Morfologia, Geologia ed evoluzione neotettonica dei rilievi collinari di Buttrio-Dolegna del Collio (Friuli orientale)

Morphology, Geology and neotectonic evolution of the hills of Buttrio-Dolegna del Collio (eastern Friuli, Italy)

Abstract

The low hills rising from the plain South of « Cividale del Friuli », in which the « Flysch di Cormons » of an early Eocene age crops out, have been studied. These hills show a morphology that is characterized by a dense drainage network and by hundreds of accordant summits which differentiate this area from the adjacent piedmont zone to the East. The aim of this paper is to explain the origin and significance of the summit accordances by reconstructing the stages in the evolution of relief during the Quaternary period in the geologic and geodynamic framework of eastern Friuli. Laboratory techniques involved: a statistical analysis of the summit elevations, the study of topographic maps of different scales and the interpretation of aerial photographs. Morphology, lithology and Tectonics were studied on the field. Among the various results which arose are the « topographic reconstruction » of the hills and the structural maps; this analysis allowed us to identify five orders of concordant summits that constitute residual morphologies of ancient planation surfaces which lie at different elevations. The top surface, now corresponding to the highest accordant summits, is probably an erosion glacis, while the lower surfaces can be considered as river terraces formed as consequence of the uplifting of the area. The comparative examination of the morphological, lithological and tectonic analyses allowed us to formulate a kinematic model of the area during the Quaternary age.