Gianotti, F.

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UNIVERSITÀ DEGLI STUDI DI TORINO DIPARTIMENTO DI SCIENZE DELLA TERRATHE END-MORAINE SYSTEM OF THE PLEISTOCENE MOLETTA GLACIER (SUSA VALLEY, NW, ITALY)CRETÌ E. 1* , GIANOTTI F. 11 EARTH SCIENCES DEPARTMENT, UNIVERSITY OF TORINO, TORINO, ITALY(edoardo.creti@edu.unito.it, franco.gianotti@unito.it)Some elongated reliefs with a moraine-like morphology have been found on the valley side laterally to the deep incision of the Rio Moletta; Most of them are N-S oriented (i.e. parallel to the Rio Moletta incision), while three of them are cur---7. BIBLIOGRAPHY Cadoppi, P., Castelletto, M., Sacchi, R., Baggio, P., Carraro, F., & Gi -raud, V. (2002). Note illustrative della Carta Geologica d’Italia alla sca-la 1:50.000 – Foglio 154, Susa. Roma: Servizio Geologico d’Italia, p. 127.Cretì E. (2019) – Rilevamento geologico dell’apparato morenico termina-le del ghiacciaio pleistocenico di Moletta a nord di Bussoleno (Val di Susa). Ined. Gasco I., Gattiglio M., Borghi A. (2011) - Lithostratigraphic setting and P-T metamor-phic evolution for the Dora-Maira Massif along the Piedmont Zone boundary (mid-dle Susa Valley, NW Alps). Int. J. Earth Sci. (Geol. Rundsch), 100, 5, pp. 1065-1085.Ivy-Ochs S., Lucchesi S., Baggio P., Fioraso G., Gianotti F., Monegato G., Graf A., Akçar N., Christl M., Carraro F., Forno M.G. & Schlüchter C. (2018) - New geomorphological and chro-nological constraints for glacial deposits in the Rivoli-Avigliana end-moraine system and the lower Susa Valley (Western Alps, NW Italy). Journal of Quaternary Sciences, 33 (5), 550-562.Polino R., Malusà M., Morelli M. & Piana F. (2002). - Correlabilità tra dato satellitare e -ta valle d’aosta. Cinematiche Collisionali: tra esumazione e sedimentazione; 81a Riunio-ne estiva della Società Geologica Italiana Torino, 10-12 settembre 2002, p. 219-220.Sacco F. (1887) -  Boll. R. Comit. Geol. It., 5-6, 45 pp.Carta Geologica del settore di sbocco del Rio Moletta (Bussoleno, Valle di Susa)scala 1:5000DCasa SchiariS. LorenzoComba delle FoglieBC SBGFBCS(Aff. = affioramento)Depositi di till di colata di margine glacialeAff.Depositi di delta-conoide glaciolacustri di margine glacialeAff.f.Till subglacialeAff.Aff.Successione glacigenica(Pleistocene sup. - Tardoglaciale)Unità Dora MairaSubstrato RocciosoGneiss Quarziti Micascisti Marmi e metadolomie Depositi detritico-colluvialiDepositi di debris-flowDepositi fluvialiDepositi detritici di faldaSuccessione postglacialeOlocene - AttualeCopertura QuaternariaEdoardo Cretì (2020) - Rilevamento geologico dell’apparato morenico terminaledel ghiacciaio pleistocenico di Moletta a nord di Bussoleno (Val di Susa).Tesi di Laurea Triennale in Scienze Geologiche, Università degli Studi di TorinoSimboliOrlo di scarpata fluvialeCresta di morena non evidenteCresta di morenaOrlo di scarpata#0 Masso erratico > 1 m#* Masso erratico < 1 mBGF= Blocco di gneiss fengiticoBCS= Blocco di calcescistoDStrie Glacialic Fungo d'erosionel Sfioratore glaciale2. GEOLOGICAL SETTING2.1 Bedrock -ropean continental crust units, on the other hand, are divided into: Upper Penninic nappes, formed by subducted continental crust units and including the Inner Crystalline Massifs (Dora Maira, Gran Paradiso and Monte Rosa); Intermediate Penninic nappes, consisting of the Gran San Bernardo Nappe and the Sub-Brian--consists of oceanic crust made of serpentinite and prasinite (Piemontese Zone), oucropping in the upper sector of the valley and tectonically overlying (car-gneule) on a continental crust made of paragneiss, micaschist and dolomite marble (Dora Maira Massif) outcropping in the lower sector (Cadoppi et al., 2002).1. INTRODUCTIONof this catchment (1450 m with a maximum at 3619 m a.s.l. at Punta Roncia) and many plateaux up to 3000 m a.s.l. allowed the development of a 90 km -A new geological survey (Cretì, 2019) was so carried out north of Bussoleno at the outlet of the Moletta Valley, with the aim of check in more detail the relationship between the tributary Moletta Glacier and the main Dora Riparia Glacier in the Last Glaciation. 