Ripiani litostrutturali, superfici terrazzate marine e tettonica quaternaria in località Tarsia (Valle del Crati, Calabria)

Abstract

The geological and morphological features of a small area, located between the Follone and Crati rivers about 35 km north of Cosenza (southern Italy) have been studied. Deposits dating to the late Miocene, early Pliocene and early-middle Pleistocene crop out in this area. Many subhorizontal surfaces with no detrital cover can be recognized along the southeastern slope (where the Tarsia village is located) at elevations decreasing from NE to SW; these surfaces are classified as lithostructural surfaces originating from a selective erosion (shown as P and M in figure 5 of the text). Surfaces shown as no. 2 in the figure 4 of the text correspond to the contact between Units 5 (gravel and sand) and 6 (clay) (shown in the figures 2 and 3 of the text). Surfaces shown as no. 1 mark the passage between Units 3 (arenaceous-algal layer) and 4 (clay) and between Units 1 (conglomerates) and 2 (stratified pelite) of the already mentioned figure 2. The elevation lowering of surfaces from NE to SW is given by NW-SE trending faults which displaced the mio-pleistocenic bedrocks before the formation of these surfaces. The watershed between the Follone and Crati rivers is characterised by the presence of terrace remains of marine origin and resulting from the emersion of the area at the end of early Pleistocene-beginning of middle Pleistocene. The lowering in elevation from NE to SW (from el. 311 to 282 m a.s.l.) is due to a mild activity of the NW-SE-trending faults (see fig. 2 of the text). The northwestern slope is modelled by terrace remains of marine origin with an inner margin at el. 270 m a.s.l.; the terraces probably date to the beginning of middle Pleistocene and, in the studied area, do not appear to have been affected by the NW-SE faults activity. It is concluded that the climax of activity of these faults occurred in early Pleistocene times during sedimentation and diminished rapidly, estinguishing in the middle Pleistocene.