CONICET | Buscador de Institutos y Recursos Humanos

Global paleogeographic models for the Paleoproterozoic are largely uncertain despite significant progress in the last two decades. Paleomagnetic data for that era is scarce, uneven and of varied reliability for most cratons. Recently published paleomagnetic results from some post-tectonic plutons in the Piedra Alta terrane (Uruguay) suggested that the Río de la Plata craton experienced a fast apparent polar wander at very high latitudes between ca. 2.1-2.0 Ga. We present new paleomagnetic results from nine small plutonic bodies not previously sampled in the same terrane. After standard paleomagnetic techniques, complemented with rock-magnetic studies, petrographic analysis and magnetic fabric investigations, three new paleomagnetic poles were computed from the Cufré-Cerro Albornoz grantic plutons, the Carreta Quemada gabbro and the Tia Josefa tonalite, respectively. These new poles fall along the recently presented apparent polar wander track for the Rio de la Plata craton confirming high latitude positions for this block and fast polar displacement. A sequence of sixpoles along the track is determined, from oldest to youngest, by the Mahoma-Marincho, Carreta Quemada, Cufré-Cerro Albornoz, Isla Mala, Tía Josefa and Soca plutonic bodies. A coherence is also observed in the polarity of remanence along the track, showing dual polarity remanence for the older poles (Mahoma-Marincho and Carreta Quemada), normal polarity (assuming southern hemisphere location of the craton) for Cufré-Cerro Albornoz and reverse polarity for the Isla Mala, Tía Josefa and Soca intrusives. These new data also confirm that the hypothetical Paleoproterozoic Atlantica continent, encompassing several South American and African cratons, either never existed or had a radically different paleogeographic configuration.