Pre-Andean Rotations in NW Argentina: a Clue to a Possible Tectonic Model?

SPAGNUOLO, CECILIA M.; RAPALINI, AUGUSTO E.; ASTINI, RICARDO A.

Fort Lauderdale, USA

Congreso; American Geophysical Joint Assembly,; 2008

American Geophysical Union

AN: GP44A-07TI: Pre-Andean Rotations in NW Argentina: a Clue to a Possible Tectonic Model?AU: * Spagnuolo, C MEM: cspagnuolo@gl.fcen.uba.arAF: Universidad de Buenos Aires, INGEODAV Depto. Cs. Geologicas Universidad de Buenos Aires Pabellón 2, Ciudad Universitaria, Buenos Aires, C1428EHA, Argentina AU: Rapalini, A EEM: rapalini@gl.fcen.uba.arAF: Universidad de Buenos Aires, INGEODAV Depto. Cs. Geologicas Universidad de Buenos Aires Pabellón 2, Ciudad Universitaria, Buenos Aires, C1428EHA, Argentina AU: Astini, R AEM: raastini@efn.uncor.eduAF: Universidad Nacional de Córdoba, Depto.Cs.Geológicas, Universidad Nacional de Córdoba, Argentina, Argentina AB: In the early Paleozoic western South America underwent a complex tectonic history that includes a more or less continuous active margin that witnessed the accretion and displacement of several terranes. In particular, many models have been proposed to account for the geologic evolution of the northwestern region of Argentina in the Lower Paleozoic, which range from a wholly ensialic evolution to the accretion of exotic and/or para- autochthonous terranes. During the last three years a systematic paleomagnetic study on Lower Paleozoic sedimentary and volcanic rocks from NW Argentina have yielded a Late Cambrian paleomagnetic pole for the Eastern Cordillera (23° S 65° W, Campanario Fm.), an Early to Middle Ordovician pole for the Famatina volcanic arc (28° S 68° W, Cerro Morado and Los Molles Fms.) and a Permian one in the same locality. A clockwise rotation around 35° is found for both Lower Paleozoic units, while the Permian one is coincident with the apparent polar wander path of Gondwana. The Early Paleozoic results are virtually identical to others found several years ago in the Eastern Puna magmatic belt and in the same Famatina System. On the other hand, a counter-clockwise rotation has been reported for Early Paleozoic rocks exposed at different localities of the Antofalla block. Those results are reviewed together with the structural and geological information of the region in order to evaluate the feasibility of different tectonic models such as i) the opening and closure of a back-arc basin, ii) the collision or displacement of a para-autochthonous terrane, or iii) the development of systematic block rotations associated to oblique subduction or scape tectonics. DE: 1527 Paleomagnetism applied to geologic processesSC: Geomagnetism and Paleomagnetism [GP]MN: 2008 Joint Assembly