Singlechannel Seismic Survey in Lago Fagnano, Tierra del Fuego.

ESTEBAN, F.D.; TASSONE, A.; LODOLO, E.; MENICHETTI, M.; LIPPAI, H.; DARBO, A.; GROSSI, M.; BARADELLO, L.

Buenos Aires

Workshop; XIV Giambiagi Winter School; 2012

Departamento de Física, Facultad de Ciencias Exactas y Naturales, UBA

Lago Fagnano (LF), an E-W elongated basin located in Tierra del Fuego, occupiesa structural depression originated along a segment of the Magallanes-Fagnano faultsystem. Its evolution was mostly conditioned by tectonic process, and later was affected by glacial and glacio-lacustrine depositional events. In order to study the lake?s origin we reconstructed the basement surface, and the geometry and thickness of glacial and glaciolacustrine sequences. For this, three seismic stratigraphic units were interpreted from the profiles: (1) a bedrock/basement complex, (2) an ice-contact/glacial deposits, and (3) a glacio-lacustrine and lacustrine successions. To convert the two-way travel time of the high resolution profiles in depths, a water sound velocity of 1432 m/s was used. For the lacustrine, fluvial and glacial sediments a sound velocity of 1500 m/s. The seismostratigraphic units were then correlated with the geologic units outcropping around the LF. Horizon?s grids were created with a point Kriging method and with a forcing factor along the E-W direction, given the peculiar geometry of LF. We recognized three main sub-basins within the Lago Fagnano: (1) a medium-size (ca. 21 x 5 km), deep (373 m), and asymmetrical basin to the east; (2) an E-W trending (44 x 3 km), shallower (150 m) central sub-basin; and (3) a smaller (3.5 x 1.3 km), shallow (128 m) sub-basin to the west. The shape of the sub-basins and their location in relation with the Magallanes-Fagnanofault system, along with the distribution, geometry, and thickness of the sedimentary units, show that the general morphology of the LF was mostly controlled by pre-existing tectonic features.