A New Paleomagnetic Study of the Itararé Group from the State of São Paulo, SE Brazil and Implications for Pangea Reconstructions: Inclination Shallowing or Pervasive Remagnetizations?

Abstract:

When reconstructing the paleogeography of Pangea, paleomagnetic data for the Permo-Carboniferous impose an overlap between the two major continental blocks, Laurasia and Gondwana, in the traditional Pangea-A assemblage, leading to the alternative Pangea-B model. However, the Permo-Carboniferous apparent polar wander path (APWP) of South America, for which the overlap is the most severe, is dominated by sedimentary rocks and the few igneous rocks are either remagnetized or have suffered from tectonic rotations. Bilardello and Kodama (2010) have shown how inclination shallowing corrections of Gondwana sedimentary rocks may completely eliminate the continental overlap between the northern and southern continental blocks. Such blanket inclination corrections performed using a fixed flattening factor, however, lack a solid base because inclination shallowing is lithology-specific, depending on clay content, magnetic carrier, particle size and shape among other factors, and should not be performed systematically. New paleomagnetic data from the Permo-Carboniferous Itararé Group of Brazil reveal extensive remagnetizations in these rocks, as do recently published studies that also highlight pervasive South American remagnetizations which affect some of the paleopoles that define the Permo-Carboniferous portion of South American APWP. We present new paleomagnetic, rock-magnetic and anisotropy data from the Brazilian Itararé Group and also point out flaws in the widely used and inclination corrected South American Permo-Carboniferous APWP reported in Torsvik et al. (2012). All this evidence informs us that the Pangea controversy is still far from reconciled.