RESULTADOS PALEOMAGNÉTICOS PRELIMINARES EN UNIDADES IGNEAS DE LA CORDILLERA FUEGUINA, TIERRA DEL FUEGO ARGENTINA

Preliminary paleomagnetic results from seven sites located in the central Fuegian Andes, southernmost South America are presented. Sampled rocks belong to Late Jurassic basic and mesosilicatic igneous rocks cropping out in the Vinciguerra and Alvear ranges. Two sites have been recently dated in 72.0 ± 0.8 Ma and 74.7 ± 2.2 Ma (U/Pb SHRIMP). Declination anomalies have been interpreted as reflecting tectonic rotations of the sampling sites, therefore values of rotation were calculated by comparison with an Upper Cretaceous reference direction for stable South America. Significant counterclockwise rotations of similar magnitude (25o-50o) were found in all localities, except in one where deviation was only of 8o. Tectonic implications of these preliminary results are briefly discussed