Indicadores geofísicos sobre la localización del límite entre las placas Sud America-Scotia en Tierra del Fuego (Argentina)

TASSONE A.; LODOLO E.; LIPPAI, H.;; ZANOLLA, C.; HORMAECHEA, J. L.; COREN, F.; VIDMAR, R.; RINALDI, C.

XIV Congreso Geológico Argentino

Congreso; XIV Congreso Geológico Argentino; 1999

Asociación Geológica Argentina (AGA)

Geophysical constraints for the Scotia-South America píate boundary location in the Tierra del Fuego región. The geológica! structure of the tectonic boundary between the South America and Scotia plates in the Tierra del Fuego región has been investigated during two geophysical and geologícal campaigns carried out in February-March, and October-November 1998. 364 DGPS-fixed magnetic and gravimetric data points have been recorded in the central part of the island and along its eastern coast, and petrologic and geologic data have been collected on the most significant outcrops. A system of east-west-trending asymmetric folds and associated thrusts, affected by later N-S trending faults have been recognized along the Atlantic coast of the island, where the main lithologic formations are exposed. Scarce outcrops are present in the central part of the island, apart along the main road connecting Rio Grande and Ushuaia, and along the northern shore of the Lago Fagnano, where the presence of a major tectonic lineament, in correspondence of vvhich the affected rocks are strongly brecciated, has been inferred. Analyses of Synthetic Aperture Radar (SAR) images have confirmed the presence of east-west-trending morphological alignments, which can be associated with this main tectonic lineament. It presents a gravimetric expression on the free-air gravity map, where at least three parallel-oriented gravimetric minima have been recognized. 1 satellite-derived free-air gravity anomaly map seen in ¡ Atlantic Ocean off the Tierra del Fuego coast clea represents the eastward prosecution of this structure. localized susceptibility contrast found to the south-east of in Lago Fagnano, indicates the presence of an igneous body the subsurface intruded in Cretaceous shales-mudston which can be related to the development of the southí Andean magmatic are, or to a later event. The acquired data combined with geometrical extrapolations and topographic evidences, strongly suggest that the major lineament infered along the Lago Fagnano form part of the sinistral strike-s Magallanes fault system known in literature, which is in onshore location of the South America-Scotia plate bound: in the Tierra del Fuego región.