Morpho-Bathymetric survey of Lago Roca (Tierra del Fuego).

LODOLO E.; TASSONE A.; BARADELLO, L; LIPPAI, H,; GROSSI, M.

BOLLETTINO DI GEOFISICA TEORICA ED APPLICATA

ISTITUTO NAZIONALE DI OCEANOGRAFIA E DI GEOFISICA

Lugar: Trieste; Año: 2010 vol. 51 p. 125 - 126

0006-6729

Lago Roca occupies a secondary tectonic lineament pertaining to the main Beagle Channel fault system (Tassone et al., 2005). It is located within the Lapataia Natural Park, 25 km to the west of the city of Ushuaia (Fig. 1). The lake, trending broadly NW-SE, is about 10.5-km-long, with average width of about 0.7 km. In order to analyze the main morphological and shallow structural setting of this basin, an extensive high-resolution seismic survey was carried out on November 2009, in the frame of an Italian-Argentinean cooperative research study funded by the Italian Foreign Ministry. These data have permitted to derive for the first time a bathymetric map of the lake (through the conversion of seismic arrival times in water depths), and image morphologies and depositional architecture of the glacial and glacio-lacustrine deposits filling the basin. These information, combined with analysis of structural and geomorphological features of the surrounding areas, will aid to reconstruct the Roca basin origin and identify the Late Quaternary inter-glacial episodes responsible of the deposition of the sedimentary sequences. The glacial activity, in combination with the sea level variations and tectonic activity, has played an important role in shaping the morphology of the Lago Roca basin. In fact, the area lies at the foot of the Cordillera Darwin, where a large ice-sheet is still present above the higher peaks of this mountain chain (Gordillo et al., 1993). Morphological and sedimentological evidence, mostly represented by raised beaches and deposits rich in marine organisms, testify that the northern coast of the Beagle Channel has undergone a general drop of the sea level during Holocene (Rabassa et al., 1986). This progressive marine regression has modified the coastal landscape of the area and in some cases has severely changed the morphological environment of the surrounding areas (Borromei and Quattrocchio, 2007). Moreover, the general morphology of Lago Roca is clearly controlled by the tectonic activity along the Beagle Channel fault system and its geometry most probably reflects its sub-bottom structure.