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Timing of LGM and deglaciation in the Southern Swiss Alps

Chronologie du DMG (Dernier Maximum Glaciaire) et de la déglaciation dans les Alpes Suisses Méridionales
Cristian Scapozza, Claudio Castelletti, Linda Soma, Stephan Dall’Agnolo et Christian Ambrosi
p. 307-322

Résumés

La cartographie géologique minutieuse des terrains du Quaternaire dans la Suisse méridionale (Mendrisiotto et régions italiennes environnantes) et la compilation de plusieurs datations radiocarbone ont permis de reconstituer la géométrie et la chronologie du Dernier Maximum Glaciaire (DMG/LGM) dans le Sud des Alpes Suisses. Ces résultats ont aussi permis d’obtenir une chronostratigraphie détaillée des principaux stades glaciaires qui ont marqué le Tardiglaciaire et le début de l’Holocène. Les stades glaciaires définis ont été corrélés aux évènements de l’enregistrement isotopique du sondage NGRIP au Groënland. L’analyse des âges radiocarbone calibrés maximaux et minimaux du DMG permet de placer cet épisode entre 28500 et 22900 cal BP (24500-19000 14C BP). L’avancée glaciaire attribuée au DMG a donc été corrélée de manière hypothétique avec le GS-3, compris entre 27400 et 22700 cal BP. Pour le Pléniglaciaire et la transition Pléniglaciaire/Tardiglaciaire, les premières phases de régression glaciaire après le DMG ont été placées entre ca. 22500 et 21000 cal BP, et peuvent correspondre aux deux premiers épisodes froids du GS-2c. Le premier stade du Tardiglaciaire a été le stade de Melide, qui peut correspondre avec l’un des deux épisodes froids de 20450 ou 19850 cal BP. Par la suite, dans les vallées de Leventina et de Bedretto (glacier du Ticino), cinq stades glaciaires ont été mis en évidence pour le Dryas ancien (stades de Biasca, Faido, Airolo, Fontana et All’Acqua), deux pour le Dryas récent (Maniò et Alpe di Cruina) et un (Val Corno), en correspondance avec l’épisode froid holocène du Groënland GH-11.2.

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Notes de la rédaction

Article soumis 14 janvier 2014, accepté le 24 juin 2014.

Texte intégral

A special thanks to the associate editor, Prof. Dr. Margot Böse, and to the two anonymous reviewers for their useful feedback, as well as Jan Hardie for proofreading the English.

Introduction

1Following the pioneering work by A. Penck and E. Brückner (1901-1909), many studies have focused on piedmont glacier extension and on the history of the last deglaciation in the European Alps, during Quaternary. In the course of the last century, there have been considerable developments in the level of understanding regarding the morphostratigraphical sequence of deglaciation during the Lateglacial. The scheme developed by A. Penck and E. Brückner (1909) contained only three glacial stadials (Bühl, Gschnitz and Daun), but at the beginning of the 1980s six stadials were identified in different regions of the Alps (Müller et al., 1980; Maisch, 1982; Schoeneich et al., 1997; Coutterand and Nicoud, 2005). Thanks to the application of surface exposure-dating with cosmogenic nuclides, the chronology of the last glacial cycle was significantly improved, particularly in the Eastern Alps (e.g., Ivy-Ochs et al. 2007; Reitner, 2007; Ivy-Ochs et al., 2008, and references therein).

2However, the evolution and chronology of Quaternary glaciations in the Southern Swiss Alps were often considered as different from those in the Northern or Eastern Alps (Bini, 1997; Bini et al., 2009), and the southern face of the Alps was omitted from overviews of the Swiss Alps deglaciation (Schlüchter, 1988; Schoeneich, 1998; Ivy-Ochs et al., 2008). Presented here is a reassessment of deglaciation timing based on a compilation and re-evaluation of existent radiocarbon dates.

3This revision of the LGM chronology and of the last deglaciation in the Southern Swiss Alps was conducted during the realisation of the 1:25,000 Quaternary geological map of Sheet 1373/Mendrisio (Ambrosi et al., 2014), covering the southern part of Canton Ticino and the northern part of Italy, between Como and Varese (fig. 1).

Fig. 1 – Localisation of the study area, representation of the glacial extent during the LGM and position of the discovered organic material supplying the radiocarbon dating presented in tab. 1 and in fig. 2A.
Fig. 1 – Localisation du secteur étudié, représentation de l’extension glaciaire pendant le DMG et position des découvertes de matériel organique ayant permis les datations radiocarbone présentées dans le tab. 1 et dans la fig. 2A.

Fig. 1 – Localisation of the study area, representation of the glacial extent during the LGM and position of the discovered organic material supplying the radiocarbon dating presented in tab. 1 and in fig. 2A. Fig. 1 – Localisation du secteur étudié, représentation de l’extension glaciaire pendant le DMG et position des découvertes de matériel organique ayant permis les datations radiocarbone présentées dans le tab. 1 et dans la fig. 2A.

The radiocarbon dating number corresponds to the numbers in the first column of tab. 1. The positions of dating rd-1, rd-4, rd-7, rd-11 and rd-13 are not represented because they lie outside of the map frame. 1: main pass; 2: radiocarbon dating; 3: Faloppia sub-lobe. Equidistance of the contour lines: 200 m.
L'identifiant de la datation radiocarbone correspond à l'identifiant de la première colonne de la tab. 1. La position des datations rd-1, rd-4, rd-7, rd-11 et rd-13 n’est pas représentée parce qu’elle se situe en dehors du cadre de la carte. 1 : col principal ; 2 : datation radiocarbone ; 3 : sous-lobe de la Faloppia. Equidistance des courbes de niveau : 200 m.

Modified from Bini et al., 2009.
Modifié d’après Bini et al., 2009.

4Detailed mapping of the glacial and glaciofluvial deposits and landforms, and the compilation of several radiocarbon dates for the Ticino and Adda glaciers, makes it possible to establish the extent and chronology of the Last Glacial Maximum (LGM) in the Southern Swiss Alps. Moreover, the calibration of radiocarbon dates, together with the glacial recessional stadials specified in the literature, can be used to obtain a detailed chronostratigraphy of the main recessional stadials during the Lateglacial and at the beginning of the Holocene. The chronological assessment of the deglaciation, and the definition of the Equilibrium Line Altitude (ELA) depression, makes it possible to attempt to correlate the glacial stadials defined in the Ticino Valley with the Eastern Alps model. This assessment means that climatic fluctuations indicated by the glacial stadials can therefore be correlated with the NGRIP Greenland isotopic record (North Greenland Ice Core Project; NGRIP-Members, 2004a).

Methods

Radiocarbon dating compilation and calibration

526 radiocarbon dates generated from Ticino (Switzerland) and Lombardy (Italy) were compiled from previous works (tab. 1), and plotted in a graph in accordance with the time period covered for every date, and with their respective positions in the morphostratigraphy of the glacial deposits of the Ticino and Adda glaciers, from the Po plain to the higher part of the Bedretto Valley (fig. 2A).

Tab. 1 – Compilation of radiocarbon dating, making it possible to reconstruct the deglaciation in the Southern Swiss Alps.

Tab. 1 – Compilation des datations radiocarbone permettant la reconstitution de la déglaciation du Sud des Alpes Suisses.

Sample ID

Laboratory code

Code de laboratoire

Locality

Localité

Material

Matériel

Age 14C BP

Age cal BP

Source

rd-1

GX-16,079

Valle della Calcina (VA)

Wood / Bois

> 35,200

> 40,060

1, 2

rd-2

GX-15,512

Fino Mornasco (CO)

Palaeosoil / Paléosol

> 32,300

> 36,395

1, 2

rd-3

UZ-2,680/ETH-7,378

Morbio superiore

Wood / Bois

32,940 ± 540

38,535 – 35,900

2, 3

rd-4

GX-16,077

Castelnovate (Vizzola Ticino, VA)

Palaeosoil / Paléosol

32,200 ± 2000

42,290 – 32,990

1, 2, 4

rd-5

GX-16,080

Albusciago (Sumirago, VA)

Palaeosoil / Paléosol

31,515 ± 1850

41,360 – 32,385

1, 2, 4

rd-6

UZ-2,745/ETH8,700

Morbio Inferiore

Wood / Bois

31,180 ± 640

36,995 – 33,970

2, 3

rd-7

GX-14,749

Valle del Seveso (MB)

Palustrine deposits / Dépôts palustres

> 28,500

> 32,870

1, 2

rd-8

UZ-2,569/ETH-5,920

Cernobbio (CO)

Wood / Bois

28,420 ± 570

33,685 – 31'295

2, 5

rd-9

UZ-2,744/ETH-8,699

Morbio Inferiore

Wood / Bois

28,140 ± 450

33,270 – 31'205

2, 3

rd-10

GX-15,513

Fino Mornasco (CO)

Palaeosoil / Paléosol

27,200 ± 2250

40,385 – 28'435

1, 2

rd-11

GX-16,078

Castelnovate (Vizzola Ticino, VA)

Palaeosoil / Paléosol

26,500 ± 1000

33,080 – 28'690

1, 2, 4

rd-12

GX-14,748

Fino Mornasco (CO)

Palaeosoil / Paléosol

18,430 ± 300

22,900 – 21'575

1, 2

rd-13

R-801α

Pontida (BG)

Branches, leafs and seeds /

Branches, feuilles et grains

17,700 ± 360

22,335 – 20'565

6, 7, 8, 9, 10

rd-14

GrA-29,436

Via Valleggio (Como)

Organic material / Matériel organique

13,880 ± 200

17,425 – 16,245

11

rd-15

GrA-23,357

S. Abbondio (Como)

Wood / Bois

13,230 ± 120

16,260 – 15,495

11

rd-16

B-2,997

Biandronno (VA)

Wood / Bois

13,290 ± 100

16,270 – 15,685

10, 12, 13

rd-17

ETH-495

Bissone

Wood and seeds / Bois et grains

13,070 ± 165

16,135 – 15,185

14

rd-18

B-874

Suossa (San Bernardino)

Gyttja / Gyttja

13,010 ± 200

16,205 – 15,000

15,16

rd-19

Müller-1972 (code not found)

Vall’Ambrosa (Campra)

