This work aims to present a 1:50 000 scale geomorphological map of the Triangolo Lariano area, located between the two branches of the Como Lake, in Northern Lombardy, Italy. This zone is sited in the Sub-Alpine Domaine, where the main lithologies are calcareous, dolomitic or siliceous and the structural setting is linked mostly to the inherited structures of the Southern Alps neo-tectonic activities. From the geomorphological point of view, the area was subject to several processes, the main of which are fluvial/runoff, glacial and karst. Through field campaigns, remote sensing, like DEM and orthophotos analysis, an area of 258km2 was investigated in detail. Field surveys show that the study area was modelled by multiple processes in turn occurring in different geological periods. Multigenetic landforms of the pre-Messinian Age were subsequently influenced by karst processes, and then remodelled by the glaciers, most intensively during the Last Glacial Maximum. Examples include earth pyramids, formed from moraine material, and washed away by more recent run-off processes, or very long karst systems filled during the LGM, changing the drainage, or V-shaped valleys today become U-shaped valleys. Moreover, younger landforms were formed as a result of climate changes over the last centuries, such as river terraces and landslides. In addition, the landscape has also been shaped by humans, so that anthropogenic works can be observed, such as dams and check dams that inevitably have to interface with the processes in the area, so their functional and structural conditions were investigated in more detail in relation to the sources of the sediment they have to collect. The evidence found, allow new interpretations of the paleogeography of some parts of the area. In fact, two sites were chosen to develop some hypotheses: the Segrino Lake and the Pian del Tivano area. Concerning the Segrino Lake, some hypotheses reported in literature were investigated. In fact, using a DEM of 5x5m resolution, and derivatives thereof, such as the Analytical Hillshading, as well as geological maps and well stratigraphies, a potential fluvio-glacial origin of the Segrino Lake was hypothesised. On the Pian del Tivano, four soil profiles were carried out to document the origin of this particularly complex area affected by karst and glacial processes. Especially, the presence and origin of the polje, located at the foot of a Quaternary moraine in an area where lake sediments were found, was analysed. We assume following the arrival of the Adda glacier, that glacier streams shaped the plain. Subsequently, a periglacial period occurred during which permafrost formed blocking the underlying karst system, in turn creating a backwater mechanism and forming a lake. As a result of glacial retreat and climate change, the water was able to drain rapidly into the swallow holes present, leaving some “lake terraces” as evidence of this event. In conclusion, this thesis work contributes to future research developing a theoretical model for the evolution of an area that is of multigenetic origin, but at the same time fascinating from a morphologic, landscape and geological point of view.
Questo lavoro si propone di presentare una carta geomorfologica in scala 1:50 000 dell'area del Triangolo Lariano, situata tra i due rami del Lago di Como, nella Lombardia Settentrionale, Nord Italia. Questa zona è situata nel Sudalpino, dove le principali litologie sono calcaree, dolomitiche o silicee e l'assetto strutturale è legato soprattutto alle strutture ereditate dalle attività neotettoniche delle Alpi Meridionali. Dal punto di vista geomorfologico, l'area è stata soggetta a diversi processi, i principali dei quali sono fluviali/di ruscellamento, glaciali e carsici. Attraverso campagne sul campo, telerilevamento, analisi di DEM e ortofoto, è stata studiata in dettaglio un'area di 258 km2. Le indagini sul campo hanno dimostrato che l'area è stata modellata da molteplici processi avvenuti in tempi geologici diversi. Le forme del terreno sono multigenetiche, soprattutto di età pre-Messiniana e sono state successivamente influenzate da processi carsici e poi rimodellate dai ghiacciai, in particolare durante l'Ultimo Massimo Glaciale. Ne sono un esempio le piramidi di terra, formate da materiale morenico e dilavate da processi di ruscellamento più recenti, o i lunghissimi sistemi carsici che si sono riempiti durante l'LGM, modificando il drenaggio, o le valli a V oggi diventate valli a U. Inoltre, a seguito dei cambiamenti climatici degli ultimi secoli, si sono costituite forme più giovani, come terrazzi fluviali e frane. Il paesaggio è stato modellato anche dall'uomo, tanto che si possono osservare opere antropiche, come briglie e sbarramenti che inevitabilmente si interfacciano con i processi dell'area. Per questi motivi, le loro condizioni funzionali e strutturali sono state indagate più nel dettaglio in relazione alle fonti dei sedimenti che devono raccogliere. Le evidenze trovate hanno consentito anche nuove interpretazioni della paleogeografia di alcune zone dell'area. Infatti, per sviluppare alcune teorie sono stati scelti due siti: il Lago del Segrino e