|Authors||S. Hippchen, B. Ghorbal, C. Moder and S. Clark|
|Title||Revisited Block Boundaries in South America - a Study of Intraplate Deformation|
|Afilliation||Scientific Computing, Scientific Computing, Scientific Computing|
|Year of Publication||2013|
|Secondary Title||European Geosciences Union General Assembly 2013|
In plate reconstruction modeling we rely mostly on magnetic lineations on the seafloor to constrain our models in time and to deduce the velocities at which the plates move. These lineations occur due to the reversal of the Earth's magnetic field and are recorded during the opening of a mid ocean ridge. However, the reliability of this approach becomes limited during a period where no magnetic reversal has been recorded. One of these periods is the Cretaceous Superchron, an almost 40 Ma era with no recorded magnetic reversal. Particularly for reconstructing the opening of the South Atlantic this era poses a problem, since it took place between ca. 120 and 83 Ma, a time when rifting between South America and Africa had just begun. Most existing plate models are predominantly based on geometrical constraints in order to achieve the best-opening fit, which leads to intraplate deformation in South America accommodated very differently from model to model. We choose, in addition to the classical approach, to use strong geological and geophysical constrains to better define zones of intraplate deformation and hence the most viable block boundaries. This work consists of three parts: First, we compare the various existing plate reconstruction models, with focus on where and how much intraplate deformation is accommodated within South America. In a second step we study available data like gravity, crustal thickness, geology, major faults zones, basement age and changes of the dip angle of the downgoing slab of the Peru/Chile trench to investigate current tectonics and strain distribution. Based on this analysis we postulate an updated block geometry for South America. In a third step, we reconstruct the opening of the South Atlantic using the updated block model and rotation file for South America. We analyze the result by comparing it to the pre-opening fit of the existing plate models.