Glacial-related morphology and sedimentary setting of a high-latitude lacustrine basin: The Lago Chepelmut (Tierra del Fuego, Argentina)

Abstract

Lago Chepelmut is a relatively small lake in size, of ellipsoidal shape, located in the outer fold-andthrust belt of the Fuegian Andes (southernmost South America). High-resolution single-channel seismic profiles, integrated with geological information in the surrounding area, have allowed to reconstruct for the first time a bathymetric map of the lake and the architecture, distribution and thickness of the sedimentary cover. Two main seismic units were identified in the seismic records: (i) a Lower Unit of glacial nature, likely associated to the Last Glacial Maximum (LGM), and irregularly distributed through the basin, and (ii) an Upper Unit of lacustrine origin which drapes the entire basin. Submerged moraine deposits within the lake were also found from seismic data, and correlated with moraine arcs widespread distributed in the surroundings of the basin. These morphologies represent the recessional deposits left by the Ewan glacier lobe, one of the easternmost fronts of the Tierra del Fuego glaciers during the LGM. The lacustrine sedimentary record shows that the lake level was not constant through the recent history of the lake. Moreover, data analyses has shown that there is also an important structural component that has conditioned the evolution of the basin, in addition to that linked to glacial activity.

Depositional setting of the southern arms of Lago Argentino (southern Patagonia)

“…The result of this procedure was the compilation of two-way traveltime (TWT) grids with 0.001°spacing for: (i) the top of the acoustic basement, (ii) the top of the glacier unit: and (iii) the thickness of the glacio-lacustrine sequence. An analogous methodology was applied in the lakes of Tierra del Fuego, like Lago Fagnano (Esteban et al, 2014), Lago Yehuin (Lozano et al, 2018a), Lago Chepelmut (Lozano et al, 2018b) and Lago Roca (Bran et al, 2019).…”

The central Fuegian fold and thrust belt in Tierra del Fuego: Strike‐slip tectonics superimposed onto compressional deformation

“…Structural data from sections of published works were used as a regional framework for the arrangement of the compressional structures of the internal and external fold and thrust belt (Álvarez‐Marrón, McClay, Harambour, Rojas & Skarmeta, ; Menichetti et al, ; Torres Carbonell et al, , ). Other previous works which dealt with the development of structures associated with strike‐slip tectonics were also used to show the ZFYC near the external‐internal fold and thrust belt boundary (Lozano et al, , b).…”

“…The topographic correction for the Bouguer gravity anomaly was performed from the free air gravity anomaly grid and a topographic grid from the Shuttle Radar Topography Mission (SRTM) data. For complete the topographic data of the region, the bathymetry used is the GEBCO grid, which has a spatial resolution of 30 s (Weatherall et al, ) and the bathymetric data from Fagnano, Yehuin, and Chepelmut lakes (Esteban et al, ; Lozano et al, , b).…”

“…Although the origin of Yehuin and Chepelmut lacustrine basins has been related to the WNW‐ESE extensional faults developed during the Neogene, their evolution was also conditioned later by the ice‐carving of two glacier lobes from the Fagnano glacier, Fuego and Ewan glacier lobes (Lozano et al, ). Both seismic and ERT profiles display the Quaternary deposits affected by normal faulting related to ZFYC activity (Lozano et al, submitted).…”

“…However, the majority of these works are centred in the Atlantic coast of Tierra del Fuego (TdF) and the western zone of the Argentinean and Chilean territory. In the central area north of Lago Fagnano, studies were devoted to restricted zones including Yehuin and Chepelmut lakes (Lozano et al, , b, submitted) but presently lack a regional structural framework provided by large scale cross sections.…”