Topographic metrics in the Southern Sector of the Marche Foothills: possible implication of Rock Uplift and active Tectonics

The investigated area is situated in central Italy and it extends from the axial zone of the UmbriaMarche Apennines to the Adriatic Sea, including the southern sector of the Marche Region and belongs to the foredeep domain of the Apennines orogenic system, which has affected by tectonic activity up to very recent times. The rheology of outcropping deposits doesn't allow the strain to be easily recorded at the outcrop scale. Thus, the quantitative geomorphic analysis can be provided a useful contribution to the study of recent tectonics. Some parameters, that quantify the channels morphology, as the Stream Length-Gradient (SL) Index [...] and the Steepness (Ks) Index [...], are generally used to detect anomalies on the expected concave-up equilibrium stream-profile, which can result in local abrupt changes in stream gradient (i.e., knickpoints) and/or broad convexities on stream long-profiles extending for tens of kilometres (i.e., knickzones). The main goal of this work is the study of the morphological and morphometrical features in the southern sector of the Marche Region, with the aim to gain new knowledge on the influences of rock resistance and rock uplift on the fluvial and topographic system. The analyses have been aimed at to test the sensitivity of both SL and Ks for evaluating active crustal deformations, acting at different wavelengths on land surface, within a low tectonically active thrust-and-fold belt. Additional purpose was the understanding of the pattern of regional differential crustal activity in the topographic arrangement of the study area. In this research project two sets of analysis were conducted. The first analysis was aimed at defining quantitatively the geometry of stream long-profiles along six adjacent trunk-valleys through different morphometric parameters. The objective of this first analysis was to identify and characterize the stream reaches and/or segments where the long-profiles exhibit anomalies on the typical concave up steady-state profile, respectively knickpoints and/or knickzones, possibly related to the activity of crustal deformation acting at different wavelengths. With the second analysis were investigated the general topographic features focusing on the spatial variation in the minimum, mean, and maximum elevations and in local relief values. To study topography at regional scale, were computed three swath profile, local relief map and topographic spatial filters at four different wavelengths. The results obtained from this work highlight, in the investigated area, four anomalies areas that are compatible with the sectors of the Periadriatic basin, split by transverse and oblique faults and on which a different tectonic and sedimentary evolution are present [...]. Notably, the crustal differential uplift demonstrated to be the main process responsible for the formation of knickzones along the middle portions of the major rivers draining this sector of the Marche foothills. The quantitative dataset has shown useful for detecting large topographic features transversal to the trend of the main regional morphostructures, which revealed effective on controlling stream long-profiles and relief. Moreover, the combine method used in this work (stream channel metrics and topography analysis) provides an advantageous approach in an area characterized by lithologies that are unlikely to preserve o tectonic deformation, where the longitudinal profile channel analysis is not sufficient to identifies anomalies.