The evolution of hydrography in the retro-wedge side of an orogen under extension: The case of the River Aniene in the central Apennines (Italy)

Abstract

In the retro-wedge side of a mountain chain undergoing back-arc extension, the progressive development of the fluvial network is controlled by the interaction of the uplift of the orogen, the activity of tectonic structures, and the climate. Many studies have evidenced the continuous competition between the activity of the normal faults that generate intermontane basins and rivers that incise and erode headward. Less attention has been paid to the role of the extensional structures that border the basins at the foot of the orogen and close to the base level (the back-arc basin) in the development of the hydrography draining their footwall. Could these structures influence or even prevent the integration of the fluvial network into the retro-wedge side of an uplifting orogen? To answer to this question, we studied the Aniene R., a tributary of the Tiber R. that drains the western side of the central Apennines (Italy). Studying the geometry of the topography and hydrography of its basin, surveying some key areas, dating deposits, and inverting its longitudinal profile, we reconstructed the landscape evolution of the drainage basin. In particular, we provide new evidence on the involvement of the structures bordering the low-standing extensional basins in the drainage development. Indeed, the flexural uplift of their footwall can hamper their flow down to the base level closing temporary the upstream drainage basin and so influencing the alternating phases of erosion and deposition controlled by uplift and climate.