Structure, seismostratigraphy, and tectonic evolution of Lago Roca (Southern Patagonia, Argentina)

Abstract

Lago Roca is a NE–SW elongated lacustrine body located to the south of Lago Argentino, the largest lake of the UNESCO ‘Los Glaciares’ National Park. An extensive high-resolution seismic survey carried out within the Lago Roca, integrated with geological information gathered in the area, have allowed to produce: (a) a complete bathymetric map of the lake; (b) a basement topography map and a structural map; and (c) an analysis of the geometry, distribution, and thickness of the sedimentary infill. Two sub-basins were recognized in Lago Roca, separated by a central basement high that shows a pop-up structure. The northern and southern margins of the lake basement are bounded by NE–SW trending strike-slip faults that constitute subsidiary faults strands of the regional structural lineament known as the ‘Lago Argentino transfer fault’. The shallow, low magnitude seismicity recorded in the area supports the interpretation that this fault segment is active at the present. The relative motion along the fault led to the deformation of the sedimentary infill of the lake, which was also affected by several subsidiary normal faults oriented parallel to the Lago Argentino transfer fault. Data show the peculiar asymmetry in the sedimentary filling of Lago Roca, typical of those of pull-apart basins generated along transform margins. A simplified model for the evolution of Lago Roca is also here proposed, based on the analysed data and the regional tectonic background.