Neotectonics in Lago Roca, Santa Cruz province, Argentina

Lago Roca is located in southwestern Santa Cruz Province, Argentina, ∼40 km southwest of El Calafate, within Los Glaciares National Park. The study area lies within the internal fold-and-thrust belt of the Austral Basin, a structurally complex region shaped by N-S oriented thrusts and folds and intersected by NE-SW trending transfer zones 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 potential for ongoing neotectonic activity, which remains poorly constrained. This study aims to improve knowledge of recent tectonic activity in Lago Roca and its implications for local geological hazard. We reinterpreted existing high-resolution seismic profiles from the lake, analyzed a high-resolution digital elevation model of the surrounding subaerial 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 associated with normal and reverse faults affecting multiple sedimentary units. Additional normal faults mapped in the subaerial sector (S1–S4) are possible linked to the most recent event, while the SSDS in undisturbed units may correspond to the last event or an earlier one. Chronostratigraphic data constrain the onset of lacustrine sedimentation—and therefore deformation—to after 13,350–12,280 cal yr BP. The distribution of seismicity and structural trends suggests a genetic link between the observed deformation and neotectonic activity along the Lago Argentino Transfer Fault.