Bidirectional Migration of Major Drainage Divides in Tectonically Stable Continental Plateaus

This study investigates the dynamics of major drainage divides in continental plateaus characterized by low tectonic activity and gentle relief. Using remote sensing, field observations, and integrated morphometric analyses (χ and ksn indices and knickpoint distribution), we examine the behavior of the drainage divide along the boundary between the Tocantins and Paraná river basins in the Central Plateau of South America. The study area presents a divide that is barely perceptible in the landscape and exhibits multiple geomorphological anomalies, including elbows of capture, lowered divides and dry channels. These features suggest that, in the past, the Paraná River Basin expanded at the expense of the Tocantins River Basin. However, morphometric analyses indicate that, at present, the Tocantins River Basin tends to advance over the Paraná River Basin. The regional divide is therefore not static but is undergoing dynamic reorganization, with different segments advancing or retreating between adjacent basins. These observations support the interpretation of this divide as bidirectional, meaning that the direction of divide migration varies through time and space, something theoretically predicted but rarely documented in major drainage divides. Finally, the results highlight the importance of integrating morphometric metrics with geomorphological field evidence, particularly in tectonically stable continental plateaus.