The influence of Dynamic Topography on the Sedimentary Evolution in the Amazon Fan and Interior Basins in Northern South America.

The formation and evolution of the present transcontinental Amazon river, the largest drainage system on Earth, is a result of the combined effect of different geodynamic processes. The Andean uplift and the increase in surface denudation along the cordillera affected the stratigraphic evolution of interior and marginal sedimentary basins in northern South America. Concomitantly, variations in the subduction angle of the Nazca plate under the continental lithosphere during the Miocene also contributed to create dynamic topography that perturbed the surface and modified the drainage pattern through time. In the present work we conducted a series of numerical experiments combining erosion, sedimentation, Andean orogeny, flexural isostasy and dynamic topography to analyze the paleogeographic evolution of northern South America during the last 40 million years. We conclude that the formation of the present drainage system in Amazonia was mainly guided by the asymmetric influx of sediments to the interior of the continent and marginal sedimentary basins induced by the Andean orogeny, while the dynamic topography modulated the timing and amplitude of the accommodation space generation and the consequent stratigraphic evolution in the Solimões, Amazonas, Marajó, and Foz do Amazonas sedimentary basins.