Drainage-divide migration, controlled by rock-uplift and rainfall patterns, may play a major role in the geomorphic evolution of mountain ranges. However, divide-migration rates over geologic timescales have only been estimated by theoretical studies and remain empirically poorly constrained. Geomorphological evidence suggests that the Sierra de Aconquija, on the eastern side of the southern Central Andes, northwest Argentina, is undergoing active westward drainage-divide migration. The mountain range has been subjected to steep rock trajectories and pronounced orographic rainfall for the last several million years, presenting an ideal setting for using low-temperature thermochronometric data to explore its topographic evolution. We perform three-dimensional thermal-kinematic modeling of previously published thermochronometric data spanning the windward and leeward sides of the range to explore the most likely structural and topographic evolution of the range. We find that the data can be explained by scenarios involving drainage-divide migration alone, or by scenarios that also involve changes in the structures that have accommodated deformation through time. By combining new 10Be-derived catchment-average denudation rates with geomorphic constraints on probable fault activity, we conclude that the evolution of the range was likely dominated by west-vergent faulting on a high-angle reverse fault underlying the range, together with westward drainage-divide migration at a rate of several km per million years. Our findings place new constraints on the magnitudes and rates of drainage-divide migration in real landscapes, quantify the effects of orographic rainfall and erosion on the topographic evolution of a mountain range, and highlight the importance of considering drainage-divide migration when interpreting thermochronometer age patterns.
Bibliographical noteFunding Information:
T.S. acknowledges support from the Helmholtz W2/W3 Professorinnen Program ( W2_W3-0072 ). P.v.d.B. and M.D. were supported by fellowships from the Alexander von Humboldt Foundation , and M.D. also by an Early Career Research grant from the British Society for Geomorphology that supported sample collection. E.O. was supported by the Deutsche Forschungsgemeinschaft (DFG) and the Federal State of Brandenburg within the International Research Training Group IGK2018 “SuRfAce processes, TEctonics and Georesources: The Andean foreland basin of Argentina” (STRATEGy DFG 373/34-1 ). We thank W. Düsing for help with sample collection and processing. The Deutsches Zentrum für Luft- und Raumfahrt (DLR) provided TanDEM-X digital elevation data through grant DEM_GEOL1915 awarded to T.S. and M.D. We are grateful to two anonymous reviewers whose detailed comments helped us to improve the clarity and presentation of our work.
© 2021 Elsevier B.V.
- Central Andes
- cosmogenic nuclides
- drainage-divide migration
- landscape evolution
- orographic rainfall