Abstract
ABSTRACT The Rivoli-Avigliana end moraine system (Italian Western Alps) hosts an important stratigraphic archive of Pleistocene glaciations. A new geological map provides a 3D architecture of the system that reveals a complex architecture of glacial, alluvial and lacustrine units. Six glacial units were recognized. During the deposition of the four older glacial units (Early-Middle Pleistocene) the morphology of the valley outlet had a different drainage pattern from the present, with the presence of large lakes. From the penultimate glaciation to the Last Glacial Maximum (LGM) the piedmont lobe was confined within the valley, never extending towards the alluvial Po Plain. The LGM is characterized by two glacial advances and four distinct recessional phases during the Lateglacial. The presence of a bedrock inselberg affected the flow of the glacier front, which should have had weak erosive strength as shown by the preservation of lacustrine deposits below the glacial units.
Highlights
The glacial end moraine systems, called morainic amphitheatres, are characteristic glacial landforms of Alpine valley outlets
The stratigraphic architecture of an end moraine system is strongly influenced by the configuration and dynamics of the glacial piedmont lobe and of the terminal moraines
Thanks to the results of a recent subsoil exploration campaign and new radiometric dating, in this paper we present a new stratigraphic architecture and a more accurate chronostratigraphy of the RivoliAvigliana morainic amphitheatre
Summary
The glacial end moraine systems, called morainic amphitheatres, are characteristic glacial landforms of Alpine valley outlets They are the result of multiple advances of glacial piedmont lobes, which spread out from the European Alps during the Pleistocene cold periods. Their stratigraphic reconstruction promoted, since the late nineteenth century (Gastaldi, 1872), the concept of glaciations and the development of the fourfold chronostratigraphic subdivision of Penck and Brückner (1909). The shape of the valley outlet, the inheritance of the river thalweg, and the presence of irregular bedrock morphologies contribute to shape the glacier piedmont lobe Another possible driver, on long time scales, is active tectonics that can change the topography and change river paths (Carraro & Petrucci, 1977). Sections illustrate the intricate relationships between the different glacial and interglacial units
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