Confined alluvial basins as evidence of recent tectonic conditioning of the drainage in the Northwestern Minas Gerais State, Brazil

Resumo

This study investigated how alluvial sedimentation areas and compressed meanders in the confined basins of northwestern Minas Gerais State serve as evidence of recent tectonic restructuring. This was achieved by employing a morphotectonic approach that considers the sensitivity of river channels to small vertical and horizontal crustal variations. For this purpose, the drainage of the Paracatu and Urucuia River catchments at a scale of 1:100,000 was ordered, and images from the Google Earth Platform and numerical models of hypsometry, shaded relief, and slope were used to support visual inspections and the delimitation of confined basins. By applying morphometric and geomorphic indices, the shape and sedimentation patterns were assessed separately and comparatively in sections of fourth (or higher)-order channels that were considered anomalous. Moreover, a new methodological approach was proposed to quantitatively describe the channel dynamics within these basins. The indices showed correlations between confined basins, regional structural directions, and evidence of recent tectonic reactivation, as suggested by channel entrenchment and compressed meander sections. This study revealed that sediment accumulation occurred in specific sections. This accumulation is correlated with subsiding areas and the imposition of thresholds along channels, which are strongly linked to recent and low-intensity tectonic activity.