A COMPREHENSIVE PALEOMAGNETIC STUDY FO THE ITARARE' GROUP FROM THE STATE OF SAO PAULO, BRAZIL, IN THE CONTEXT OF PANGEA RECONSTRUCTIONS: EVIDENCE FOR PERVASIVE SOUTH AMERICAN REMAGNETIZATIONS
We performed an extensive paleomagnetic study, including rock-magnetic characterization and anisotropy, of the Permo-Carboniferous Itararé Group throughout the state of São Paulo, Brazil. This also includes three basalt sills that intruded the sedimentary rocks, most likely during the post-Jurassic breakup of Pangea. We obtained a wealth of paleomagnetic directions that are suspiciously consistent with the directions isolated from the basalts, whereas a limited number of sites appear independent of the volcanic rocks. These independent sites allowed us to calculate a paleopole that we believe to be primary Upper Carboniferous, and which has been corrected for inclination shallowing using the anisotropy of magnetic remanence.
However, rock-magnetic evidence, a fold test, and shape analysis of the distributions of directions and poles obtained from the bulk of the Itararé sites provides convincing evidence for these magnetizations to be secondary. A comparison of these paleopoles and data presented in the literature not only supports the notion that these rocks were remagnetized during the Cretaceous, but also suggests that many published Permo-Carboniferous poles throughout South America are affected by these secondary magnetizations.
Scrupulous revision of the Permo-Carboniferous Apparent Polar Wander path for South America, and elimination of all poles suspected to be remagnetized, yields a new path that is consistent with a Pangea-A assemblage, without the need to apply systematic blanket inclination shallowing corrections that are unjustified and scientifically unsound.