Geomorfologia quantitativa e morfoneotettonica nell'area di Morlupo-Castelnuovo di Porto nei Monti Sabatini (Lazio)

Quantitative Geomorphology and Morphoneotectonics of the Morlupo-Castelnuovo di Porto area (Monti Sabatini, Latium)

Abstract

Within the Sabatini Volcanic Complex, active between 0.6 and 0.05 million years before present, the easternmost section, extending from Riano as far as Castelnuovo di Porto, is considered; the aim is to evaluate how recent tectonics have influenced the present landforms. This area is located on the eastern edge of the graben in which the whole Sabatini volcanism evolved, and is the place where the Morlupo–Castelnuovo di Porto eruptive center developed about 0.6 million years ago. This center, the oldest of the eastern sector of the volcanic complex, is not discernible in the field, but its pyroclastics cover most of the studied area, even though some products of the westernmost and younger Sacrofano center are present. Morphodynamic processes are particularly marked throughout the area; the morphogenetic action is mainly due to channeled running waters, which cut the volcanic cover very deeply, often exposing the Plio-Pleistocene clayey-sandy lithotypes. Morphographic and morphometric characteristics of drainage networks show that many anomalies exist in the spatial arrangement and in the flow direction of fluvial channels, the latter often being inconsistent with regional and local slopes. Moreover, the parameters of index and density of hierarchical anomaly generally show anomalous values, which testifies to a poor organization of the drainage networks. Furthermore, the areal distribution of drainage density and relief energy values, calculated per unit area, shows frequent irregularities that cannot be explained by lithological conditions alone. These irregularities, the peculiar geometry of drainage networks, and their low degree of hierarchical organization, taken as a whole, suggest that watercourse directions are strictly controlled by deep structures. Field surveys show that many morphological situations are clearly dependent on recent tectonics; many morphotectonic evidences allow the identification of three main tectonic alignments trending respectively NW–SE, NE–SW, and N–S. Finally, by framing these alignments in a regional context, an attempt is made to establish the role they played in defining the morphological evolution of the area.