How erosional efficiency modulates landscape response to drainage reorganization: New empirical evidence from the Andes

The fluvial network in active mountain ranges is considered to evolve from longitudinal to transverse-dominated drainage systems. This hypothesis links to the forelandward migration of the orogen, while crustal thickening modifies the range's flank slopes, enhancing erosional efficiency. We probe such a proposition with new empirical observations from the Colombian Andes by studying the recent capture of the longitudinal Su ' arez and Chicamocha Rivers by the transverse Sogamoso River. Firstly, by integrating published low-temperature ther-mochronology and quantitative topographic metrics like chi, we found that rejuvenated rock uplift in the Cocuy and Yariguies ranges delays the transition from longitudinal to transverse-dominated drainage systems by compensating the across-divide contrasts in erosion. To further constrain the spatiotemporal response of the Su ' arez and Chicamocha Rivers after the discrete capture, we computed sediment-gauge erosion rates in conjunction with rainfall-normalized channel steepness and Gilbert metrics. We observe stark contrasts in erosion rates between the Chicamocha (maximum of 148.22 +/- 44.86 m/Myr) and Su ' arez Rivers (maximum of 71.9 +/- 21.5 m/Myr). Higher erosion rates in the former are expressed with widely distributed slope-break knickpoints that migrated further upstream with catchment expansion at the expense of the less efficiently erosive Su ' arez River basin. We interpret these erosional differences as a lithological control on the pace of topographic response to an external perturbation (discrete capture), given low-lying sedimentary rocks delay the erosional response of the Su ' arez River basin. Our research therefore emphasizes the role that lithology poses in keeping the landscape in an unsteady topographic condition.