Tezza, Filippo (2015) Studio geomorfologico delle Valli Grandi Veronesi (bassa pianura veneta). [Magistrali biennali]
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The object of this thesis is a geomorphological study made in the area known as Valli Grandi Veronesi, which is located in the venetian distal plain, 35 km south of Verona, next to the Emilia Romagna and Lombardia regions. Topographically, this zone appears sunken and from a morphological point of view it is characterized by a basin (which explains its name “Valli”). For this reason, and due to an insufficient drainage pattern of the hydrographic network coming from upstream, in the past this area was prone to flooding and swamping. During the XIX century, a far-reaching and intensive land reclamation project was carried out in order to recover this territory. The land reclamation was only concluded in the second half of the XX century. At present, the plain of the Valli Grandi Veronesi is still mainly an agricultural territory and has not yet been affected to a great extent by human impact. This area has always been studied by geoarchaeologists because it offers a great variety of exceptionally well-preserved ancient natural landforms, as well as anthropic elements that testify the presence of human intervention from the Bronze age onwards. At present, these forms are still detectable on the ground and visible through remote sensing images. In particular, the main ancient Terramara villages, such as Castello del Tartaro, Fabbrica dei Soci and Fondo Paviani (all Bronze age settlements), have been widely investigated in the past, and together with the roman centuriae traces, they represent a key element for the historical interpretation of the Valli Grandi Veronesi. Our research, in particular, is focused on the identification, the morphology and the dating of the ancient paleochannels of the Adige River, as well as the incised valleys where the resurgence springs flowed. The photointerpretation (using orthophoto maps and remote sensing images with the ArcMap 10.2© software) has been the starting point to study the ancient natural and anthropic landforms that can be observed in this territory. The availability of a Digital Terrain Model (DTM), obtained by the modern technology of LiDAR acquisitions taken during 2012, was crucial to analyze in detail the topographic altitudes of a morphologically depressed and flat territory like the Valli Grandi Veronesi. This highly detailed DTM enabled us to map many geomorphological elements like fluvial ridges and incised valleys, and gave us the opportunity to extract some topographic profiles with extremely accurate data, never obtained for this area before. For the most part, this thesis is based on two detailed on-site geological surveys, in which forty-four cores were drilled with a hand auger, and the respective stratigraphic logs were later drawn with the Adobe Illustrator CS4© software. During the first geological survey, carried out between March and April 2015, six cross sections were made through some geomorphological elements like crevasse splays, paleochannels and flood plains, in order to analyze the composition of their first meters of alluvial deposits. The second and last geological survey was conducted in July 2015 with the drilling of some single cores, whose positions were specifically chosen in order to broaden our knowledge of some little-known aspects related to the geomorphological evolution of this area. An on-site geophysical prospection was also made in July 2015, by extending two Electrical Resistivity Tomography (ERT) lines across the Fabbrica dei Soci paleochannel, which had already been studied with a cross section during the first geological survey. Some of the single cores drilled during the second geological survey have confirmed the presence of a second incised branch of the Menago River paleovalley. The main branch of this fluvial incised valley was indeed known since the first studies were made in this territory, but only the highly detailed DTM, obtained by LiDAR altimetry acquisitions, 6 have revealed a second supposed branch as well, incised into the ancient Adige River megafan. Therefore, the on-site single cores have allowed us to verify the actual presence of the second incision, which is detached from the main branch of the Menago River incised valley. The overall collected data, in particular those obtained thanks to the two geological surveys, also made it possible to detect some fundamental features of the Last Glacial Maximum (LGM) fluvial sediments of the Adige River, which are partly outcropping (mainly in the northwesterly part of the studied area) and partly buried under the most recent Adige and Po Rivers’ deposits (indicated as post-LGM deposits). Both the photointerpretation activity and the DTM data analysis, in addition to the collected geological and geophysical data and the data obtained through bibliographic sources, have allowed us to create a Geomorphological Map of the Valli Grandi Veronesi (scale 1:25.000). The newly-gathered data, finally, have contributed to the ongoing exploration of this particular southwestern venetian plain territory and have outlined some new hypotheses about its geomorphological development. It is hoped that, in the future, the Valli Grandi Veronesi area will be the object of further investigations and analyses from a geomorphological and geological viewpoint
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