Peat / Tourbe

12,890 ± 160

15,950 – 14,880

17

rd-20

UZ-5,199/ETH-30,382

Mondascia (Biasca)

Wood / Bois

12,370 ± 85

14,900 – 14,085

18

rd-21

B-2,849

Bedrina (Dalpe)

Gyttja / Gyttja

12,170 ± 110

14,545 – 13,745

19

rd-22

LHGI*

S. Abbondio (Como)

Wood / Bois

11,730 ± 180

14,005 – 13,210

11, 20

rd-23

UZ-4,722/ETH-25,355

(Lavorgo, Faido)

Wood / Bois

11,690 ± 85

13,735 – 13,350

21

rd-24

UZ-167

Plidutscha

Gyttja / Gyttja

10,325 ± 130

12,575 – 11,620

22, 23

rd-25

UZ-348

Val Torta

Peat / Tourbe

9,995 ± 110

11,960 – 11,220

22, 23

rd-26

UZ-222

Alpe di Cruina

Peat / Tourbe

6,370 ± 85

7,460 – 7,025

22, 23

*LHGI = Laboratoire d'Hydrologie et de Géochimie Isotopique, Université Paris-Sud.
1: Bini (1997); 2: Bini et al. (2001); 3: Felber (1993); 4: Da Rold (1990); 5: Rossi et al. (1991); 6: Alessio et al. (1975); 7: Alessio et al. (1978); 8: Orombelli (1974); 9: Orombelli (1983a); 10: Orombelli (1983b); 11: Comerci et al. (2007); 12: Schneider (1978); 13: Porter and Orombelli (1982); 14: Niessen and Kelts (1989); 15: Oeschger et al. (1970); 16: Zoller and Kleiber (1971); 17: Müller (1972); 18: Scapozza et al. (2012); 19: Küttel (1977); 20: Castelletti and Orombelli (1986); 21: Antognini and Volpers (2002); 22: Renner (1982); 23: Keller (1988b).
Pour les sources, voir la légende anglaise.

Fig. 2 – Correlation of the main deglaciation stadials in the Southern Swiss Alps with the Greenland isotopic stratigraphy.
Fig. 2 – Corrélation des principaux stades de déglaciation du Sud des Alpes Suisses avec la stratigraphie isotopique du Groenland.

Fig. 2 – Correlation of the main deglaciation stadials in the Southern Swiss Alps with the Greenland isotopic stratigraphy. Fig. 2 – Corrélation des principaux stades de déglaciation du Sud des Alpes Suisses avec la stratigraphie isotopique du Groenland.

A: Box plot of the radiocarbon dates compiled in tab. 1. 1: organic material within the tills of the Episodio Cantù (= minimum age of the LGM and minimum deglaciation age of the Como area, Mendrisiotto and lower Lake Verbano); 2: sediments buried by lodgement till of the Episodio Cantù (= LGM) and palaeosoils of the Allogruppo di Besnate (precedent the Episodio Cantù); GL-2: radiocarbon dating of the P-level on a geomagnetical profile. B: Correlation hypothesis between the LGM and the main Lateglacial stadials of the Ticino/Adda glaciers, and the Eastern Alps analogues and with the isotope stratigraphy of the Greenland ice core NGRIP (numerical data from NGRIP-Members, 2004b).
A : Graphique des datations radiocarbone compilées dans le tab. 1. 1 : matériel organique dans les tills de l’Episodio Cantù (= âge minimal du DMG et de la déglaciation de la zone de Como, du Mendrisiotto et du bas Lac Verbano) ; 2 : sédiments enterrés par les tills de fond de l’Episodio Cantù (=DMG) et paléosols de l’Allogruppo di Besnate (précédant l’Episodio Cantù) ; GL-2: Datation radiocarbone du niveau P dans un profil géomagnétique. B : Hypothèses de corrélation du DMG et des principaux stades tardiglaciaires des glaciers du Ticino et de l’Adda avec les analogues des Alpes Orientales et avec la stratigraphie isotopique groenlandaise du forage NGRIP (données numériques d’après NGRIP-Members, 2004b).

6All the radiocarbon dates reported here were calibrated using OxCal 4.2 software (Bronk Ramsey, 2001, 2014), in accordance with the IntCal13 calibration curve (Reimer et al., 2013), and with a 2σ confidence interval (95.4% probability). The calibrated dates are expressed in calendar years before present (cal BP), while the conventional ages are expressed in radiocarbon years before present (14C BP) (Miallier and Lefèvre, 2013), with the present corresponding to ad 1950.

Morphostratigraphy of the glacial stadials

7The morphostratigraphy of deglaciation is based on the definition of the former-ELA, with the ELA depression calculated from a reference altitude. The ELA was calculated using the Accumulation Area Ratio (AAR) hypsometric method, based on 0.67 ratio for the accumulation surface/total surface of a glacier (Kerschner, 1976; Gross et al., 1977), corresponding to a ratio of 2:1 between the accumulation surface and the ablation surface of a glacier. The ELA depression was calculated on the basis of the difference in altitude between the former-ELA and the ELA calculated for the end of the Little Ice Age (1850/60 AD in the Central and Southern Swiss Alps), considered as the last important glacial stadial with the glaciers in a condition of climatic equilibrium (Dorthe-Monachon and Schoeneich, 1993).

Greenland isotope stratigraphy

8The general climatic framework for the northern hemisphere is supplied by the oceanic and Greenland isotope curves, which make it possible to establish the volumetric variations in the continental ice sheets, and the air temperature variations in the northern Atlantic (Johnsen et al., 2001). Since the Alps contributed relatively little to the global ice masses during past glaciations, a more detailed climatic proxy is supplied by the Greenland isotopic stratigraphy. Variations in δ18O reflect variations in temperature and in the circulation of moisture. More negative δ18O values reflect colder air temperatures, and more positive δ18O values therefore reflect warmer air temperatures. A δ18O value is based on the difference (in ‰) between the isotopic ratio of the oxygen contained in the ice (18O/16O ratio or Ri = ice ratio) and the isotopic ratio of a reference standard (Rs = standard ratio):

9δ18O = [(Ri – Rs) / Rs] * 1,000 (1)

10In accordance with the variations of δ18O, it is possible to define several Greenland Isotope Stages (GIS), including cold stadials (GS) and interstadials (GI) for the Pleistocene, and the main Holocene cold events (GH), in line with the INTIMATE stratigraphy (INTegration of Ice core, Marine and TErrestrial records of the last termination; Blockley et al., 2012).

11It is cleat that the proposed correlations between Greenland stadial and glacial advances in the Alps are highly speculative, since high levels of dating uncertainty do not permit safe correlations (e.g., Blaauw et al., 2010). In particular, it is not possible to determine the impact of (winter) air temperature over Greenland on the accumulation balance of glaciers, which is mainly governed by summer temperature and winter precipitation, particularly for the southern side of the Alps.

Regional setting

LGM in the Southern Swiss Alps

12In the Southern Swiss Alps, the equivalent of the LGM extent as defined by A. Bini (1997) has been named Episodio Cantù and corresponds to the paroxistic phase of the last glaciation, known as Glaciazione Cantù in the regional allostratigraphy (Bini, 1987; Felber, 1993; Bini et al., 2001). The deposits related to this glaciation are grouped in the Alloformazione di Cantù, corresponding to the Alloformazione di Bodio as defined by O. Da Rold (1990), and includes weakly weathered glacial, glaciofluvial, deltaic, lacustrine and glaciolacustrine deposits, with well-preserved morphology, without loess cover, and very locally cemented. During the LGM advance, the Ticino and Adda glaciers reached a limited extension compared to the previous glaciations (in particular, the Glaciazione Daverio preceding the Glaciazione Cantù). The Verbano lobe of the Ticino glacier occupies only half of Lake Varese and its front was positioned upslope of Sesto Calende. The Ceresio lobe reached Varese by means of the Porto Ceresio diffluence, and Stabio (in confluence with the Adda glacier) by means of the Capolago diffluence, whereas the Lario lobe of the Adda glacier reached the Como-Chiasso region (Bini et al., 2009; fig. 1).

13In the Mendrisiotto and Luganese areas (southern part of Canton Ticino), during the Pleniglacial the front of the Ticino and Adda glaciers underwent several oscillations that lead to the deposition of numerous moraines located inside the LGM advance moraine complex (fig. 3). These glacial fluctuations were studied and grouped by M. Felber (1993), and later by A. Bini et al. (2001), in the Rancate-Casate-Cucciago and in the Capolago-Roncaccio-Ca’Morta phases. These phases and the followings recessional stadials are listed in Figure 2B.

Fig. 3 – First deglaciation phases following the LGM advance: example of the Faloppia sub-lobe of the Adda glacier in the Chiasso region.
Fig. 3 – Premières phases de la déglaciation suivant le DMG : exemple du sous-lobe de la Faloppia du glacier de l’Adda dans la région de Chiasso.

Fig. 3 – First deglaciation phases following the LGM advance: example of the Faloppia sub-lobe of the Adda glacier in the Chiasso region. Fig. 3 – Premières phases de la déglaciation suivant le DMG : exemple du sous-lobe de la Faloppia du glacier de l’Adda dans la région de Chiasso.

A: Simplified Quaternary geological map. 1: moraine ridge; 2: kame terrace; 3: moraine ridge number. Coordinates: Swiss Grid system CH1903 / LV03. B: Synthetic sketch of the deglaciation of the Faloppia sub-lobe, based on the glacial positions determined by the progression or main stagnation moraines (the numerical code of the moraine ridges refers to the enumeration reported in A). 1: glacial position; 2: kame terrace; 3: important glacial recession. C: Essay of correlation between the Faloppia sub-lobe deglaciation and the isotope stratigraphy of the Greenland ice core NGRIP.
A : Carte géologique simplifiée du Quaternaire. 1 : cordon morainique ; 2 : terrasse de kame ; 3 : numéro du cordon morainique. Coordonnées : système suisse CH1903 / LV03. B : Schéma de synthèse de la déglaciation du sous-lobe de la Faloppia basée sur les positions glaciaires déterminées grâce aux principaux cordons morainiques de progression ou de stagnation (le code numérique des cordons morainiques fait référence à l’énumération reportée en A). 1 : position glaciaire ; 2 : terrasse de kame ; 3 : régression glaciaire importante. C : Essai de corrélation de la déglaciation du sous-lobe de la Faloppia avec la stratigraphie isotopique groenlandaise du forage NGRIP.

