Basement geometry of Lago Fagnano

FEDERICO, ESTEBAN; TASSONE, ALEJANDRO; LOLODO, EMANUELE; MENICHETTI, MARCO; LIPPAI, HORACIO; DARBO, ALEXIA; BARADELLO, UCA; VILAS, JUAN F.

Antofagasta - Chile

Congreso; XIII Congreso Geológico Chileno; 2012

Universidad Católica

Abstract. Lago Fagnano, an E-W elongated basin located in the central part of Isla Grande de Tierra del Fuego, occupies a structural depression originated along a segment of the Magallanes-Fagnano fault system. Its evolution was mostly conditioned by tectonic process, and later was affected by glacial and glacio-lacustrine depositional events. New high-resolution single-channel seismic data, integrated with published seismic profiles and geological information acquired in the surroundings of the Lago Fagnano, allows us to reconstruct the basement surface of the lake, and the geometry and thickness of glacial and glacio-lacustrine sequences. 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-Fagnano fault system, along with the distribution, geometry, and thickness of the sedimentary units, show that the general morphology of the Lago Fagnano was mostly controlled by pre-existing tectonic features.