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Earth Planets Space, Vol. 58 (No. 10), pp. 1235-1246, 2006

Tectonic implications of post-folding Permian magnetizations in the Carapacha Basin, La Pampa province, Argentina

Renata N. Tomezzoli1,2, Ricardo N. Melchor1,3, and William D. MacDonald4

1CONICET—Consejo Nacional de Investigaciones Científicas y Técnicas
2Universidad de Buenos Aires, F.C.E. y N., Departamento de Ciencias Geológicas, Pab. II., Ciudad Universitaria. C1428EHA, CABA, Argentina
3Universidad Nacional de La Pampa, Av. Uruguay 151, 6300 Santa Rosa. La Pampa, Argentina
4State University of New York, Binghamton, NY 13902-6000, USA

(Received February 9, 2006; Revised June 5, 2006; Accepted June 6, 2006; Online published November 8, 2006)

Abstract: Paleomagnetic results from Permian clastic and igneous rocks of the Carapacha Basin of the Gondwáides 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 and upper member of the Carapacha Formation, and an andesite intrusive into the upper member. The directions of their characteristic remanences are similar, differ significantly from the present field direction, and are post-folding. 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 70°S, 049°E, A95=11° (San Roberto pole); the pole for the upper Carapacha, combined with similar directions from the intrusive, is 64°S, 005°E, A95=5° (R÷o Curací 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 paleomagnetic, IRM, and AMS experimental results, support the interpretations. The paleogeographic implications of these results are interpreted as a significant counterclockwise movement of Gondwana between the early and the late Permian.
Key words: Gondwana, Carapacha Basin, South America, Late Paleozoic, paleomagnetism, magnetic anisotropy, AMS.


Corresponding author E-mail: renata@gl.fcen.uba.ar


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