Numerical data from NGRIP-Members, 2004b.
Données numériques d’après NGRIP-Members, 2004b.

Reference stadials for the Ticino glacier

14The first well-defined stadial following the deglaciation of the Mendrisiotto corresponds to the Melide stadial as defined on the Ceresio lobe of the Ticino/Adda glaciers, characterised by the lacustrine moraines between Melide and Bissone (Niessen and Kelts, 1989). On the Verbano lobe of the Ticino glacier, R. Hantke (1983) described the Cugnasco stadial as defined by lateral moraines located above Progero on the right side of the valley, and above Cadenazzo on the left side (see Bächlin et al., 1974). According to C. Scapozza et al. (2012), during the Cugnasco stadial, the Ticino glacier front constituted a calving glacier on the Lake Verbano (fig. 4).

Fig. 4 – Palaeogeography of the lower Ticino Valley at the beginning of the Lateglacial during the Cugnasco stadial.
Fig. 4 – Paléogéographie de la partie basse de la Vallée du Ticino au début du Tardiglaciaire pendant le stade de Cugnasco.

Fig. 4 – Palaeogeography of the lower Ticino Valley at the beginning of the Lateglacial during the Cugnasco stadial. Fig. 4 – Paléogéographie de la partie basse de la Vallée du Ticino au début du Tardiglaciaire pendant le stade de Cugnasco.

1: moraine ridge; 2: Ticino glacier; 3: palaeo Verbano Lake; 4: iceberg.
1 : cordon morainique ; 2 : glacier du Ticino ; 3 : paléo Lac Verbano ; 4 : iceberg.

Modified from C. Scapozza et al. (2012).
Modifié d’après Scapozza et al. (2012).

15The mean level of the lake lay between 215 and 220 m asl (today it lies at 193 m asl), corresponding to the maximum level reached at the beginning of the deglaciation because it was controlled by the elevation of the moraines situated north of Sesto Calende (Felber, 2000; Scapozza et al., 2012).

16The compilation of the glacial stadials defined by F. Renner (1982) in the Leventina and Bedretto Valleys, and the definition of the analogues for the Blenio Valley by C. Scapozza and G. Fontana (2009), make it possible to identify nine main glacial stadials following the Cugnasco stadial and located upslope of Biasca (tab. 2).

Tab. 2 – Definition of the reference values of the ELA depression for the Ticino and Brenno glaciers during the Lateglacial.
Tab. 2 – Définition des valeurs de référence de la dépression de la LEG pour les glaciers du Ticino et du Brenno pendant le Tardiglaciaire.

Ticino glacier (reference values)

Glacier du Ticino (valeurs de référence)

Bedretto Valley

Val Bedretto

Blenio Valley

Val Blenio

Glacial stadial

Stade glaciaire

ELA 2:1

LEG 2:1

(m asl)

ELA depression

Dép. de la LEG

(m/1850 AD)

ELA depression

Dép. de la LEG

(m/1850 AD)

ELA depression

Dép. de la LEG

(m/1850 AD)

Val Corno

C

2,470

65

70-95

-

Alpe di Cruina

M

2,420

115

125-180

110

Maniò

M1

2,375

235

200-250

210-290

Cassina Baggio

A2

2,325

275

280-295

310-420

All’Acqua

A1

2,300

300

315

Fontana

 

2,165

435

 

470-560

Airolo

 

2,075

660

 

600-700

Faido

 

1,915

820

 

800-950

Biasca

 

1,535

1,200

 

1,080-1,200

The reference values (with the reference positions C, M, etc. defined by F. Renner, 1982) are based on the glacial positions occurring on the valley bottom. The ELA depression values for the lateral cirques of the Bedretto Valley (C. Scapozza, unpublished data) and for the whole Blenio Valley (data from Scapozza and Fontana, 2009) are also presented. ELA = Equilibrium Line Altitude.
Les valeurs de référence (avec les positions de référence C, M, etc. définies par F. Renner, 1982) sont basées sur les positions glaciaires caractérisant le fond de vallée. Les valeurs de dépression de la LEG pour les cirques latéraux du Val Bedretto (C. Scapozza, données non publiées) et pour l’ensemble du Val Blenio (données d’après Scapozza et Fontana, 2009) sont également présentées. LEG = Ligne d’Equilibre des Glaciers.

17For the Ticino glacier, the Biasca stadial is defined by a lateral moraine located at Ponte di Iragna, west of Biasca (Hantke, 1983). For the Brenno glacier, a lateral moraine of this stadial located in Chiegnezz, north of Biasca (fig. 5A), together with other morphological and geometrical elements (Scapozza and Fontana, 2009), make it possible to propose a reconstruction of the Brenno (Blenio Valley) and Lesgiüna (Pontirone Valley) glaciers during the Biasca stadial (fig. 5B).

Fig. 5 – The Biasca stadial in the Blenio Valley.
Fig. 5 – Le stade de Biasca dans le Val Blenio.

Fig. 5 – The Biasca stadial in the Blenio Valley. Fig. 5 – Le stade de Biasca dans le Val Blenio.

A: Simplified geomorphological map of the lower Blenio Valley north of Biasca.1: river; 2: debris flow channel; 3: alluvial fan; 4: bank erosion; 5: alluvial deposits; 6: erosional escarpment; 7: landslide; 8: morainic ridge. B: Extent and geometry of the Brenno (Blenio Valley and tributary valleys) and Lesgiüna (Pontirone Valley) glaciers during the Biasca stadial. Coordinates: Swiss Grid system CH1903 / LV03.
A : Carte géomorphologique simplifiée de la partie basse du Val Blenio au nord de Biasca.1 : cours d’eau ; 2 : chenal de lave torrentielle ; 3 : cône de déjection ; 4 : berge d’érosion fluviatile ; 5 : dépôts d’origine fluviatile ; 6 : niche d’arrachement ; 7 : glissement de terrain ; 8 : cordon morainique. B : Extension et géométrie du glacier du Brenno (Val Blenio et vallées latérales) et de la Lesgiüna (Val Pontirone) pendant le stade de Biasca. Coordonnées : système suisse CH1903 / LV03.

Modified from C. Scapozza and G. Fontana, 2009.
Modifiés d’après C. Scapozza et G. Fontana, 2009.

18Considering an ELA depression of between 1,080 and 1,200 m and the fact that this stadial was probably the first progression stadial of the local glaciers during the Lateglacial, C. Scapozza and G. Fontana (2009) proposed a correlation of the Biasca stadial with the Weissbad stadial defined by O. Keller (1988a) in the Säntis massif, on the Eastern side of the Alps (tab. 3).

Tab. 3 – Correlation of the reference Lateglacial stadials, defined for the Ticino and Brenno glaciers in the Leventina/Bedretto and Blenio Valleys, with the Eastern Alps model developed by M. Maisch (1982).
Tab. 3 – Corrélation des stades tardiglaciaires de référence définis pour les glaciers du Ticino et du Brenno dans les vallés de Leventina/Bedretto et de Blenio avec le modèle des Alpes orientales développé par M. Maisch (1982).

Ticino and Brenno glaciers

Glaciers du Ticino et du Brenno

Eastern Alps analogues

Analogues des Alpes orientales

Glacial stadial

Stade glaciaire

ELA depression

Dépression de la LEG

(m/1850 AD)

Glacial stadial

Stade glaciaire

ELA depression

Dépression de la LEG

(m/1850 AD)

Val Corno

65-95

Egesen III (Kartell)

60-120

Alpe di Cruina

110-180

Egesen II (Bocktentälli)

100-150

Maniò

200-290

Egesen I

170-240

Cassina Baggio

275-295

Daun

250-350

All’Acqua

300-420

Fontana

435-560

Clavadel/Senders

380-470

Airolo

600-700

Gschnitz

600-700

Faido

800-950

Steinach

700-800

Biasca

1,080-1,200

(Bühl II) – Weissbad

900-1,000

For the Ticino and Brenno glaciers, the ELA depression is based on the integration of the values presented in tab. 2. ELA = Equilibrium Line Altitude.
Pour les glaciers du Ticino et du Brenno, la dépression de la LEG est basée sur l’intégration des valeurs présentées dans le tab. 2. LEG = Ligne d’Equilibre des Glaciers.

19The Weissbad stadial, with a mean ELA depression of 950 m, probably results from a short and brutal cooling following an important interstadial, characterised by a relatively long phase of regression interrupted by several stagnation phases. The final one was the Appenzell-Konstanz phase (= Bühl 1) of the Rhine glacier (Keller, 1988a; Schoeneich, 1998), leading to the conclusion that the Weissbad stadial can be correlated with the traditional Bühl II stadial of the Eastern Alps (sensu Keller, 1988a), which today is no longer considered as a stadial, but only a “phase of early Lateglacial ice decay” (Reitner, 2007).

20The Biasca stadial was followed by the Faido and Airolo stadials, with the front of the Ticino glacier in the Leventina Valley located in the in the Piottino gorges (Hantke, 1983) and in the region of Airolo. In this last case, the left lateral moraine is located at Valle, east of Airolo (Renner, 1982). Based on this moraine, a past extension of the glaciers on the southern side of the Gotthard Pass was observed by L. Lavizzari (1859-1863) and G. Omboni (1861) in the second half of the 19th century. Based on the moraine morphology, on glaciological arguments and on an ELA depression of 660 m, F. Renner (1982) proposes a correlation between the Airolo stadial and the Gschnitz stadial of the Eastern Alps (tab. 3).

21The following stadials, identified in the Bedretto Valley, are called Fontana and All’Acqua stadials (fig. 6).

Fig. 6 – Reference glacial stadials moraine ridges in the Bedretto Valley.
Fig. 6 – Cordons morainiques de référence des stades glaciaires du Val Bedretto.

Fig. 6 – Reference glacial stadials moraine ridges in the Bedretto Valley. Fig. 6 – Cordons morainiques de référence des stades glaciaires du Val Bedretto.

