Disentangling the Stratigraphic Architecture of the Rivoli-Avigliana End Moraine System (Western Alps, NW Italy)
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Journal of Maps ISSN: (Print) (Online) Journal homepage: https://www.tandfonline.com/loi/tjom20 Disentangling the stratigraphic architecture of the Rivoli-Avigliana end moraine system (Western Alps, NW Italy) Gianfranco Fioraso, Giovanni Monegato, Gianni Balestro, Irka Hajdas & Paolo Baggio To cite this article: Gianfranco Fioraso, Giovanni Monegato, Gianni Balestro, Irka Hajdas & Paolo Baggio (2021): Disentangling the stratigraphic architecture of the Rivoli-Avigliana end moraine system (Western Alps, NW Italy), Journal of Maps, DOI: 10.1080/17445647.2021.1942252 To link to this article: https://doi.org/10.1080/17445647.2021.1942252 © 2021 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group on behalf of Journal of Maps View supplementary material Published online: 23 Jun 2021. Submit your article to this journal View related articles View Crossmark data Full Terms & Conditions of access and use can be found at https://www.tandfonline.com/action/journalInformation?journalCode=tjom20 JOURNAL OF MAPS https://doi.org/10.1080/17445647.2021.1942252 SCIENCE Disentangling the stratigraphic architecture of the Rivoli-Avigliana end moraine system (Western Alps, NW Italy) Gianfranco Fioraso a, Giovanni Monegato b, Gianni Balestro c, Irka Hajdas d and Paolo Baggioe aInstitute of Geoscience and Earth Resources – National Research Council, Turin, Italy; bInstitute of Geoscience and Earth Resources – National Research Council, Padova, Italy; cDepartment of Earth Sciences, University of Turin, Turin, Italy; dLaboratory of Ion Beam Physics, ETH Zurich, Zurich, Switzerland; eSGB Studio Geologico Baggio, Turin, Italy ABSTRACT ARTICLE HISTORY The Rivoli-Avigliana end moraine system (Italian Western Alps) hosts an important stratigraphic Received 2 February 2021 archive of Pleistocene glaciations. A new geological map provides a 3D architecture of the Revised 2 June 2021 system that reveals a complex architecture of glacial, alluvial and lacustrine units. Six glacial Accepted 4 June 2021 units were recognized. During the deposition of the four older glacial units (Early-Middle ff KEYWORDS Pleistocene) the morphology of the valley outlet had a di erent drainage pattern from the Italian Western Alps; Rivoli- present, with the presence of large lakes. From the penultimate glaciation to the Last Glacial Avigliana end moraine Maximum (LGM) the piedmont lobe was confined within the valley, never extending system; glacigenic deposit; towards the alluvial Po Plain. The LGM is characterized by two glacial advances and four 14C, geomorphology 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. 1. Introduction southern side of the Alps (e.g. Ivrea, Garda, Taglia- The glacial end moraine systems, also called morainic mento), the Rivoli-Avigliana amphitheatre shows an amphitheatres, are characteristic glacial landforms of unusual ‘bullet shape’ instead of the ‘classic’ concentric Alpine valley outlets. They are the result of multiple arcuate pattern. Since the mid-nineteenth century, this advances of glacial piedmont lobes, which spread out end moraine system has been the subject of numerous from the European Alps during the Pleistocene cold stratigraphic and morphological studies (Capeder, periods. Their stratigraphic reconstruction promoted, 1904; Martins & Gastaldi, 1850; Prever, 1907; Sacco, since the late nineteenth century (Gastaldi, 1872), the 1887). Subsequently, the climato-stratigraphic model concept of glaciations and the development of the of Penck and Brückner (1909) was applied to the Riv- fourfold chronostratigraphic subdivision of Penck oli-Avigliana amphitheatre by Sacco (1921), Mattirolo and Brückner (1909). The stratigraphic architecture et al. (1913), Mattirolo et al. (1925), Bortolami et al. of an end moraine system is strongly influenced by (1969) and Petrucci (1970). A complete cartographic the configuration and dynamics of the glacial pied- review was recently carried out by Balestro et al. mont lobe and then of the terminal moraines. The (2009a) in the frame of the CARG Project (National size of the valley glacier, which can be considerably Geological Cartography), mainly based on morphostra- different from one cold phase to another, is the leading tigraphic and pedostratigraphic criteria. Unfortunately, factor for the configuration of terminal moraines. The despite the extensive studies conducted in the past, in shape of the valley outlet, the inheritance of the river the absence of radiometric and subsurface data, the thalweg, and the presence of irregular bedrock