l'area di Pian del Tivano. Per quanto riguarda il Lago del Segrino, sono state indagate alcune ipotesi riportate in letteratura. Infatti, utilizzando un DEM di risoluzione 5x5m e derivati, come l'Analytical Hillshading, oltre a carte geologiche e stratigrafie di pozzi, è stata ipotizzata una potenziale origine fluvio-glaciale di questo lago. Per quanto riguarda il Pian del Tivano, sono stati eseguiti quattro profili di suolo per documentare l'origine di quest'area molto complessa, interessata da processi carsici e glaciali. In particolare, è stata analizzata la presenza e l'origine del polje, situato ai piedi di una morena risalente all’Ultimo Massimo Glaciale in un'area in cui sono stati rinvenuti sedimenti lacustri. Si ipotizza che dopo l'arrivo del Ghiacciaio dell'Adda i torrenti provenienti dal suo fronte, abbiano modellato la piana proglaciale antistante la morena. Successivamente, durante un periodo periglaciale, il permafrost formatosi ha bloccato il sistema carsico sottostante, creando a sua volta un meccanismo di ristagno e formando un lago. A seguito del ritiro glaciale e dei cambiamenti climatici, l'acqua è stata in grado di drenare nuovamente e rapidamente negli inghiottitoi presenti, lasciando alcune "terrazze lacustri" a testimonianza di questo evento. In conclusione, questo lavoro di tesi contribuisce alla ricerca futura sviluppando un modello teorico per l'evoluzione di un'area di origine multigenetica, ma allo stesso tempo affascinante dal punto di vista morfologico, paesaggistico e geologico.
Indagini geomorfologiche dell'area del Triangolo Lariano, Italia settentrionale: una sintesi multigenetica
SIMONCELLI, LAURA
2021/2022
Abstract
This work aims to present a 1:50 000 scale geomorphological map of the Triangolo Lariano area, located between the two branches of the Como Lake, in Northern Lombardy, Italy. This zone is sited in the Sub-Alpine Domaine, where the main lithologies are calcareous, dolomitic or siliceous and the structural setting is linked mostly to the inherited structures of the Southern Alps neo-tectonic activities. From the geomorphological point of view, the area was subject to several processes, the main of which are fluvial/runoff, glacial and karst. Through field campaigns, remote sensing, like DEM and orthophotos analysis, an area of 258km2 was investigated in detail. Field surveys show that the study area was modelled by multiple processes in turn occurring in different geological periods. Multigenetic landforms of the pre-Messinian Age were subsequently influenced by karst processes, and then remodelled by the glaciers, most intensively during the Last Glacial Maximum. Examples include earth pyramids, formed from moraine material, and washed away by more recent run-off processes, or very long karst systems filled during the LGM, changing the drainage, or V-shaped valleys today become U-shaped valleys. Moreover, younger landforms were formed as a result of climate changes over the last centuries, such as river terraces and landslides. In addition, the landscape has also been shaped by humans, so that anthropogenic works can be observed, such as dams and check dams that inevitably have to interface with the processes in the area, so their functional and structural conditions were investigated in more detail in relation to the sources of the sediment they have to collect. The evidence found, allow new interpretations of the paleogeography of some parts of the area. In fact, two sites were chosen to develop some hypotheses: the Segrino Lake and the Pian del Tivano area. Concerning the Segrino Lake, some hypotheses reported in literature were investigated. In fact, using a DEM of 5x5m resolution, and derivatives thereof, such as the Analytical Hillshading, as well as geological maps and well stratigraphies, a potential fluvio-glacial origin of the Segrino Lake was hypothesised. On the Pian del Tivano, four soil profiles were carried out to document the origin of this particularly complex area affected by karst and glacial processes. Especially, the presence and origin of the polje, located at the foot of a Quaternary moraine in an area where lake sediments were found, was analysed. We assume following the arrival of the Adda glacier, that glacier streams shaped the plain. Subsequently, a periglacial period occurred during which permafrost formed blocking the underlying karst system, in turn creating a backwater mechanism and forming a lake. As a result of glacial retreat and climate change, the water was able to drain rapidly into the swallow holes present, leaving some “lake terraces” as evidence of this event. In conclusion, this thesis work contributes to future research developing a theoretical model for the evolution of an area that is of multigenetic origin, but at the same time fascinating from a morphologic, landscape and geological point of view.È consentito all'utente scaricare e condividere i documenti disponibili a testo pieno in UNITESI UNIPV nel rispetto della licenza Creative Commons del tipo CC BY NC ND.
Per maggiori informazioni e per verifiche sull'eventuale disponibilità del file scrivere a: unitesi@unipv.it.
https://hdl.handle.net/20.500.14239/14603