Mapping and glacial stadial attribution of the moraine ridges from F. Renner (1982) and our own work. Glacial stadials: LIA: Little Ice Age; C: Val Corno; M: Alpe di Cruina; M1: Maniò; A2: Cassina Baggio; A1: All’Acqua. 1: hydrography. Coordinates: Swiss Grid system CH1903 / LV03.
Cartographie et attribution des stades glaciaires des cordons morainiques d’après F. Renner (1982) et notre travail. Stades glaciaires : LIA : Petit Age Glaciaire ; C : Val Corno ; M : Alpe di Cruina ; M1 : Maniò ; A2 : Cassina Baggio ; A1 : All’Acqua. 1 : hydrographie. Coordonnées : système suisse CH1903 / LV03.

22The Fontana stadial is defined by a left lateral moraine located above Soria (west of Fontana), and with an ELA depression of 435. F. Renner (1982) correlated it with the Clavadel/Senders stadial of the Eastern Alps. The All’Acqua stadial presents almost two well-defined positions (tab. 2). The first (position A1) corresponds to the maximum phase and is defined by a left lateral moraine at Cioss Prato (north-west of All’Acqua), while the second one (position A2) is defined by a left latero-frontal moraine just below Cassina Baggio (west of All’Acqua). The ELA depression of 300 m for A1 and of 275 m for A2 (fig. 6) allowed the All’Acqua stadial to be correlated with the Daun stadial of the Eastern Alps (Renner, 1982).

23The last stadials defined for the Ticino glacier in the Bedretto Valley are the Maniò, Alpe di Cruina and Val Corno stadials (tab. 2 and fig. 6). The Maniò stadial is defined by a maximum phase left lateral moraine (position M1) located above Maniò, and by a left latero-frontal moraine from a following phase (position M) located just inside of the maximum phase (Renner, 1982). The Alpe di Cruina stadial is characterised by a well-defined position inside the moraines of the maximum phase of the Maniò stadial (Renner, 1982). Finally, the Val Corno stadial presents a maximum position (position C) marked by several lateral and frontal moraines located between 2,200 and 2,400 m asl on the right side and on the bottom of the Corno Valley (Renner, 1982), in the uppers part of the Bedretto Valley. The ELA depression of the reference positions in the Bedretto Valley are 235 m for the Maniò stadial, 115 m for the Alpe di Cruina stadial and 65 m for the Val Corno stadial (fig. 5). It was then possible for F. Renner (1982) to correlate these three stadials, respectively, with the Egesen I, Egesen II (Bocktentälli) and Egesen III (Kartell) stadials of the Eastern Alps (fig. 2B and tab. 3).

Chronological constraints

The LGM advance

24The maximum age of the LGM advance is constrained by radiocarbon dating of sediments buried by lodgement till attributed to the Episodio Cantù and palaeosoils of the Allogruppo di Besnate, preceding the Alloformazione di Cantù in the regional stratigraphy (fig. 2A). Considering the radiocarbon dates listed in table 1 (with the samples identified by the ID rd-n):

  • rd-7 can be used to date palustrine deposits, partially covered by till, located immediately outside the maximum LGM advance moraines;

  • rd-2, rd-10 and rd-12 were obtained on a palaeosoil buried by lodgement tills of the Alloformazione di Cantù; rd-12 is much younger than the other two dates (referring to the same sample) and may testify a contamination of the sample by more recent elements;

  • rd-8 dates a fossil wood contained in glacial deposits buried by a deltaic sequence of the Breggia river preceding the LGM advance;

  • rd-3 was obtained on fossil wood included in glaciolacustrine deposits buried by ablation till of the LGM advance;

  • rd-6 and rd-9 were measured on fossil woods contained in palustrine deposits buried by lodgement till of the LGM advance, originating from 17.05 and 15.65-15.69 m depth respectively, in a borehole drilled in the Lischee area of Morbio Inferiore;

  • rd-4 and rd-11 can be used to date the Castelnovate Unit, whereas rd-5 can be used to date the Alloformazione di Albusciago, both contained in the Allogruppo di Besnate preceding the LGM advance;

  • Finally, rd-1 was obtained at the top of the Valle della Calcina Media Unit, corresponding to the oldest buried unit of the Allogruppo di Besnate.

  • For the minimum age of the LGM advance, radiocarbon dating of organic material above till of the Episodio Cantù makes it possible to reconstruct the deglaciation chronology in the Como area, in Mendrisiotto and in the lower Lake Verbano:

  • rd-13 was obtained on branches, leafs and seeds found within glaciolacustrine deposits located inside the LGM advance moraines;

  • rd-14 and rd-15 obtained from two boreholes drilled in the city of Como, making it possible to reconstruct the deglaciation of the lower Lario Lake;

  • rd-16 makes it possible to obtain a minimum deglaciation age for the lower Lake Verbano.

The deglaciation

25Concerning the first steps of deglaciation, the radiocarbon date rd-17 makes it possible to establish a minimum age for the Melide stadial, older than 16,000 cal BP. This date was obtained on wood remains and seeds discovered at a depth of 8.05 m in a borehole drilled in the Lake Ceresio close to Bissone (Niessen and Kelts, 1989). The palaeomagnetic declination profile measured in this borehole made it possible to identify the P-lever at a depth of 9.50 m. Thus level was dated in a palaeomagnetic profile measured in Lake Zurich at 18,390–17,130 cal BP (14,600 ± 250 14C BP; laboratory code GL-2; Giovanoli, 1979; Lister, 1985, 1988). This correlation between the two palaeomagnetic profiles makes it possible to define a slightly older minimum age for the Melide stadial (1-2 millennia), and to place it at around 18,000 cal BP.

26For the Biasca, Faido and Airolo stadials, the radiocarbon dating rd-18, rd-19, rd-20 and rd-21 make it possible to place them before 14,000 cal BP. The Fontana and All’Acqua stadials are older than 12,575–11,620 cal BP (rd-24). This is the age of a gyttja on the bottom of a peat bog at Plidutscha (Oberen Tavetsch, GR), making it possible to establish the minimum age of the Selva stadial, corresponding to the All’Acqua stadial in the Bedretto Valley (Renner, 1982). The minimum age of the Maniò stadial is 11,960–11,220 cal BP (rd-25), obtained on the bottom of a peat bog in Val Torta. For the Alpe di Cruina and Val Corno stadials, a minimum age of 7,460–7,025 cal BP (rd-26) was obtained on the bottom of the Alpe di Cruina peat bog.

Discussion

The LGM advance and the beginning of deglaciation

27Considering the maximum and minimum ages presented above, it is possible to propose that the LGM advance in the Southern Swiss Alps is aged between 28,500 and 22,900 cal BP (24,500–19,000 14C BP). This result is approximately the same age as that of the LGM of Alpine glaciers in the northern Alpine Foreland, which generally lie between 26,800 and 21,250 cal BP (22,000–18,000 14C BP) on the Rhone (Swiss lobe), Linth and Rhine glaciers (e.g., Schoeneich, 1998; Preusser, 2004; Ivy-Ochs et al., 2008). Radiocarbon data support the hypothesis that southern Alpine piedmont glaciers reached their maximum extents during Marine Isotope Stage 2 (MIS 2; 29,000–14,500 cal BP) (cf. Schaefer et al., 2006), as suggested for the northern Alpine foreland by S. Ivy-Ochs et al. (2008). In particular, considering the lack of radiocarbon dates between 28,435 cal BP (minimum age of dating rd-10) and 22,900 cal BP (maximum age of dating rd-12), it is therefore possible to correlate tentatively the LGM advance with the GS-3, between 27,400 and 22,700 cal BP on the NGRIP curve (fig. 2B), therefore placing it between the GI-3 and GI-2 interstadials.

28For the Faloppia sub-lobe of the Lario lobe of the Adda glacier, studied in this work (fig. 3A), the Cucciago and the Ca’Morta phases can be identified by a series of moraines following a substantial glacial recession at the end of the LGM (fig. 3B). The hypothetical correlation of the first steps of deglaciation for this sub-lobe with the Greenland isotope stratigraphy (fig. 3C) indicates that the Cucciago and Ca’Morta phases occurred between ca. 22,500 and 21,000 cal BP.

29The Rancate-Castate-Cucciago and Capolago-Roncaccio-Ca’Morta phases were defined on the Ceresio lobe of the confluent Ticino and Adda glaciers and on the Lario lobe of the Adda glacier. On the Verbano lobe of the Ticino glacier, it is very difficult to find unambiguous analogues for these two phases. The attribution of the moraines of Oleggio and of the Lake Varese at the LGM advance (Hantke, 1983) and the definition of the recessional stages by a correlation of the main phases determined on the Rhine and Linth glacier (and defined as “Primo arresto”, Sesto Calende stadial and Ispra stadial, corresponding respectively with the Killwangen/Schaffhausen, Schlieren/Feuenthalen and Zürich/Stein am Rhein stadials defined on the Linth/Rhine glaciers by Keller and Krayss (1993) might be debatable.

30In view of the lack of chronostratigraphical elements, it is very difficult to determine if the Cugnasco stadial of the Verbano lobe of the Ticino glacier can be correlated with the Melide stadial of the Ceresio lobe of the Adda/Ticino glaciers or if it is younger. Considering the dates presented above, the following chronological considerations are proposed for the Pleniglacial and the transition into the Lateglacial (fig. 2):

  • The first recessional phases following the LGM advance (Cucciago and Ca’Morta phases) can be tentatively placed between ca. 22,500 and 21,000 cal BP, and probably corresponds with the two first cold peaks of first order of the GS-2 (fig. 3C);

  • The Melide stadial may corresponds to the first well-defined Lateglacial stadial, placed hypothetically in correspondence with one of the two cold peaks between 20,450 and 19,850 cal BP (fig. 2B);

  • There is nothing to support a correlation between the Cugnasco stadial and the Melide stadial; nevertheless, both phases could probably be placed in the middle of the GS-2c.

The Lateglacial

31The first well-defined stadial in the alpine valleys is the Biasca stadial, when the Ticino (Leventina Valley) and Brenno (Blenio Valley) glaciers were already not in confluence. Considering the correlation with the traditional Bühl II stadial of the Eastern Alps (sensu Keller, 1988a) and the chronological constraints, this stadial could be placed tentatively in correspondence with one of the last cold peaks of the GS-2c (ca. 20,000–18,500 cal BP) at the beginning of Termination I, as also suggested by J. Reitner (2007) for the type-localities of the traditional “Bühl stadial” of the Inn glacier (Northern Tyrol).

