The timing of large drainage rearrangement in South America: A study based on morphological and ecological evidence

This study aims to characterize and determine the timing of a major drainage rearrangement between two vast river basins, each exceeding 600,000 km²: the Paraná and São Francisco basins in South America. We used geomorphological analyses and the computational Black Top Hat (BTH) method to identify river captures. By using freshwater fish distribution and evolution data, we performer biogeographical analyses to assess the fish dispersal patterns. Our results show that in the past the upper Paraná River (known locally as the Grande River) once flowed into what is now the São Francisco River Basin. Biogeographical analysis corroborates this past connection between Grande and São Fracisco rivers This analysis reveals also that between 6 and 5 and 2 million years ago, a significant drainage rearrangement occurred, when the Paraná River Basin captured the Grande River and its tributary (the Sapucaí River). In this process the São Francisco Basin losing 50,000 km² of its area to the Paraná River Basin.