KNICKZONE MIGRATION IN FOLD-THRUST BELTS: A CASE OF STUDY FROM THE CENTRAL SECTOR OF THE MEXICAN FOLD-AND-THRUST BELT (CENTRAL MEXICO)

Several studies around the world have demonstrated that knickzones migrate upstream where there is a drop in the base-level of rivers. Rates of knickpoint recession largely depend on the catchment area which is a proxy of stream discharge. However, evaluating how a river profile is forced in compressional settings has received less attention. Here we study the case of knickzone migration in a shortening setting where at least three main deformation pulses starting in the Late Cretaceous and ending in the Paleogene have conditioned the local landscape evolution. These events have produced three zones of folds and thrust faults. We analyzed the longitudinal profiles of Moctezuma and Extoraz rivers which incise across the Mexican Fold–Thrust Belt (MFTB), that is located in central Mexico, to evaluate how rivers respond to the deformation imposed by folding and thrusting. On the river profiles we detected several knickzones close to the zones of folds and thrust faults. Further analysis at each shortening zone, reveals that the distance upstream from folds and thrust fault to their knickzone has a good correlation with drainage area (R² = 0.60 for folds and R² = 0.59 for thrust faults). Our results strongly suggest that in the MFTB rivers are forced by the style of deformation resulting in the migration of knickzones. We propose that the evidence of knickzone migration along the Moctezuma and Extoraz rivers is also indicative of a reactivation of the MFTB by the low angle subduction of the Cocos plate beneath the North American Plate.