The end-moraine systems in the Alpine piedmont plain in Northern Italy have been surveyed and interpreted since the XIXth Century, including the first attempts to interpret their origin. Moraine systems were used by Penck and Brückner (1909) for their model of Quaternary glaciations and subsequently many of them had been surveyed in three different editions of the Italian Geological Map. The stratigraphy of these systems in the old map series (the I and II edition of the Italian Geological Map, dating back to the last century, at a scale 1:100,000) reflected the Penck and Brückner (1909) model of four different glaciations, and they were mapped using a mix of litho- and climatostratigraphic units. These criteria were also applied to correlate end-moraine systems of different glacial basins and their outwash plains, including the terraced surfaces. However, the lacking of data hampered their precise age-attributions, so until the last series of geological maps (CARG Project, at a scale 1:50,000, encompassing the last two decades) their age was based mostly on the soil development and few biostratigraphical data. In the CARG Project, geological maps were surveyed at a more detailed scale (1:5,000 and 1:10,000), using an allostratigraphic approach and applying the Unconformity-Bounded Stratigraphic Units (UBSU). The detection of discontinuities became relevant in the unit subdivision of the end-moraine systems. Dedicated drillings, combined with systematic application of cross-dating methods (e.g.: 14C, palynology, paleomagnetism, cosmogenic 10Be), also allowed to better depict the stratigraphic architectures of the end-moraine systems, highlighting significant differences from one system to another. Some glacial apparatus show more than four units ascribable to different glaciations (e.g.: Ivrea and Rivoli-Avigliana morainic amphitheatres), whereas others show remnants of less glaciations (e.g.: Piave and Tagliamento morainic amphitheatres). Using this approach, the resulting correlation with the outwash deposits became stronger thanks to the detailed study of subsurface stratigraphy; this also let to develop a more constrained stratigraphy throughout the Po Plain. The relationship between the end-moraine systems and the deposits of the related mountain catchments were performed through allostratigraphic profiles, which also showed the ice-elevation of the younger glaciations in the lower reaches of the valleys. In some cases, the low distance with the coastline allowed to trace the discontinuities from the end-moraine systems to the continental/marine transitions and to separate units ascribed to different glaciations. The resulting architecture of the end-moraine systems at the scale of the whole Po Plain, from the Piedmont Plain to the Veneto-Friuli Plain, can now be used as a tool for better depicting the evolution of the glacial advances in the southern slope of the Alps. References Penck A, Brückner E. 1909. Die Alpen im Eiszeitalter. Tauchnitz: Leipzig.
Geological mapping of end-moraine systems in Northern Italy: a long-lasting story of survey, stratigraphy and age-assessment
Giovanni Monegato;Gianfranco Fioraso;
2019
Abstract
The end-moraine systems in the Alpine piedmont plain in Northern Italy have been surveyed and interpreted since the XIXth Century, including the first attempts to interpret their origin. Moraine systems were used by Penck and Brückner (1909) for their model of Quaternary glaciations and subsequently many of them had been surveyed in three different editions of the Italian Geological Map. The stratigraphy of these systems in the old map series (the I and II edition of the Italian Geological Map, dating back to the last century, at a scale 1:100,000) reflected the Penck and Brückner (1909) model of four different glaciations, and they were mapped using a mix of litho- and climatostratigraphic units. These criteria were also applied to correlate end-moraine systems of different glacial basins and their outwash plains, including the terraced surfaces. However, the lacking of data hampered their precise age-attributions, so until the last series of geological maps (CARG Project, at a scale 1:50,000, encompassing the last two decades) their age was based mostly on the soil development and few biostratigraphical data. In the CARG Project, geological maps were surveyed at a more detailed scale (1:5,000 and 1:10,000), using an allostratigraphic approach and applying the Unconformity-Bounded Stratigraphic Units (UBSU). The detection of discontinuities became relevant in the unit subdivision of the end-moraine systems. Dedicated drillings, combined with systematic application of cross-dating methods (e.g.: 14C, palynology, paleomagnetism, cosmogenic 10Be), also allowed to better depict the stratigraphic architectures of the end-moraine systems, highlighting significant differences from one system to another. Some glacial apparatus show more than four units ascribable to different glaciations (e.g.: Ivrea and Rivoli-Avigliana morainic amphitheatres), whereas others show remnants of less glaciations (e.g.: Piave and Tagliamento morainic amphitheatres). Using this approach, the resulting correlation with the outwash deposits became stronger thanks to the detailed study of subsurface stratigraphy; this also let to develop a more constrained stratigraphy throughout the Po Plain. The relationship between the end-moraine systems and the deposits of the related mountain catchments were performed through allostratigraphic profiles, which also showed the ice-elevation of the younger glaciations in the lower reaches of the valleys. In some cases, the low distance with the coastline allowed to trace the discontinuities from the end-moraine systems to the continental/marine transitions and to separate units ascribed to different glaciations. The resulting architecture of the end-moraine systems at the scale of the whole Po Plain, from the Piedmont Plain to the Veneto-Friuli Plain, can now be used as a tool for better depicting the evolution of the glacial advances in the southern slope of the Alps. References Penck A, Brückner E. 1909. Die Alpen im Eiszeitalter. Tauchnitz: Leipzig.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
