Preservation or piracy: Diagnosing low-relief, high-elevation surface formation mechanisms

Absent clear lithologic control, the presence of elevated, low-relief topography in upland landscapes has traditionally been interpreted as a signature of relative surface uplift and incision of a paleo-landscape. Such interpretations are commonly supported and quantified using analyses of river longitudinal profiles under the assumption of a static drainage network topology. Drainage networks, however, are not static, and it has been proposed recently that divide migration and drainage capture can lead to the generation of low-relief upland topography that mimics that of incised paleo-landscapes and that might be falsely interpreted as recording surface uplift and/or the onset of accelerated incision. Indeed, the interpretation of the incised southeastern Tibetan Plateau, and thus the associated geodynamic implications, have been called into question. Here we use theory and one- and two-dimensional landscape evolution models to develop a set of morphometric criteria to distinguish these alternative mechanisms of low-relief upland formation. Application to the southeastern Tibetan Plateau illustrates the utility of these metrics and demonstrates that the topography is in no way consistent with the drainage network dynamics mechanism and is fully consistent with incision into an elevated, preexisting low-relief landscape.