Velocidades sísmicas de las unidades aflorantes en el flanco occidental de la Sierra de La Invernada, Precordillera de San Juan

PÉREZ LUJÁN, S.B.; ALVARADO, P.; GÜELL, A.; SÁEZ, M.; VUJOVICH, G.I.

Revista de la Asociación Geológica Argentina

Asociación Geológica Argentina

Año: 2013 vol. 70 p. 173 - 182

0004-4822

Seismic velocities in outcropping units in the western flank of the la Invernada range, San Juan Precordillera.P-wave seismic velocity (Vp) determinations are shown in this work for a region in the western flank (Don Carmelo nature reserve) of the la Invernada range in the Ullúm Department of the San Juan Province. The velocities obtained using the seismicrefraction method indicate Vp values of 550; 1.670 and 4.134 m/s and thicknesses of 1 m and 7 m approximately, for a two-layer over a higher Vp half space model. The exposed units show greywacke and well compacted sandstones, which have a good correlation with the deepest and higher Vp values of the seismic model. Also the lowest Vp values are consistent with alluvial material located in the shallower seismic layers (< 7m depth). Other units observed on the surface exhibit outcrops of diabases and gabros, which were not geophysically explored. However, a comparison between the observed lithologies and Vpvalues with a global database predicts the continuation at depth of mafic rocks associated with even higher Vp values than those determined at the surface. These results are of interest because they help us to identify an ophiolite belt in the Precordillera, aregion presently characterized by an overthickened crust of 64 km.Keywords: seismic refraction, basement, P waves, ophiolite, Precodillera, petrology, geophysics.