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

Abstract

Growth of topography in the Apennines has been driven by active tectonics (thrust-related crustal shortening and high-angle normal faulting related to crustal extension), regional rock uplift, and surface processes. Deep erosion has locally removed depositional growth strata leaving progressive unconformities genetically related to geomorphic features that can be used to interpret Apennine geologic history. We present a geomorphic and morpho-structural analysis of an understudied, 400 km² part of the central-southern Apennines covering Abruzzo, Lazio, and Molise regions thought to have emerged during the Early Pliocene and been subjected to protracted, deep erosion since then. Our study reveals a high-relief landscape dominated by several morphostructures including high-standing, resistant Mesozoic and early Tertiary carbonates and intervening, erodible Tertiary siliciclastics. Quaternary deposits are few, scattered, and cannot generally be used for reconstructing paleo-base levels; however, this study defines and identifies several paleo-uplands and pediments that may be linked to paleo-base levels. Cross-cutting relationships between the morphostructures, uplands, and pediments define the long-term geomorphic evolution of the area. Thrust and strike-slip faults were active only in the Miocene and Pliocene whereas the normal faults have been active during the Quaternary. The carbonate ridges were exhumed from the softer siliciclastics mostly in the Pliocene and a pre-Pliocene low relief upland was deeply incised. The base level fall driving this exhumation and incision is postulated to time the onset of regional rock uplift of the core of the southern Apennines to its present lofty mean elevation.