Detecting differential surface uplift at the orogen scale by topography and river network features: the Southern Apennines case study (Italy)

The growth of a mountain chain results from a complex interplay between endogenous and exogenous processes. The former depends on the geodynamic setting and cause the uplift of the orogenic wedge whereas the latter tend to erode the uplifted topography. Surface uplift may act at uneven temporal and spatial scale and reconstructing its distribution through space and time may provide fundamental data to unravel either the future tendency of geomorphic processes (e.g., increased erosion in uplifted areas) or to identify areas affected by active tectonics. In this study, we adopted a morphotectonic approach to unravel the spatial distribution of surface uplift in active orogens, such as the southern Apennines of Italy. Features of the topography (e.g., maximum, mean and minimum elevation maps, relief maps and swath profile) and the river network (e.g., river long profile and chi-long profile, Ksn index, chi index map) have been derived through ArcGis and Matlab softwares. The combined analysis of all indexes allows recognising a locus of enhanced surface uplift that moves from NE (the Bradanic foredeep) to the SW (the outer sector of the orogenic wedge). Surface uplift do not extend towards the inner sector of the orogenic wedge and its spatial distribution roughly follow the main divide. Furthermore, a natural tendency of the main divide to shift towards the NE has been also identified, that is consistent with the uneven spatial distribution of vertical motions. To quantify differences in surface uplift between the foredeep-outer chain and the inner chain, we analysed published data about MIS5 paleoshorelines. These data also confirmed the uneven distribution of surface uplift at the orogen scale, thus confirming that the adopted morphotectonic approach may be considered a powerful tool to constrain the spatial distribution of vertical motions.