Relationship between karstic landforms and neotectonic in the western Marsica (Central Appenine, Italy) inferred from photogeological analisys.

The aim of this work is to show the relationship between karstic landforms and neo-tectonics in the southern sector of the Western Marsica region. The investigated area is located in the Colle Rotondo-Colle Terelle structure (southern Latium) between the towns of Pescosolido and Alvito. It is an elongated Apennine-trending morphological place, bounded by some of the most relevant regional tectonic features of the whole Apennines, such as the Simbruini-Ernici Mts. leading thrust and the Val Roveto-Atina-Caserta line. Here the Meso-Cenozoic carbonate deposits of the Latium-Abruzzi sequence, the Upper Miocene terrigenous and Plio-Quaternary continental deposits outcrop. In more detail the area belongs to a sector of the Apennines, which has been intensively deformed by Neogene-Quaternary compressional and extensional tectonics. This sector of the chain mostly formed in Neogene times in the context of the eastwards piggy-back propagation of thrust sequence and was broken up by Plio-Quaternary distensive tectonics. Intepretation of aerial photographs and field surveys allowed a detailed analysis of hydrography, karstic morphology and Quaternary tectonic evidence. The Colle Rotondo-Colle Terelle structure is a still active karstic area; the coexistence of epigeous forms and processes at different grades of evolution makes it a nearly unique zone. At the foot of the structure the copious Fibreno springs are located, which act as the present base level for karstic erosion. Along the Apenninic-trending tectonic alignments the greatest karstic phenomena of the whole area are present. The main dolines of the area, developed along tectonic directions with Apennine trend, show morphological evidence of stasis periods in their evolution, related with Quaternary tectonic activity. They are represented as different erosional surfaces within the dolines themselves as well as abandoned valleys. The analysis and classification of the both karstic forms and their mutual relationships show that the main Quaternary tectonic events modified the karstic morphogenesis