4. STRATIGRAPHY-red on the trunk valley side, rest above the subglacial till and are referred mainly to the trunk glacier. Some geomorphological elements have been found on the valley side at the edges of the lower T. Moletta incision (a latero-frontal moraine en-are interpreted as the remnants of an end-moraine system largely buried under the alluvial fan deposits and referred to the Moletta Glacier. 4.1 Lodgement till and subglacial melt-out till-----trographic composition is in agreement with a supply from the Rio Moletta basin. Layers with coarse matrix are weakly cemented .-cation and the low degree of over-consolidation specify the facies as a subglacial/submarginal melt-out till. Fig. 1 – Rio Moletta basin (red box) north of the town of Bussoleno, Susa Valley.Fig. 2 – Susa Sheet (154) of the Geological Map of Italy, detail of the Bussoleno area and Rio Moletta valley (from Cadoppi et al., 2002). Calcescist with marble levels (CTM), serpentinite and serpentinoscist (OSS), dolomitic marble (PMC), calcescist (MCF), gray-blue marble (MGZ), meta-dolomite (MMD), “Pietra di Luserna” gneiss (DLG ), Polymetamorphic Complex (DMS).2.2 Quaternary coverage-nal forms and in the locally well preserved glacigenic deposits and forms, present on both sides of the valley. reach of the Susa Valley has been investigated for the geological survey of two geological sheets of the new Italian Geological Map at the scale -2009), two related to the Middle Pleistocene glacial expansions (S. Gillio synthem and Bennale synthem) and three related to the Late Pleisto-traced along the lower reach of the valley (Cadoppi et al., 2002), where moraines and kame terraces are discontinuosly spread on both sides. More recently, the surface exposure dating method on erratic boulders from the lower reach of Susa Valley to the Rivoli-Avigliana terminal moraines has dated the LGM maximum glacier advance at 24.0±1.8 ka (Ivy-Ochs et al., 2018), in-phase to the Alpine LGM reconstructed in other sectors.In the Susa valley section, however, only the deposits and forms related to the phase of maximum expansion of the last glaciation (LGM, 29-19 ka BP) and its withdrawal phases (Lateglacial, 19-11.7 ka BP) are evident, with the excep-tion of the traces of the penultimate glacial expansion preserved only in the sector close to the valley outlet.In the study area north of Bussoleno, the various sedimentary bodies present on the lower slope around  the Moletta incision outlet have been inter-600-800 m a.s.l.) all the glacigenic deposits would correspond to glacio-lacustrine sediments referable to the main glacier (in this case to the Ceni-3. METHODS- ,)2002 ,.lateippodaC(00005 :1 elac eht t ylatI f paM lacigoloeG ht fo teeh asuS-451 eht yllaieps ,detlusno dn denimax sa skro suoirP v we w e a c e c S e o a s-cal analysis (plano-altimetric location and orientation of the depositional and erosional forms) and the petrographic composition of clasts (presen--ble with a saccharoid aspect associated with tectonic breaches (PMC; Mesozoic cover of the Dora-Maira Unit). Considering the main basin (Susa Valley-Cenischia Valley), albitic-gneisses, micaschists and paragneisses that form intercalations within the calcescists (Puys-Venaus tectonometa-morphic unit), the prasinitic and prasinite-gneisses, amphibolytic and chloritoscist schists and to the, massive and listed prasinites, actinolytic am-phibolites and chloritoscists (lower Susa Valley – Lanzo Valley - Monte Orsiera tectonometamorphic unit) are the more useful marker lithologies.Topographic base was taken from the “BDTRE - Territorial Reference Data Bank of Bodies”, with equidistance of 10 m between the contour lines, downloaded from the Geoportal of the Piedmont Region and reproduced at a scale of 1: 10000. DTM and Google Earth maps were also used.--ries of ice-marginal lakes formed in ephemeral depression  on the valley slope dammed by the two glaciers, and  A greater expansion of the tributary glacier is therefore recognized and reported on a new geological map com-pared to the previous extent reported in the Susa Sheet of the Geological Map of Italy (Cadoppi et al., 2002).identified in  the  context   of   the   generalized  glacial  retreat  that  occurred  in  the   Lateglacial (19-11.7 ka BP).  