A new Jurassic-Recent apparent polar wander path for South America and a review of central Andean tectonic models

The Jurassic to Recent palaeomagnetic data from the stable cratonic areas of South America and Africa are reviewed and evaluated. From the combined data set seven mean reference pole positions are calculated for the Early, Middle and Late Jurassic, Early and Late Cretaceous, Palaeogene and Neogene. Most of these new palaeopoles are well defined and indicate a complex course of apparent polar wander for the South American plate. Comparison of the palaeomagnetic data from the Andean margin with the reference poles indicates vertical axis rotations defining a broad pattern of anticlockwise rotations north of the Arica Deflection at approximately 19 degrees S, and clockwise rotations to the south. Further analysis indicates, however, that the distribution and magnitude of rotations is more complicated than this broad division. Tectonic models proposed to explain the pattern of rotations, and the possible origins of the Arica Deflection, are discussed. It is suggested that the rotations probably result from localised in situ rotations controlled by strike-slip fault systems or thrust sheets rather than large-scale rotation mechanisms. The broad rotation pattern may result from the influence of pre-existing structures in the margin or variations in the flexural rigidity of the Brazilian Shield behind the deformation zone. (C) 1998 Elsevier Science B.V. All rights reserved.