Geophysical methods applied to Quaternary studies in glacial environments: Río Valdez outcrop, Tierra del Fuego, Argentina

Abstract

In the Río Valdez mouth, located in the southeastern coast of Fagnano lake, Tierra del Fuego, an outcrop of 7 m thick lacustrine sediments was identified. Taking into account geomorphological and sedimentological surveys, such outcrop was interpreted as a rhythmic glacio-lacustrine deposit, formed in a frontal morainic complex during the Pleistocene. Ground magnetic and resistivity surveys were carried out, trying to determine the thickness and areal extension of these lacustrine sediments. A maximum E-W extension of ~220 m and a minimum NNW-SSE one of ~180 m were determined. A minimum thickness of ~20 m was estimated. Taking into account this thickness and an assumed average sedimentation rate, the natural dam that promoted the paleolake and their related lacustrine sediments could have existed previously to MIS 2, when the Last Glacial Maximum took place in the region. The applied geophysical methods proved to be a powerful tool for the investigation of palaeo-lake deposits.