In  particular,   the  withdrawal presence of more lateral moraines   on   the    main    slope   on  both   sides    of    the    tributary     incision    has  been    ascertained,   but    the   reco-With the complete withdrawal of the trunk glacier, the Moletta Glacier expanded on the fan sec-tor at least up to an altitude of 482 m a.s.l. and 350 m away downstream of the valley mouth. -refore with unfavorable southern exposure of the basin. . Despite a generalized reduction in volume of all glaciers during Late-of these basins, their high accumulation/ablation area ratio  and the short distances between glacial cirques and valley outlets. -tary Moletta Glacier and the Dora Riparia Glacier, which integrate the knowledge on the glacialism of the Susa Valley. Fig. 3 – Subglacial melt-out till (outcrop located 10 m north of “Casa Schiari” at 560 m a.s.l.).Fig. 5 – View of a lateral right moraine of the Moletta Glacier (NW of Casa Schiari at 600 m a.s.l.) Fig. 6 – N-S oriented glacial striae on a roche moutonnée of meta-dolomites (north of Casa Schiari at 570 m a.s.l.)4)  in the upper sector of the Rio Moletta allu--gular and smoothed and are made of serpentinite and serpentinoscist and rare gneiss and calcschist up to 2 m in size, and form elongated ridges . Overall, a weakly arched accumulation with an E-W trending as the coarse remain of a previous end-moraine totally demolished by the T. Moletta erosional activity.-over time thanks to the weakly cementation of the deposits (Fig. 4). However, their morphological expression (kame terraces) is not preserved.Fig. 7 – Erratic boulder of serpentinite 2x3x2 m sized lying on the proximal sector of the Rio Moletta alluvial fan at 510 m a.s.l.Fig. 4 – Glaciotectonically faulted ice-marginal glaciolacustrine deposits with a gently dipping planar-cross and plano-parallel bedding, cemented, ( road to Falcimagna at 735 m a.s.l.).5. EVIDENCES OF THE TRIBUTARY MOLETTA GLA-CIER ADVANCE IN THE DORA RIPARIA VALLEY FLOORSome geomorphological elements have been found on the valley side at the edges of the lower T. -ding glacial-striae on roche moutonnée) and in the apex sector of the T. Moletta alluvial fan (a set of transversal scarps not due to river erosion; a cluster of 1-2 long serpentinite blocks; a big ser--ne system largely buried under the alluvial fan deposits and referred to the Moletta Glacier. 1) A --2) (Fig. 6)  on a roche moutonnée of meta-dolomites north of Casa -ta Glacier and constitutes further evidence of the tributary glacier advance at a very low altitude.3)  on the alluvial fan with anomalous trending becau-on the continuation of the moraine and can be interpreted as the morphological eviden-ce of one or two frontal moraines almost completely buried under the alluvial deposits. Fig. 8a – Moletta Glacier joined the Dora Riparia Glacier during the Last Glacial Maximum; in ephemeral depression  on the valley slope dammed by the two glaciers                                                                                                                                                                                                                                                                                        Fig. 8c - Moletta Glacier reached a b c6. RESULTS5) A little further upstream, the presence of a about 15 m sized block of serpentinite on the al -luvial fan surface is a fundamental element for our reconstruction. It constitutes a typical -(Fig. 7)  and so it is proof of the arrival of the glacial front at least up to this point.3gnition   of   a   end-moraine   apparatus  in Balestro G.,  Cadoppi P.,  Piccardo G.B.,  Polino R.,  Spagnoli G.,  Tallone S., Fioraso G., Lucchesi S., Forno M.G. (2009) -                                                                                                   Servizio Geologico d'Italia, p. 150. Note illustrative della Carta Geologica d’Italia alla sca -la 1:50.000 – Foglio 155, Torino Ovest.vergenceof  the  Dora  Riparia

The end-moraine system of the Pleistocene Moletta Glacier (Susa Valley, NW Italy)

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The end-moraine system of the Pleistocene Moletta Glacier (Susa Valley, NW Italy)

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