Seismic study of the Southernmost Andes. The contact between Scotia and South American Plates.

TASSONE, A.; COMINGUEZ, A.; YAGUPSKY, D.L.; ALVARADO, P.; LODOLO, E.; MENICHETTI, M.

San Francisco. USA

Otro; American Geophysical Union (AGU) Fall Meeting; 2003

The relationships between the sinistral Magallanes-Fagnano continental transform fault (MFS), a major segment of the boundary between Scotia- Southamerican.plates, and the northern flank of the western Scotia Sea, characterized mostly by compressional structures, have not been yet clearly identified. From data processing, depth seismic-migration modeling and interpretation of 800 km of seismic reflection profiles, this study presents one morpho-structural analysis of these two main tectonic elements. In the offshore part of the Malvinas fold-and-thrust belt, five main seismic units have been recognized. Steeply dipping (mainly to the south) reverse faults cut through the folds. Some of these faults represent old extensional faults of the Middle-Mesozoic Rocas Verdes marginal basin rifting, which have been subsequently inverted by compressional stress fields. A noticeable fault system is recognized in the seismic profile, which involves both the sedimentary cover and the acoustic basement. This fault is interpreted as the result of shear stresses produced along the transcurrent South America-Scotia plate boundary. In the SW border of Malvinas Basin, four major discontinuities were recognized. Each discontinuity represents important changes in the regional geodynamic evolution: Early-Late Jurassic rift; Thermal subsidence (Late Jurassic-Late Cretaceous); Transitional stage, to foreland basin (Late Cretaceous-Eocene) and Foreland (since Eocene).