Origin and evolution of lago Yehuin (Tierra del Fuego, Argentina): Results from a geophysical survey

Jorge G Lozano,Donaldo M Bran,María E Cerredo,Alejandro Tassone,Emanuele Lodolo,Luca Baradello,Marco Menichetti,Juan F Vilas,Juan P Ormazabal,Federico Esteban

doi:10.5027/andgeov45n3-3085

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

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.

Objectives

Discussion

Conclusion