mor- age and the stratigraphic relationships of the moraines phologies also contribute to shape the glacier pied- have often remained uncertain and ambiguous. mont lobe. Another possible driver, on long time Thanks to the results of a recent subsoil exploration scales, is active tectonics that can change the topogra- campaign and new radiometric dating, in this paper phy and change river paths (Carraro & Petrucci, 1977). we present a new stratigraphic architecture and a The Rivoli-Avigliana end moraine system, located at more accurate chronostratigraphy of the Rivoli- the outlet of the Susa Valley (Dora Riparia basin) in the Avigliana morainic amphitheatre. Results reported in European Western Alps, is the westernmost of the end Main Map led to reconstruct the different phases of moraine systems that reach the alluvial Po Plain (Figure glacial advances that contributed to form the morainic 1). Unlike other end moraine systems located on the amphitheatre as a whole, while the explanatory cross- CONTACT Gianfranco Fioraso gianfranco.fi[email protected] Supplemental data for this article can be accessed here https://doi.org/10.1080/17445647.2021.1942252. © 2021 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group on behalf of Journal of Maps This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrest- ricted use, distribution, and reproduction in any medium, provided the original work is properly cited. 2 G. FIORASO ET AL. Figure 1. Geomorphological scheme of the Western Po Plain (modified from Piana et al., 2017a). sections illustrate the intricate relationships between geomorphological features such as moraine ridges, the different glacial and interglacial units. erosional scarps, traces of abandoned river channels are shown in the Main Map. Particular attention was paid to the mapping of erratic boulders, often the 2. Methods only elements capable of attesting the outermost gla- The Main Map, designed to be at a scale of 1:25,000, cier terminal position in the lowland area. encompassesanareaof291km2 between the Graian Although exposures are rare, to define the end mor- and Cottian Alps, at the mouth of the Susa Valley in aine system architecture and the relationships with the the Western Po Plain (Figure 1). Detailed geological pre-glacial successions (illustrated in 6 geological data and geomorphological features were collected cross-sections at a 1:5 h/v scale 1:25,000/1:5,000), by original mapping performed at a scale of 253 logs of boreholes (177) and water wells (76) up 1:10,000. Field work was integrated with stereoscopic to 270 m deep, were collected from the geotechnical photo interpretation of multi-temporal aerial database of the Regional Agency for the Protection images. of the Environment (ARPA Piemonte), from the In addition to bedrock geology and glacial, gla- CARG Project and from other technical reports and ciofluvial, alluvial and slope deposits, some indicated in the Main Map. JOURNAL OF MAPS 3 Table 1. 14C data in the Rivoli-Avigliana end moraine system (previous Authors). Depth Cal. age 95% of probability Code Locality (m) Material Age (y BP) (y BP) Reference C1 LTL12084A outcrop charcoal >45,000 >45,000 Ivy-Ochs et al. (2018) C2 Villar Dora 3 wood fragment of 10,000 ± 75 11,805–11,253 Charrier and Peretti, (1973, 1975) pine C3 Novaretto 4 peat layer 7,780 ± 100 8980–8385 Charrier and Peretti (1975) C4 Lago 1.75 gyttja 1,565 ± 43 1532–1364 Larocque and Finsinger (2008) Finsinger and Piccolo Tinner (2006) C4-5 Lago 9.09 gyttja 14,930 ± 80 18,619–18,049 Larocque and Finsinger (2008) Piccolo Finsinger and Tinner (2006) Stratigraphic analysis of recent core samples elevation of 315 m at the Alpignano gorge. Mean (1020 m total core length) obtained from 20 drillings elevation of the catchment is 1709 m. The trunk valley made it possible to collect some samples of organic extends west–east for about 83 km. After exiting the matter for radiocarbon dating, which allowed for the Alpignano gorge, the river cuts the outwash plain to definition of the chronostratigraphy of the Last Glacial join the Po River in the city of Turin, at 210 m a.s.l. Maximum (LGM) moraines and the withdrawal Along the drainage divide, some prominent mor- phases of the glacial front. phological saddles, mainly induced by glacial erosion, To better understand the dynamics of the Dora are present: from north to south the Moncenisio Riparia glacier in the frame of the Northern Cottian (2081 m), Piccolo Moncenisio (2183 m), Thures Alps, the scheme of the ice flow pattern has been (2194 m), Scala (1762 m), Monginevro (1850 m), inserted in the Main Map. Bousson (2154 m), Chabaud (2213 m) and Sestriere Field data are represented on a vector topographic