32The Biasca stadial, together with preceding Cugnasco stadial and the subsequent Faido stadial, testify the early Lateglacial ice decay, when the Ticino glacier (and the Brenno glacier) readvanced locally several times, as was the case in the Eastern Alps only for small glaciers (Reitner, 2007; Ivy-Ochs et al., 2008). This behaviour shows a response of the Ticino glacier to climatic fluctuations at the beginning of Termination I, which at this time was not the case for the larger dendritic glaciers of the Eastern Alps, which in the main longitudinal valleys were principally stagnant and downwasting ice bodies (Reitner, 2007; Ivy-Ochs et al., 2008).

33Considering its correlation with the Gschnitz stadial of the Eastern Alps, the minimum age of the Airolo stadial can be assumed to be 15,400 ± 1,400 years ago, corresponding to the exposure-age obtained by cosmogenic nuclides dating (Ivy-Ochs et al., 2006) of the type-locality moraines of the Gschnitz stadial at Trins, in the Gschnitz Valley (Tyrol). Radiocarbon dating performed within the moraines of the traditional Steinach stadial type-locality, which precedes the Gschnitz stadial in the Eastern Alps model of the deglaciation (Maisch, 1982), gives an age of 19,840–17,640 cal BP (15,400 ± 470 14C BP; laboratory code VRI-484; van Husen, 1999; Ivy-Ochs et al., 2006). Radiocarbon dating rd-18 and rd-19 make it possible to establish the minimum deglaciation age of the San Bernardino and Lukmanier Passes. It is therefore possible to conclude that the Biasca, Faido and Airolo stadials are older than ca. 16,500 cal BP, with the Biasca and Faido stadials perhaps older than 19,000–18,000 cal BP (i.e. minimum age of the Steinach stadial in the Eastern Alps), and the Airolo stadial probably between 18,000 and 17,000 cal BP, possibly in correspondence with the first cold peaks of GS-2b (fig. 2B). This result is consistent with the compilation of dates and the comparison with the development of vegetation in the Alps, suggesting that the Gschnitz stadial occurred at around 17,500–17,000 cal BP, following a clearly recognizable warming phase (Ivy-Ochs et al., 2008; and references therein).

34The Fontana and All’Acqua stadials are older than the Bølling/Allerød interstadial. Since the minimum age of the Clavadel/Senders stadial of the Eastern Alps is 18,080–15,405 cal BP (13,850 ± 490 14C BP; laboratory code UZ-301; Maisch, 1981), it is possible to hypothetically place the Fontana stadial in correspondence with one of the first cold peaks (> 15,500 cal BP) of the GS-2a. So the All’Acqua stadial probably corresponds with the last cold oscillation of GS-2 (fig. 2B).

35The analogue of the Eastern Alps of the Maniò stadial, the Egesen I stadial, was dated at ca. 12,300 ± 1,500 years ago (Kerschner and Ivy-Ochs, 2008), corresponding to the exposure-age obtained by cosmogenic nuclides dating of the type-locality moraine stabilisation of this stadial, located in the Schönverwall Valley, in Tyrol. Considering this correlation and the minimum age of 11,960–11,220 cal BP (rd-25), the maximum phase of the Maniò stadial could then be placed in correspondence with the coldest peak of GS-1 (ca. 12,500 cal BP), with the following positions placed in correspondence with the subsequent colds peaks. This stadial is then attributed to the beginning of the Younger Dryas.

36For the analogue of the Val Corno stadial in the Eastern Alps, S. Ivy-Ochs et al. (2009) has determined an exposure-age obtained by cosmogenic nuclides dating of the type-locality moraine stabilisation of the Egesen III stadial (Kartell cirque in the Ferwall Groups, Tyrol), of ca. 10,800 ± 1,100 years ago. The Val Corno stadial could then be placed in correspondence with the Greenland Holocene event GH-11.2, chronostratigraphically positioned in the Preboreal stage (fig. 2B).

Synchronicity of deglaciation in the Lepontine and Rhaetian Alps

37As a result of the correlation with the NGRIP Greenland isotopic record, it is also possible to propose a relationship between the stadials defined in the Southern Swiss Alps and the “traditional” glacial stadials model defined in the Eastern Alps. The deglaciation appears to have happen very similarly in the Lepontine and Rhaetian Alps, as was shown in the Monte Leone–Gotthard Alps (Renner, 1982), in Eastern Lepontine Alps (Scapozza and Fontana, 2009) and in the Greina region (Scapozza et al., 2011). This similar behaviour is not surprising since there is a common accumulation zone of the valley glaciers coming from the Gotthard area constituted by the ice domes located in the uppermost Rhone Valley (Rhone ice dome) and in the Surselva (Vorderrhein ice dome; Florineth and Schlüchter, 1998; Bini et al., 2009). Indeed, this geometry of the accumulation zones during the LGM, together with the geomorphological evidences of transgressive glaciers (north to south) over the main alpine passes in the Gotthard area (Nufenen, Gotthard, Lukmanier and Greina Passes; e.g., Florineth and Schlüchter, 1998; Scapozza et al., 2011), indicate that the Ticino glacier was partially supplied with ice coming from the northern side of the Alps.

38Concerning the deglaciation, the synchronicity of their first phases is probably related to the collapse of these ice domes, as indicated by the cosmogenic nuclides dating performed on the Grimsel and Gotthard Passes (Kelly et al., 2006; Hippe et al., 2014). This synchronicity persisted also after the deglaciation of the main Passes, when the accumulation zones became individualised between the northern and southern part of the Alps. This may indicate a similar climatic framework for the Lepontine and Rhaetian Alps during the whole deglaciation, as also suggested by the history of vegetation development until the Preboreal (Burga, 1988).

Conclusion

39Detailed mapping of Quaternary landforms and deposits, and the compilation and calibration of 26 radiocarbon dates ranging from the Po Plain to the Bedretto Valley, made it possible to refine the chronology of the Last Glacial Cycle in the Southern Swiss Alps, and to propose a correlation with the deglaciation model constructed for the Eastern Alps. In particular, the main conclusions proposed here are:

  1. The LGM advance for the Ticino and Adda glaciers was between 28,500 and 22,900 cal BP (24,500-19,000 14C BP). It can be correlated with the GS-3 of the NGRIP Greenland isotopic record. This result is very consistent with the known ages available for the LGM advance in the Northern Swiss Alps, in particular on the Rhone (Swiss lobe), Linth and Rhine glaciers (Schoeneich, 1998; Preusser, 2004; Ivy-Ochs et al., 2008),

  2. For the Pleniglacial and the transition into the Lateglacial, the early recessional phases after the LGM we placed at between ca. 22,500 and 21,000 cal BP. The main phases characterizing this period have not been well defined and further field analyses are required. There are still a number of correlation problems between the Ceresio lobe of the Ticino/Adda glaciers and the Verbano lobe of the Ticino glacier;

  3. In the Leventina/Bedretto and Blenio Valleys, eight glacial stadials are found for the period between ca. 20,000 and 11,200 cal BP. Five of these stadials (Biasca, Faido, Airolo, Fontana and All’Acqua) are in the Oldest Dryas, two (Maniò and Alpe di Cruina) in the Younger Dryas and one (Val Corno) in correspondence with the Greenland Holocene event GH-11.2 (Preboreal). The three last glacial stadials can be easily correlated with the Egesen I, II and III stadials defined in the Eastern Alps.

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Bibliographie

Ambrosi C., Scapozza C., Dall’Agnolo S. (2014) – Stratigrafia dei depositi quaternari del Mendrisiotto. Quaternary Stratigraphy of the Swiss Foreland, CH-QUAT Annual meeting 2014, 22 March 2014, Bern (http://www.ch-quat.ch/en/events/ch-quat-meeting-2014/).

Alessio M., Bella F., Improta S., Belluomini G., Calderoni G., Cortesi C., Manelli G.L., Vigilante A. (1975) – University of Rome carbon-14 dates XIII. Radiocarbon 17, 323-327.

Alessio M., Allegri L. Bella F., Belluomini G., Calderoni G., Cortesi C., Improta S., Manfra L., Orombelli G. (1978) – I depositi lacustri di Rovagnate, di Pontida e di Pianico in Lombardia: datazione con il 14C. Geografia Fisica e Dinamica Quaternaria, 1, 131-137.

Antognini M., Volpers R. (2002) – A Late Pleistocene Age for the Chironico rockslide (Central Alps, Ticino, Switzerland). Bulletin of Applied Geology 7, 113-125.

Bächlin R., Bianconi F., Codoni A., Dal Vesco E., Knoblauch P., Kündig E., Reinhard M., Spänhauer F., Spicher A., Trommsdorff V., Wenk E. (1974)Geologischer Atlas der Schweiz, Blatt 66/Bellinzona, 1:25'000. Schweizerischen Geologischen Kommission, Bern.

Bini A. (1987)L’apparato glaciale würmiano di Como. Tesi di dottorato di ricerca, Università degli studi di Milano, 603 p.

Bini A. (1997) – Stratigraphy, chronology and paleogeography of Quaternary deposits of the area between the Ticino and Olona rivers (Italy – Switzerland). Geologia Insubrica, 2, 21-46.

Bini A., Felber M., Pomicino N., Zuccoli L. (2001)Geologia del Mendrisiotto (Canton Ticino, Svizzera): Messiniano, Pliocene e Quaternario. Ufficio federale delle acque e della geologia, Berna. Rapporti dell’UFAEG – Serie Geologia 1, 462 p.

Bini A., Buoncristiani J.-F., Coutterand S., Ellwanger D., Felber M., Florineth D., Graf H.-R., Keller O., Schlüchter C., Schoeneich P. (2009)La Svizzera durante l’ultimo massimo glaciale (LGM), 1:500’000. Ufficio federale di topografia swisstopo, Wabern.

Blaauw M., Wohlfarth B., Christen J.A., Ampel L., Veres D., Hughen K.A., Preusser F., Svensson (2010) – Were last glacial climate events simultaneous between Greenland and France? A quantitative comparison using non-tuned chronologies. Journal of Quaternary Science 25, 387-394.

