Contributo alla definizione del limite tra evidenze di neotettonica e fenomeni dovuti ad altre cause

Contribution to a definition of the limit between signs of neotectonic activity and other causes

Abstract

This paper describes various examples of geomorphological research, which in close relation to stratigraphic, geopedological, structural-geological data as well as other data, permitted either the identification of activity or the exclusion of the presence of «linear neotectonic elements». The examples described are situated in northeastern Italy. A normal fault has displaced by a few meters morainic deposits of the Upper Pleistocene on the eastern side of Lake Garda in the area of S. Vigilio. Along the Modena Apennine margin between Sassuolo and Maranello, marine sediments of the Lower Pleistocene proved to be arranged vertically or overturned by a tectonic element that could not be identified with certainty (flexure, breakthrough, or fault). New data confirm Holocene activity of a fault in the area of Mazzin (Dolomites). Morphological signs of recent activity of faults revealed in the subsurface were identified in the area of Mantova by means of seismic prospecting. Neotectonic phenomena are excluded in the case of fluvioglacial faulted deposits of the Upper Pleistocene revealed in the vicinity of Manerba and Desenzano (western side of Lake Garda) and in the vicinity of Dolcè (lower Adige Valley). In conclusion, the authors confirm the importance of carrying out thorough investigations before attributing tectonic causes to evident faulting or folding, even when Quaternary deposits are involved. They also stress that even in more detailed studies there may be some amount of uncertainty as to the nature and characteristics of the phenomenon examined. When the tectonic nature of the phenomenon has been identified, but elements for precise dating are lacking, it is possible to date a tectonic movement by analyzing the relationships existing between deposits whose age is certain and geomorphological evidence linked to the movement itself.