault.