Estudio Paleomagnético de Rocas Sedimentarias Terciarias de la Puna Salteña: determinación de rotaciones horarias.

PREZZI, CLAUDIA BEATRIZ; VILAS, JUAN; SINITO, ANA MARIA

Revista de la Asociación Geológica Argentina

Asociación Geológica Argentina

Año: 1996 vol. 51 p. 261 - 273

0004-4822

On the Argentine Puna two phases of deformation, Late Tertiary and Quaternary, are recognized. Studies of Nazca-South American plate motions indicate convergence towards 77° ± 12° since 10 Ma. Although Tertiary shortening is not parallel to this direction, Quaternary shortening coincides with it. This situation could be explained by: a) the stress causing the faults changed direction during the Late Cenozoic, or b) the zone containing the older faults was rotated about a vertical axis. Isacks´s model for the Bolivian orocline predicts a clockwise regional rotation for the southern limb. Although the model is probably oversimplified, it provides a testable hypothesis. A palaeomagnetic study, to determine regional or local vertical axis rotations was carried out between 24° 30 S and 24° 40 S and 67° 00 and 67° 15 O. Different demagnetization techniques were applied. Most specimens show a multicomponent behaviour, although it was possible to isolate pretectonic primary remanent magnetizations that indicate clockwise rotations of approximately 10-15° of magnitude.