Morphostructural setting of the Sangro and Volturno Rivers divide area (Central-Southern Apennines, Italy)

Abstract

Topography of the Apennines chain resulted from the combined action of tectonic displacements (related to thrusting and high-angle faulting), large-scale uplift and surface processes. In such mountainous settings, where strong erosion is often responsible for incomplete stratigraphic records of surface evolution of thrust belts, geomorphological analysis helps quantify these processes and provide a framework for interpreting the geologic history of these regions. We studied a 400 km2 area of the Central-Southern Apennines, covering Abruzzo, Lazio and Molise regions, by means of morphostructural analysis. This sector of the chain emerged during the Lower Pliocene and suffered a long-lasting erosion. Our study reveals a high relief landscape dominated by high-standing, resistant carbonates forming structure-controlled landforms (morphosculptures), and valleys underlain by erodible siliciclastics. Quaternary deposits are few and scattered, and they give poor constraints for the recognition of ancient base-levels. However, this study defines and identifies several upland erosional surfaces (paleosurfaces) that may be linked to ancient base-levels. On the basis of cross-cut relationships between paleosurfaces and structural landforms, we outlined a possible long-term geomorphological evolution of the study area. Most of the local tectonic displacements in this sector of the chain took place during Miocene and Pliocene, by means of thrusting and strike-slip faulting, whereas only localized extensional tectonics occurred during Quaternary times. Since the Pliocene, differential erosion promoted exhumation of carbonates and deep incision of pre-existing erosional surfaces. This strong erosion can be related to a regional base-level lowering promoted by large-scale uplift of the axial sector of the Central-Southern Apennines.