Evaluation of the Flexural Influence of the Andean Cordillera on the Pantanal Basin: Results From Visco-Elastic Numerical Models.

In the last two decades, previous works explored the flexural influence of the formation of the Andean Cordillera on the development of intracontinental basins, like Pantanal Basin, based on the formulation of thin elastic plates. In the present work we assess how the load of the Andean Cordillera flexurally affected the South American plate using a finite element model with a visco-elastic rheology to simulate the deformation of the continental lithosphere over time under different geotectonic conditions. The scenarios simulate the evolution of an orogen of geometry similar to the Andes at latitude 18.5°S over 40 million years. During the numerical experiments, the distance between the forebulge and the center of the orogen was calculated through time and the results were compared with geological constraints. Scenarios with different lithospheric thickness, from 70 to 200 km, were tested to evaluate its influence on the evolution of the interior basins. The distances obtained between the forebulge and the orogen for the different scenarios show that they do not reach the region of the Pantanal Basin, except for the scenario with a lithosphere 200 km thick, in which the geometry of the predicted foredeep adjacent to the cordillera does not agree with the geological and geophysical observations. These results indicate that it is unlikely that the rising of the Andes flexurally influenced the formation of the Pantanal Basin. Based on the present results, the basin should be geographically located at the backbulge region, but its amplitude is not enough to cause the observed subsidence in the Pantanal Basin. Therefore, another mechanism, e.g. dynamic topography, must have been responsible for the Pantanal subsidence.