Tectonic implications of post-folding permian magnetizations, Carapacha basin Argentina

RENATA N TOMEZZOLI1,2, RICARDO N MELCHOR1,3, WILLIAM D MACDONALD4

Earth, Planets and Space

TERRA SCIENTIFIC PUBL CO

Lugar: Japon; Año: 2006 p. 1235 - 1246

1880-5981

Paleomagnetic results from Permian clastic and igneous rocks of the Carapacha Basin of the Gondwanides orogenic zone of central Argentina are mainly consistent with results reported previously from the same zone further east, e.g., in the Sierra de la Ventana. Three lithologic entities were analysed: the lower member (Calencó) and upper member (Urre-Lauquen) of the Carapacha Formation, and an andesite (El Centinela Formation) intrusive into the upper member. The directions of their characteristic remanences are similar, differ significantly from the present field direction, and are post-tectonic. The in situ magnetization directions are moreover consistent with directions expected for late Permian poles of the APWP for South America. The in situ pole for the lower Carapacha Formation is 70ºS, 049ºE, A95 = 11º (Calencó pole); the pole for the upper Carapacha, combined with similar directions from the intrusive El Centinela andesite, is 64ºS, 005ºE, A95 = 5º (Curacó pole). These magnetizations imply that the Carapacha Formation, with a minimum age of early Late Permian (about 260 Ma.), was deformed before the end of the Permian. Structural evidence, as well as palaeomagnetic, IRM, and AMS experimental results, support the interpretations.