Fluvial inverse modelling for inferring the timing of Quaternary uplift in the Simbruini range (Central Apennines, Italy)

The regional topography of the Central Apennines results from convergence between the African and Eurasian plates that led to the formation of a Neogene NE-verging imbricate fold and thrust belt. During the final stages of the orogenic deformations, the whole area was affected by strong uplift and by extensional faulting oriented along the main direction of the Apennine chain. In this framework, the landscape evolution in subaerial conditions started diachronically and is testified by the relicts of clastic deposit at different height from base levels of the present drainage network. In the Simbruini range, there are no absolute dating records neither of the most ancient clastic units deposited after the Messinian thrust-top facies nor of tectonic events. Trying to fill this gap, we used geomorphometric analyses to infer the timing of the recent phases of the tectonic history of the Simbruini range. Specifically, we identified the main non-lithological knickpoints along the river longitudinal profiles, clustered their altimetric distribution and correlated them with the levels of continental clastic deposits reserved at different elevations. Furthermore, we inferred the uplift history of the range by applying the inverse modelling of the river longitudinal profiles. Assuming a block uplift model, the drainage network cutting the Simbruini range recorded on average about 2.4 Myr of tectonic history, characterized by variable base level fall rates (corresponding to uplift rates). According the average tectonic history, the highest base level fall rate of 690 m My-1 was reached at 1.65 Ma, followed by the minimum of about 370 m My-1 , reached at 0.75 Ma, and by a second rise, up to a present-day value of 660 m My-1 .