Abstract

Lago Yehuin, a WNW-ESE elongated basin located in the outer fold-and-thrust belt of the Fuegian Andes, occupies a compartmented structural depression originated along a segment of the left-lateral Lago Deseado fault system. This paper describes the first geophysical survey performed within the lake. New acquired high-resolution single-channel seismic data, integrated with geological information in the surroundings of the Lago Yehuin, allowed to: (i) produce a complete bathymetric map of the lake, (ii) reconstruct the basement surface of the lake, and (iii) analyze the geometry, distribution, and thickness of the sedimentary infill. Two sub-basins were recognized within Lago Yehuin: A western sub-basin, 7.5 km long, with a maximum depth of 118 m; an eastern sub-basin, 7.2 km long with a maximum depth of 80 m. Both sub-basins are limited by a set of normal faults which overprint NE-verging thrusts. Three seismo-stratigraphic units have been identified in the seismic records: (1) a lower unit with wedged geometry interpreted as a mass flow deposits; (2) a thick (up to 120 m) intermediate unit of glacio-lacustrine nature and irregularly distributed in the Yehuin basin; (3) a thin (generally

Highlights

  • Lago Yehuin (LY) is located in the southernmost Andes, in isla Grande de Tierra del Fuego (Fig. 1)

  • The contribution of this work is mainly focused in the analysis of newly acquired seismic data within the LY, a previously unexplored area from a geophysical point of view, located in the core of the isla Grande de Tierra del Fuego

  • The seismic records have been used to image the sub-bottom morphology of the basin, to derive its sedimentary architecture, and to propose an evolutionary history of the lake within the general tectonic framework of the external Magallanes fold-and-thrust belt

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Summary

Introduction

Lago Yehuin (LY) is located in the southernmost Andes, in isla Grande de Tierra del Fuego (Fig. 1). LY is a lacustrine basin located 10 km north of lago Fagnano, the largest freshwater lake of Tierra del Fuego, which occupies a pull-apart basin developed within the South America-Scotia transform boundary (Fuenzalida, 1972; Dalziel, 1989; Lodolo et al, 2003). LY, which displays a WNW-ESE oriented elongated shape, lays in a low altitude zone (between 900 and 50 m a.s.l.) and is part of a provincial reserve named “Corazón de la Isla”. The lake is the largest freshwater lacustrine body within the reserve, and the largest basin within the Fuegian steppe, with a surface of 43 km.

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