CONSTRAINING MOUNTAIN FRONT ACTIVITY IN ACTIVE EXTENSIONAL SETTING BY TECTONIC GEOMORPHOLOGY: CASE STUDIES FROM THE SOUTHERN APENNINES (ITALY)

The southern Apennines is a fold-and-thrust belt, which was formed during the late Cenozoic convergence between the African and Eurasian plates. Late Quaternary and active tectonics are dominated by extensional faulting mainly acting in both the inner and the axial belts of the mountain belt. Since the Early-Middle Pleistocene, activity of high-angle normal faults caused the formation of large coastal grabens and intramountain basins that are often limited by mountain fronts, up to 2000 high, formed in carbonate rocks. Late Quaternary activity of some of these high-angle normal faults, that mainly trend NW-SE and E-W, has been proved through field geomorphological and/ or stratigraphical and structural data and could be inferred by quantitative investigation of landforms. To test the suitability of the quantitative analysis approach to assess the state of activity of faults placed at the boundaries between mountain fronts and alluvial basins, and to verify the limits of applicability of this method, we have carried out a comprehensive analysis of some mountain fronts in the Southern Apennines. We have compared the following indexes: mountain front sinuosity, swath profile, river long profile, slope/area data, alluvial fan and drainage basin metrics. Overall data point to variable geomorphic features of different mountain fronts and along-strike variability of some parameters at the mountain front scale in response to either rock-type resistance or fault behaviour. This study highlights the importance of the tectonic geomorphology approach in active orogens and suggest that this method is suitable to application worldwide to compare mountain front maturity.