Blockley S.P., Lane C.S., Hardiman M., Rasmussen S.O., Seierstad I.K., Steffensen J.P., Svensson A., Lotter A.F., Turney C.S., Bronk Ramsey C., INTIMATE members (2012) – Synchronisation of palaeoenvironmental records over the last 60,000 years, and an extended INTIMATE event stratigraphy to 48,000 b2k. Quaternary Science Reviews 36, 2-10.

Bronk Ramsey C. (2001) – Development of the Radiocarbon Program OxCal. Radiocarbon 43, 355-363.

Bronk Ramsey C. (2014)OxCal 4.2 Manual. University of Oxford, Radiocarbon Accelerator (http://c14.arch.ox.ac.uk/oxcalhelp/hlp_contents.html).

Burga C.A. (1988) – Swiss vegetation history during the last 18’000 years. New Phytologist, 110, 591-602.

Castelletti L., Orombelli G. (1986) – Una nuova data 14C per la storia della deglaciazione del bacino del Lago di Como. Geografia Fisica e Dinamica Quaternaria, 9, 56-58.

Comerci V., Capelletti S., Michetti A.M., Rossi S., Serva L., Vittori E. (2007) – Land subsidence and Late Glacial environmental evolution of the Como urban area (Northern Italy). Quaternary International 173-174, 67-86.

Coutterand S., Nicoud G. (2005) – Les stades de retrait du glacier de l’Arve entre le verrou de Cluses et l’ombilic de Chamonix au cours du Tardiglaciaire (Vallée de l’Arve, Haute-Savoie). Quaternaire, 16, 85-94.

Da Rold O. (1990)L’apparato glaciale del Lago Maggiore, settore orientale. Tesi di Dottorato di Ricerca, Università di Milano, 200 p.

Dorthe-Monachon C., Schoeneich P. (1993) – Ligne d’équilibre des glaciers : le stade de référence 1850 dans les Alpes calcaires occidentales. Geographica Helvetica, 48, 125-134.

Felber M. (1993)La storia geologica del Tardo-Terziario e del Quaternario nel Mendrisiotto (Ticino meridionale, Svizzera). Tesi di dottorato No. 10'125, ETH Zurigo, 617 p.

Felber M. (2000) – Un contributo della geologia del Quaternario alle conoscenze dell’evoluzione del paesaggio nel Ticino durante il I millennio BC. In: de Marinis R.C., Biaggio Simona S. (a cura di): I Leponti, tra mito e realtà. Armando Dadò, Locarno, 57-62.

Florineth D., Schlüchter C. (1998) – Reconstructing the Last Glacial Maximum (LGM) ice surface geometry and flowlines in the Central Swiss Alps. Eclogae geologicae Helvetiae, 91, 391-407.

Giovanoli F. (1979) – A comparison of the magnetization of detrital and chemical sediment from Lake Zürich. Geophysical Research Letters 6, 233-235.

Gross G., Kerschner H., Patzelt G. (1977) – Methodische Untersuchungen über die Schneegrenze in alpinen Gletschergebieten. Zeitschrift für Gletscherkunde und Glazialgeologie, 12, 223-251.

Hantke R. (1983)Eiszeitalter. Die jüngste Erdgeschichte der Schweiz und ihrer Nachbargebiete. 3: Westliche Ostalpen mit ihrem bayerischen Vorland bis zum Inn-Durchbruch und Südalpen zwischen Dolomiten und Mont-Blanc. Ott Verlag, Thun, 730 p.

Hippe K., Ivy-Ochs S, Kober F., Zasadni J., Wieler R., Wacker L., Kubik P.W., Schlüchter C. (2014) – Chronology of Lateglacial ice flow reorganization and deglaciation in the Gotthard Pass area, Central Swiss Alps, based on cosmogenic 10B and in situ 14C. Quaternary Geochronology 19, 14-26.

Ivy-Ochs S., Kerschner H., Kubik P.W., Schlüchter C. (2006) – Glacier response in the European Alps to Heinrich Event 1 cooling: the Gschnitz stadial. Journal of Quaternary Science 21, 115-130.

Ivy-Ochs S., Kerschner H., Schlüchter C. (2007) – Cosmogenic nuclides and the dating of Lateglacial and Early Holocene glacier variations: the Alpine perspective. Quaternary International 164/165, 53-63.

Ivy-Ochs S., Kerschner H., Reuther A., Preusser F., Heine K., Maisch M., Kubik P.W., Schlüchter C. (2008) – Chronology of the last glacial cycle in the European Alps. Journal of Quaternary Science 23, 559-573.

Ivy-Ochs S., Kerschner H., Maisch M., Christl M., Kubik P.W., Schlüchter C. (2009) – Latest Pleistocene and Holocene glaciers variations in the European Alps. Quaternary Science Reviews 28, 2137-2149.

Johnsen S., Dahl-Jensen D., Gundestrup N., Steffensen J.P., Clausen H.B., Miller H., Masson-Delmotte V., Sveinbjörnsdottir A.E., White J. (2001) – Oxygen isotope and palaeotemperature records from six Greenland ice-core stations: Camp Century, Dye-2, GRIP, GISP2, Renland and NorthGRIP. Journal of Quaternary Science 16, 299-307.

Keller O. (1988a) – Altere spätwürmzeitliche Gletschervorstosse und Zerfall des Eisstromnetzes in den nördlichen Rhein-Alpen (Weissbad-Stadium/Bühl-Stadium). Physische Geographie, 27, 1-241.

Keller W.A. (1988b) – Liste der 14C-daten 1975–1987. Physische Geographie, 26, 1-52.

Keller O., Krayss E. (1993) – The Rhine-Linth glacier in the upper Würm: a model of the last alpine glaciation. Quaternary International 18, 15-27.

Kelly M.A., Ivy-Ochs S., Kubik P.W., Von Blanckenburg F., Schlüchter C. (2006) – Chronology of deglaciation based on 10Be dates of glacial erosional features in the Grimsel Pass region, central Swiss Alps. Boreas 35, 634–643.

Kerschner H. (1976) – Untersuchungen zum Daun- und Egesenstadium in Nordtirol und Graubünden (methodische Überlegungen). Geographischer Jahresbericht aus Osterreich, 36, 26-49.

Kerschner H., Ivy-Ochs S. (2008) – Palaeoclimate from glaciers: examples from the Eastern Alps during the Alpine Lateglacial and early Holocene. Global and Planetary Change 60, 58-71.

Küttel M. (1977) – Pollenanalytische und geochronologische Untersuchungen zur Piottino-Schwankung (Jüngere Dryas). Boreas 6, 259-274.

Lavizzari L. (1859–1863) Escursioni nel Cantone Ticino. Tipografia Francesco Veladini e Co., Lugano, 978 p.

Lister G.S. (1985)Late Pleistocene alpine deglaciation and Post-glacial climatic developments in Switzerland: the record from sediments in a peri-alpine lake basin. PhD Thesis Nr. 7753, ETH Zürich, 151 p.

Lister G.S. (1988) – A 15,000-year isotopic record from Lake Zürich of deglaciation and climatic change in Switzerland. Quaternary Research 29, 129-141.

Maisch M. (1981)Glazialmorphologische und Gletschergeschichtliche Untersuchungen im gebiet zwischen Landwasser- und Albulatal (Kt. Graubünden, Schweiz). PhD Thesis, Universität Zürich. Physische Geographie, 3, 1-215.

Maisch M. (1982) – Zur Gletscher- und Klimageschichte des alpinen Spätglazials. Geographica Helvetica, 37, 93-104.

Miallier D., Lefèvre J.-C. (2013) – Quelques remarques sur la présentation des données chronologiques concernant la période Quaternaire. Quaternaire, 24, 391-395.

Müller H.J. (1972) – Pollenanalytische Untersuchungen zum Eisrückzug und zur Vegetationsgeschichte im Vorderrhein- und Lukmaniergebiet. Flora, 161, 333-382.

Müller H.-N., Kerschner H., Küttel M. (1980) – Gletscher- und vegetationsgeschichtliche Untersuchungen im Val de Nendaz (Wallis) – Ein Beitrag zur Alpinen Spätglazialchronologie. Zeitschrift für Gletscherkunde und Glazialgeologie, 16, 61-84.

NGRIP–Members (2004a) – High resolution record of Northern Hemisphere climate extending into the last interglacial period. Nature 431, 147-151.

NGRIP–Members (2004b) North Greenland Ice Core Project Oxygen Isotope Data. IGBP PAGES/World Data Center for Paleoclimatology Data Contribution Series n. 2004-059. NOAA/NGDC Paleoclimatology Program, Boulder (CO).

Niessen F., Kelts K. (1989) – The deglaciation and Holocene sedimentary evolution of southern perialpine Lake Lugano – implications for Alpine paleoclimate. Eclogae geologicae Helvetiae, 82, 235-263.

Oeschger H., Riesen T., Lerman J.C. (1970) – Bern radiocarbon dates VII. Radiocarbon 12, 358-384.

Omboni G. (1861) – I ghiacciaj antichi e il terreno erratico in Lombardia. Atti della Società Italiana di Scienze Naturali, 3, 232-299.

Orombelli G. (1974) – Alcune date 14C per il Quaternario lombardo. Studi Trentini di Scienze Naturali, 51, 125-127.

Orombelli G. (1983a) – I depositi würmiani del Comasco. Geografia Fisica e Dinamica Quaternaria, 6, 174-175.

Orombelli G. (1983b) – Il Pleistocene superiore in Italia – I depositi glaciali. Geografia Fisica e Dinamica Quaternaria, 6, 179-180.

Penck A., Brückner E. (1909)Die Alpen im Eiszeitalter. Tauchnitz, Leipzig, 3 vol.

Porter S.C., Orombelli G. (1982) – Late-glacial ice advances in the western Italian Alps. Boreas 11, 125-140.

Preusser F. (2004) – Toward a chronology of the Late Pleistocene in the northern Alpine Foreland. Boreas 33, 195-210.

Renner F. (1982)Beiträge zur Gletscher-Geschichte des Gotthardgebietes und Dendroklimatologische Analysen an Fossilen Hölzern. PhD Thesis, Universität Zürich. Physische Geographie, 8, 180  p.

