Studio geomorfologico e geoarcheologico della zona di Rovereto nel quadro dell'evoluzione olocenica del settore Trentino della Valle dell'Adige

This thesis was realized in cooperation with the Soprintentenza dei Beni Librari, Archivistici e Archeologici of the Provinica Autonoma di Trento and the company C.O.R.A. Ricerche Archeologiche. The reaserch aimed at investigating the geomorphological evolution of the valley of Adige River in the last 2000 years and especially in the period between the end of the Roman epoch and the early Medieval period, seeking for possible relations existing between the environmental changes occurred in that period and the dynamics of the human population. This work considered thesector of the Adige River Valley belonging to the Provincia Autonoma di Trento (North-eastern Italy) from Mezzocorona to Avio, for a total length of about 65 km and an extent of 285 km2. The area was investigated through remote sensing, in particular considering the DTM obtained by Laser altimetry (LiDAR, surveyed in 2006-2007) and analyzing the aerial pictures at scale 1:10.000 (surveyed 1994, 2000, 2006). The information was checked with the data of the new geological map available for the area (Project CARG). This combined work led to produce the geomorphological map of the whole area at 1:10.000 scale and printed at 1:20.000 (attached to this thesis). As a specific case study, this thesis focused on the area of Rovereto, 20 km south of Trento, that is quite famous among the geological community for the existence of the huge landslide deposit named “Lavini di Marco”, mentioned by Dante in the Divina Commedia (Inferno, Canto XII). This is a complex deposit, consisisting of different bodies and which have been investigated by several geologists and recently dated through esposure datings.New information about the evolution of the area has been collected through the geoarchaeological investigation carried out in the archaeological site of Navicello, near the present Adige River, about 0.5 km upstream of the major landslide deposit where, in 2012, a Roman villa and some late-Antiquity structures had been excavated. The youngest archaeological findings date back to the 5-6th century AD and they are covered by 2-3 m of sandy alluvial deposits related to the flooding activity of Adige. The stratigraphic setting, the thickness and the extent of the depositional unit burying the site have been investigated analyzing the pre-existing geotechnical stratigraphies available in the valley floor near Rovereto and realizing about 30 new boreholes. These reached a depth between 1.5 and 4.7 m and were realized using a handauger equipment. The combined use of LiDAR, aerial pictures and field data allowed to dimostrate that the depositional unit covering the site form one of the largest fluvial terraces along the Adige Valley. This terrace is about 6 m above the present mean level of Adige and, 6 from east to west, it extends from the present river until the eastern slope of the valley near Lizzana 1.3 km); from north to south the terrace is present between the alluvial fan of Leno Creek, near Rovereto, and the northern limit of the Lavini di Marco Landslide (1 km). The top of the terrace is flat, almost lacks of any inclination and its elevation is between 171-172 m a.s.l. This value is exactly matching with the top of the landslide deposit existing along the present Adige channel, were they are only at 70 m of distance from the western bedrock slope. These data allowed to demonstrate that the main body of the Lavini di Marco landslide caused the temporary damming of the Adige River, triggering the formation of an alluvial plain occupying the whole width of the valley. After a relatively short period, the river eroded part of the slope deposit and restored the pre-existing fluvial profile, entrenching also the alluvial units thatbudied the post-Roman site. Thus, the new evidence highlights that the Lavini di Marco landslide occurred after 6th century and it is likely that it matches with the lansdlide described in the historical chronicles “Fulda Annales” in the 883 AD.