Evoluzione morfotettonica del settore meridionale della dorsale del Monte Baldo (Prealpi Venete)

Morphotectonic evolution of the southern sector of the Mt. Baldo chain (Venetian Prealps, Italy)

Abstract

The morphostructural evolution of an area belonging to the south-eastern sector of the Giudicarie belt (Mt. Baldo chain, Venetian Prealps, Southern Alps) is examined here. The geological structure of this belt is the consequence of Late Miocene tectonics, characterised by thrust faulting towards the ESE. Ridges and valleys show a NNE-SSW direction; the ridges have a homocline structure dipping to the west and are delimited towards the east by tectonic scarps, which form the right slope of large asymmetrical valleys. Frequent surface evidences of neotectonic activity are ribbon-like fault scarps, dipping eastward as well as westward, that affect the major slopes. In the southern sector of the Monte Baldo chain, the neotectonic activity is particularly evident. It is characterised by collapse surfaces or scarps that predominantly dip eastward and indicate superficial gravity tectonics with mass transport in that direction. The most imposing scarps crop out near the summit of the ridge where a karst topography, characterised by a high density of dolines, is cut and displaced. One of the scarps strikes parallel to the «ridges of Naole», splitting the ridge itself. The intermediate furrow is approximately 30–50 m deep and runs parallel to the ridges for a few kilometres. Near its base, a ribbon-like scarplet, 1–1.5 m in height, testifies to a recent, probably Holocene, episode of surface faulting. The south-eastern slope of the main ridge is characterised by a complex pattern of uphill- and downhill-facing scarps as well as by patterns of concentric scars that support the hypothesis of detachment of large rock bodies. Downslope, wide outcrops of «syntectonic breccias» (sensu Coz-ZAGLIO, 1933) further strengthen the image of active slope tectonics. It represents the superficial expression of a regional compressive tectonics still in progress in the Giudicarie belt, as is independently suggested by seismotectonic data.