Reimer P.J., Bard E., Bayliss A., Beck J.W., Blackwell P.G., Bronk Ramsey C., Buck C.E., Cheng H., Edwards R.L., Friedrich M., Grootes P.M., Guilderson T.P., Haflidason H., Hajdas I., Hatté C., Heaton T.J., Hoffmann D.L., Hogg A.G., Hughen K.A., Kaiser K.F., Kromer B., Manning S.W., Niu M., Reimer R.W., Richards D.A., Scott E.M., Southon J.R., Staff R.A., Turney C.S., van der Plicht J. (2013) – IntCal13 and Marine13 radiocarbon age calibration curves, 0–50’000 years cal BP. Radiocarbon 55, 1869-1887.

Reitner J.M. (2007) – Glacial dynamics at the beginning of Termination I in the Eastern Alps and their stratigraphic implications. Quaternary International 164-165, 64-84.

Rossi S., Alberti F., Felber M., Bini A. (1991) – Evidenze di fluttuazioni glaciali würmiane nella bassa valle della Breggia (Cernobbio, Como). Bollettino della Società ticinese di Scienze naturali, 79, 25-47.

Scapozza C., Fontana G. (2009) – Le Alpi Bleniesi. Storia glaciale e periglaciale e patrimonio geomorfologico. Memorie della Società ticinese di Scienze naturali e del Museo cantonale di storia naturale, Lugano, 10, 1-111.

Scapozza C., Antognini M., Oppizzi P., Patocchi N. (2012) – Stratigrafia, morfodinamica, paleoambienti della piana fluvio-deltizia del Ticino dall’Ultimo Massimo Glaciale a oggi: proposta di sintesi. Bollettino della Società ticinese di Scienze naturali, 100, 89-106.

Scapozza G., Scapozza C., Reynard E. (2011) – Morphogénèse de la région de la Greina depuis le Dernier Maximum Glaciaire. In Lambiel C., Reynard E., Scapozza C. (éds.) : La géomorphologie alpine : entre patrimoine et contrainte. Actes du colloque de la Société Suisse de Géomorphologie, 3-5 septembre 2009, Olivone. Université de Lausanne, Institut de géographie, Géovisions, 36, 99-111.

Schaefer J.M., Denton G.H., Barrell D.J., Ivy-Ochs S., Kubik P.W., Andersen B.G., Phillips F.M., Lowell T.V., Schlüchter C. (2006) – Near-synchronous interhemispheric termination of the last glacial maximum in mid-latitudes. Science 312, 1510-1513.

Schlüchter C. (1988) – The deglaciation of the Swiss-Alps. A paleoclimatic event with chronological problems. Bulletin de l’Association Française pour l’étude du Quaternaire 2/3, 141-145.

Schneider R.E. (1978) – Pollenanalytische Untersuchungen zur Kenntnis der spät- und postglazialen Vegetationsgeschichte am Südrand der Alpen zwischen Turin und Varese (Italien). Botanische Jahrbücher für Systematik, Pflanzengeschichte und Pflanzengeographie, 100, 26-109.

Schoeneich P. (1998) – Corrélation du dernier maximum glaciaire et de la déglaciation alpine avec l’enregistrement isotopique du Groenland. Quaternaire, 9, 203-215.

Schoeneich P., Dorthe-Monachon C., Jaillet S., Ballandras S. (1997) – Le retrait glaciaire dans les vallées des Préalpes et des Alpes au Tardiglaciaire. Bulletin d’études préhistoriques et archéologiques alpins, Numéro spécial consacré aux Actes du VIII Colloque International sur les Alpes dans l’Antiquité, Sion, 26–28 septembre 1997, 23-37.

van Husen D. (1999) – Geological processes during the Quaternary. Mitteilungen der Österreichischen Geologischen Gesellschaft, 92, 135-156.

Zoller H., Kleiber H. (1971) – Vegetationsgeschichtliche Untersuchungen in der montanen und subalpinen Stufe der Tessinertäler. Verhandlungen der Naturforschenden Gesellschaft in Basel, 81, 91-153.

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Annexe

Version française abrégée

Après le travail pionnier de A. Penck et E. Brückner (1909), plusieurs recherches se sont focalisées sur l’extension des glaciers de piedmont et sur la déglaciation dans les Alpes. Avec ces études, le schéma développé au début du 20e siècle comprenant seulement trois stades principaux (Bühl, Gschnitz et Daun) est devenu plus complexe. Il comprend aujourd’hui au moins six stades majeurs reconnus dans plusieurs régions des Alpes (Müller et al., 1980; Maisch, 1982; Schoeneich et al., 1997; Coutterand et Nicoud, 2005). Grâce à la détermination des âges d’exposition à l’aide des isotopes cosmogéniques, la chronologie du dernier cycle glaciaire a également été affinée de manière considérable depuis la fin du 20e siècle, en particulier dans les Alpes Orientales (Ivy-Ochs et al., 2007, 2008 ; Reitner, 2007).

Jusqu’à ce jour, il a été admis notamment par des chercheurs du Nord de l’Italie (Bini, 1997 ; Bini et al., 2009) que le Sud des Alpes Suisses présentait une histoire des glaciations quaternaires différente par rapport au reste des Alpes Suisses. Ceci est dû probablement à l’absence de datations des âges d’exposition à l’aide d’isotopes cosmogéniques et de la sous-exploitation des datations radiocarbone disponibles. Pour ces raisons, le versant sud des Alpes a souvent été négligé dans les synthèses concernant la déglaciation dans les Alpes Suisses (Schlücher, 1988 ; Schoeneich, 1998 ; Ivy-Ochs et al., 2008).

Le levé des formes et dépôts du Quaternaire de la feuille 1373/Mendrisio pour l’Atlas géologique de la Suisse au 1:25000 (Ambrosi et al., 2014), et la compilation de 26 datations radiocarbone pour les glaciers du Ticino et de l’Adda au Pléistocène récent (fig. 1) a rendu possible la reconstitution d’une nouvelle géométrie et chronologie du DMG et de définir les principales étapes de la déglaciation dans le Sud des Alpes Suisses. À l’aide de la chronologie de la déglaciation élaborée en combinaison avec le calcul de la Dépression de la Ligne d’Equilibre des Glaciers (DLEG) pour les principaux stades glaciaires reconnus, un essai de corrélation des stades glaciaires définis dans la vallée du Ticino avec le modèle des Alpes Orientales est proposé ici. La DLEG a été calculée par soustraction de la LEG déterminée en utilisant la méthode de partage des surfaces et considérant un AAR (Accumulation Area Ratio) de 0,67 (Kerschner, 1976 ; Gross et al., 1977) du niveau de référence de la fin du Petit Age Glaciaire (Dorthe-Monachon et Schoeneich, 1993). Sur la base de cette approche, il est également possible de corréler les fluctuations glaciaires mises en évidence avec l’enregistrement isotopique groenlandais du sondage NGRIP (North Greenland Ice Core Project ; voir NGRIP-Members, 2004a) sur la base de la stratigraphie INTIMATE (INTegration of Ice core, Marine and TErrestrial records of the last termination ; voir Blockley et al., 2012).

Toutes les données radiocarbone compilées (tab. 1 et fig. 2A) ont été calibrées grâce au logiciel OxCal 4.2 (Bronk Ramsey, 2014) sur la base de la courbe de calibration IntCal13 (Reimer et al., 2013) et avec un intervalle de confiance de 2σ (95,4 % de probabilité).

D'un point de vue chronologique, les datations des dépôts recouverts, respectivement couvrant ceux relatifs à l’Episodio Cantù, défini comme l’avancée maximale des glaciers du Sud des Alpes pendant le dernier cycle glaciaire (Bini 1987; Felber, 1993; Bini et al., 2001), ont permis de déterminer un âge du DMG pour les glaciers du Ticino et de l’Adda compris entre 28500-22900 cal BP (24500 et 19000 14C BP). Il a donc été possible de proposer une corrélation du DMG avec le stade isotopique GS-3, compris entre 27400 et 22700 cal BP sur la courbe du forage NGRIP (fig. 2B). Ce résultat est cohérent avec l’âge du DMG déterminé au Nord des Alpes Suisses, qui est généralement compris entre 26800-21250 cal BP (22000 et 18000 14C BP) pour les glaciers du Rhône (lobe Suisse), de la Linth et du Rhin (Schoeneich, 1998 ; Preusser, 2004 ; Ivy-Ochs et al., 2008), ce qui permet de le placer entre les interstades GI-3 et GI-2.

Les premières phases de la déglaciation ont été détaillées en particulier pour le sous-lobe de la Faloppia, partie du lobe du Lario du glacier de l’Adda (fig. 3A), permettant de déterminer les équivalents des phases de Cucciago et Ca’Morta définies par M. Felber (1993) et A. Bini et al. (2001). La corrélation hypothétique de ces phases avec la stratigraphie isotopique du Groënland a permis de proposer un âge compris entre 22500 et 21000 cal BP (fig. 3B, C).

Pour les stades suivants, seul celui de Melide du lobe du Ceresio est bien précisé, avec un âge minimal d’environ 18000 cal BP permettant de proposer une corrélation avec l’un des deux pics froids placés entre 20450 et 19850 cal BP sur la courbe NGRIP. Celui-ci pourrait correspondre au stade de Cugnasco défini sur le lobe du Verbano du glacier du Ticino (fig. 4).

Le premier véritable stade tardiglaciaire à l’intérieur des vallées supérieures est celui de Biasca (fig. 5). Sur la base d’arguments paléoclimatiques et d’une DLEG comprise entre 1 080 et 1 200 m, C. Scapozza et G. Fontana (2009) ont proposé une corrélation avec le stade de Weissbad défini par O. Keller (1988a) dans le massif du Säntis, en Suisse Orientale, correspondant à l’ancien stade de Bühl II des Alpes Orientales (tab. 3), qui aujourd’hui n’est plus considéré comme un stade mais plutôt comme une phase de décroissance glaciaire du début du Tardiglaciaire (Reitner, 2007).

Pour la suite du Dryas ancien, quatre autres stades glaciaires (Faido, Airolo, Fontana et All’Acqua) ont été définis. Les datations disponibles permettent de conclure que les stades de Biasca, Faido et Airolo sont plus anciens que 16500 cal BP. Si l’on tient compte également des corrélations avec les Alpes Orientales, les stades de Biasca et de Faido seraient antérieurs à 19000-18000 cal BP (âge minimal du stade de Steinach dans les Alpes Orientales ; voir van Husen, 1999 ; Ivy-Ochs et al., 2006) et le stade d'Airolo serait probablement compris entre 18000 et 17000 cal BP (fig. 2B). Pour les stades de Fontana et All’Acqua, un âge minimal de ce dernier de 12575–11620 cal BP (rd-24) permet de conclure qu’ils sont antérieurs à l’interstade du Bølling/Allerød et qu'ils peuvent donc être attribués au stade isotopique GS-2a.

