A reconstruction of Apennine uplift history and the development of transverse drainages from longitudinal profile inversion

Abstract

ABSTRACT Numerous examples of transverse drainages in the Apennines inspired early, forward-thinking models to describe how rivers established and maintained their courses as mountains were being raised beneath them. We assemble the rate of base-level fall (τ-U) and associated channel χ-z data of ten transverse rivers draining the Apennine pro-wedge using a channel stream power linear inverse approach. We apply the results to evaluate competing models of transverse drainage development as well as the underlying dynamic and tectonic processes responsible for Apennine topography. The channel inversion approach employs the simplifying assumption of uniform uplift and erosion at the catchment scale, but accounts for variable rock erodibility as the first-order determinant of regional, mean channel steepness. Accordingly, local deviations in channel steepness are interpreted by the model as transient upstream-propagating waves of base-level fall originating at the catchment mouth. Modeled timing, rate, and unsteadiness of these base-level falls are broadly consistent with geomorphic, geologic, thermochronologic, and paleo-elevation isotopic data, indicating that the Apennines emerged impulsively at ~2.5 Ma at rates ranging from ~0.2–0.3 mm/yr for the central Apennines to rates of ~0.7 mm/yr for the southern Apennines. Syn-deformation and foreland-propagating superposition dominate transverse drainage development for the northern and north-central Apennines, which are underlain by an intact Adriatic slab. In contrast, further south where a slab window separates the Adriatic slab from the base of the Apennine wedge, dynamic uplift prevails and the transverse drainages have developed in response to regional superposition and integration of catchments through spillover and headwater capture processes.