Alluvial megafans are not very common in Europe and the use of this term is not diffuse in the continent because of the persistent habit of describing as "fans" event the huge divergent alluvial landforms (>1000 km²). Considering the megafans that are currently still recognizable in the topography, they can be found only in some of the alluvial areas facing the Alps and the Carpathian chain. Along the southern Alps, megafans are present from Milan (central Po Plain) to the whole Venetian-Friulian Plain. The major landforms are the ones formed by Adda, Olona, Oglio, Adige, Brenta, Piave and Tagliamento rivers. All these systems experienced a strong depositional phase in the LGM (29-17.5 ka BP), when the Alpine glaciers stationed at the mouth of their valleys and the rivers played as glacial outwashes. Sedimentary starvation characterized all the megafans of northern Italy since Late Glacial. Thus, the Alpine megafans can be mainly considered as relict products of the last glaciation, mainly controlled by the climate forcings. Megafans are documented also in the Little Hungarian Plain (Danube River near Bratislava and Rába River megafans; mainly fed by the Alps) and in the Great Hungarian Plain (e.g. megafans of Maros, Szamos and Timis rivers). The largest megafan is the one formed by the Maros River, which consists of two lobes covering an overall area of at least 7000 km². The dated traces of braided and meandering channel belts testify a continuative activity until late Holocene. Compared to the Alpine ones, the megafans of the Great Hungarian Plain are fed by larger catchments, but these were not severely glaciated during LGM and sustained important depositional phases also in Late Glacial and after. In the Carpathian Basin the megafan evolution was strongly influenced by differential subsidence.
Alluvial Megafans of Europe: Morphologies, Architectures and Formation Phases
Fontana A.
;Mozzi P.
2017
Abstract
Alluvial megafans are not very common in Europe and the use of this term is not diffuse in the continent because of the persistent habit of describing as "fans" event the huge divergent alluvial landforms (>1000 km²). Considering the megafans that are currently still recognizable in the topography, they can be found only in some of the alluvial areas facing the Alps and the Carpathian chain. Along the southern Alps, megafans are present from Milan (central Po Plain) to the whole Venetian-Friulian Plain. The major landforms are the ones formed by Adda, Olona, Oglio, Adige, Brenta, Piave and Tagliamento rivers. All these systems experienced a strong depositional phase in the LGM (29-17.5 ka BP), when the Alpine glaciers stationed at the mouth of their valleys and the rivers played as glacial outwashes. Sedimentary starvation characterized all the megafans of northern Italy since Late Glacial. Thus, the Alpine megafans can be mainly considered as relict products of the last glaciation, mainly controlled by the climate forcings. Megafans are documented also in the Little Hungarian Plain (Danube River near Bratislava and Rába River megafans; mainly fed by the Alps) and in the Great Hungarian Plain (e.g. megafans of Maros, Szamos and Timis rivers). The largest megafan is the one formed by the Maros River, which consists of two lobes covering an overall area of at least 7000 km². The dated traces of braided and meandering channel belts testify a continuative activity until late Holocene. Compared to the Alpine ones, the megafans of the Great Hungarian Plain are fed by larger catchments, but these were not severely glaciated during LGM and sustained important depositional phases also in Late Glacial and after. In the Carpathian Basin the megafan evolution was strongly influenced by differential subsidence.
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