Les trois derniers stades définis dans le Val Bedretto, ceux de Maniò, Alpe di Cruina et Val Corno (fig. 6), peuvent être respectivement corrélés avec une bonne certitude avec les stades de l’Egesen I (Egesen maximal), Egesen II (Bocktentälli) et Egesen III (Kartell) des Alpes Orientales. Les âges minimaux de ces stades permettent d’attribuer ceux de Maniò et de l’Alpe di Cruina au stade isotopique groenlandais GS-1 (Dryas récent) et celui de Val Corno est associé à l’épisode froid holocène GH-11.2 (Préboréal).

La corrélation des stades glaciaires définis au Sud des Alpes avec ceux des Alpes Orientales a permis de souligner une chronologie de la déglaciation assez similaire entre le Sud et le Nord des Alpes Suisses. Cela n’a rien de surprenant si l’on considère une zone d’accumulation commune entre les glaciers de vallée provenant de la région du Gothard constituée par des dômes de glace situés dans la partie supérieure de la Vallée du Rhône (dôme de glace du Rhône) et dans la Haute Surselva (dôme de glace du Vorderrhein ; Florineth et Schlüchter, 1998 ; Bini et al., 2009). En effet, cette géométrie des zones d’accumulation des glaciers pendant le DMG, ainsi que les évidences géomorphologiques de diffluences glaciaires (du nord vers le sud) aux principaux cols (Cols du Nüfenen, du Gothard, du Lukmanier et de la Greina) de la région du Gothard (Florineth et Schlüchter, 1998 ; Scapozza et Fontana, 2009 ; Scapozza et al., 2011), indiquent une alimentation partielle du glacier du Ticino par des glaces provenant du côté Nord des Alpes.

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Table des illustrations

Titre Fig. 1 – Localisation of the study area, representation of the glacial extent during the LGM and position of the discovered organic material supplying the radiocarbon dating presented in tab. 1 and in fig. 2A. Fig. 1 – Localisation du secteur étudié, représentation de l’extension glaciaire pendant le DMG et position des découvertes de matériel organique ayant permis les datations radiocarbone présentées dans le tab. 1 et dans la fig. 2A.
Légende The radiocarbon dating number corresponds to the numbers in the first column of tab. 1. The positions of dating rd-1, rd-4, rd-7, rd-11 and rd-13 are not represented because they lie outside of the map frame. 1: main pass; 2: radiocarbon dating; 3: Faloppia sub-lobe. Equidistance of the contour lines: 200 m. L'identifiant de la datation radiocarbone correspond à l'identifiant de la première colonne de la tab. 1. La position des datations rd-1, rd-4, rd-7, rd-11 et rd-13 n’est pas représentée parce qu’elle se situe en dehors du cadre de la carte. 1 : col principal ; 2 : datation radiocarbone ; 3 : sous-lobe de la Faloppia. Equidistance des courbes de niveau : 200 m.
Crédits Modified from Bini et al., 2009. Modifié d’après Bini et al., 2009.
URL http://geomorphologie.revues.org/docannexe/image/10753/img-1.png
Fichier image/png, 1,3M
Titre Fig. 2 – Correlation of the main deglaciation stadials in the Southern Swiss Alps with the Greenland isotopic stratigraphy. Fig. 2 – Corrélation des principaux stades de déglaciation du Sud des Alpes Suisses avec la stratigraphie isotopique du Groenland.
Légende A: Box plot of the radiocarbon dates compiled in tab. 1. 1: organic material within the tills of the Episodio Cantù (= minimum age of the LGM and minimum deglaciation age of the Como area, Mendrisiotto and lower Lake Verbano); 2: sediments buried by lodgement till of the Episodio Cantù (= LGM) and palaeosoils of the Allogruppo di Besnate (precedent the Episodio Cantù); GL-2: radiocarbon dating of the P-level on a geomagnetical profile. B: Correlation hypothesis between the LGM and the main Lateglacial stadials of the Ticino/Adda glaciers, and the Eastern Alps analogues and with the isotope stratigraphy of the Greenland ice core NGRIP (numerical data from NGRIP-Members, 2004b).A : Graphique des datations radiocarbone compilées dans le tab. 1. 1 : matériel organique dans les tills de l’Episodio Cantù (= âge minimal du DMG et de la déglaciation de la zone de Como, du Mendrisiotto et du bas Lac Verbano) ; 2 : sédiments enterrés par les tills de fond de l’Episodio Cantù (=DMG) et paléosols de l’Allogruppo di Besnate (précédant l’Episodio Cantù) ; GL-2: Datation radiocarbone du niveau P dans un profil géomagnétique. B : Hypothèses de corrélation du DMG et des principaux stades tardiglaciaires des glaciers du Ticino et de l’Adda avec les analogues des Alpes Orientales et avec la stratigraphie isotopique groenlandaise du forage NGRIP (données numériques d’après NGRIP-Members, 2004b).
URL http://geomorphologie.revues.org/docannexe/image/10753/img-2.png
Fichier image/png, 209k
Titre Fig. 3 – First deglaciation phases following the LGM advance: example of the Faloppia sub-lobe of the Adda glacier in the Chiasso region. Fig. 3 – Premières phases de la déglaciation suivant le DMG : exemple du sous-lobe de la Faloppia du glacier de l’Adda dans la région de Chiasso.
Légende A: Simplified Quaternary geological map. 1: moraine ridge; 2: kame terrace; 3: moraine ridge number. Coordinates: Swiss Grid system CH1903 / LV03. B: Synthetic sketch of the deglaciation of the Faloppia sub-lobe, based on the glacial positions determined by the progression or main stagnation moraines (the numerical code of the moraine ridges refers to the enumeration reported in A). 1: glacial position; 2: kame terrace; 3: important glacial recession. C: Essay of correlation between the Faloppia sub-lobe deglaciation and the isotope stratigraphy of the Greenland ice core NGRIP. A : Carte géologique simplifiée du Quaternaire. 1 : cordon morainique ; 2 : terrasse de kame ; 3 : numéro du cordon morainique. Coordonnées : système suisse CH1903 / LV03. B : Schéma de synthèse de la déglaciation du sous-lobe de la Faloppia basée sur les positions glaciaires déterminées grâce aux principaux cordons morainiques de progression ou de stagnation (le code numérique des cordons morainiques fait référence à l’énumération reportée en A). 1 : position glaciaire ; 2 : terrasse de kame ; 3 : régression glaciaire importante. C : Essai de corrélation de la déglaciation du sous-lobe de la Faloppia avec la stratigraphie isotopique groenlandaise du forage NGRIP.
Crédits Numerical data from NGRIP-Members, 2004b.Données numériques d’après NGRIP-Members, 2004b.
URL http://geomorphologie.revues.org/docannexe/image/10753/img-3.png
Fichier image/png, 850k
Titre Fig. 4 – Palaeogeography of the lower Ticino Valley at the beginning of the Lateglacial during the Cugnasco stadial. Fig. 4 – Paléogéographie de la partie basse de la Vallée du Ticino au début du Tardiglaciaire pendant le stade de Cugnasco.
Légende 1: moraine ridge; 2: Ticino glacier; 3: palaeo Verbano Lake; 4: iceberg. 1 : cordon morainique ; 2 : glacier du Ticino ; 3 : paléo Lac Verbano ; 4 : iceberg.
Crédits Modified from C. Scapozza et al. (2012).Modifié d’après Scapozza et al. (2012).
URL http://geomorphologie.revues.org/docannexe/image/10753/img-4.png
Fichier image/png, 1,2M
Titre Fig. 5 – The Biasca stadial in the Blenio Valley. Fig. 5 – Le stade de Biasca dans le Val Blenio.
Légende A: Simplified geomorphological map of the lower Blenio Valley north of Biasca.1: river; 2: debris flow channel; 3: alluvial fan; 4: bank erosion; 5: alluvial deposits; 6: erosional escarpment; 7: landslide; 8: morainic ridge. B: Extent and geometry of the Brenno (Blenio Valley and tributary valleys) and Lesgiüna (Pontirone Valley) glaciers during the Biasca stadial. Coordinates: Swiss Grid system CH1903 / LV03. A : Carte géomorphologique simplifiée de la partie basse du Val Blenio au nord de Biasca.1 : cours d’eau ; 2 : chenal de lave torrentielle ; 3 : cône de déjection ; 4 : berge d’érosion fluviatile ; 5 : dépôts d’origine fluviatile ; 6 : niche d’arrachement ; 7 : glissement de terrain ; 8 : cordon morainique. B : Extension et géométrie du glacier du Brenno (Val Blenio et vallées latérales) et de la Lesgiüna (Val Pontirone) pendant le stade de Biasca. Coordonnées : système suisse CH1903 / LV03.
Crédits Modified from C. Scapozza and G. Fontana, 2009.Modifiés d’après C. Scapozza et G. Fontana, 2009.
URL http://geomorphologie.revues.org/docannexe/image/10753/img-5.png
Fichier image/png, 1,1M
Titre Fig. 6 – Reference glacial stadials moraine ridges in the Bedretto Valley. Fig. 6 – Cordons morainiques de référence des stades glaciaires du Val Bedretto.
Légende Mapping and glacial stadial attribution of the moraine ridges from F. Renner (1982) and our own work. Glacial stadials: LIA: Little Ice Age; C: Val Corno; M: Alpe di Cruina; M1: Maniò; A2: Cassina Baggio; A1: All’Acqua. 1: hydrography. Coordinates: Swiss Grid system CH1903 / LV03. Cartographie et attribution des stades glaciaires des cordons morainiques d’après F. Renner (1982) et notre travail. Stades glaciaires : LIA : Petit Age Glaciaire ; C : Val Corno ; M : Alpe di Cruina ; M1 : Maniò ; A2 : Cassina Baggio ; A1 : All’Acqua. 1 : hydrographie. Coordonnées : système suisse CH1903 / LV03.
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Cristian Scapozza, Claudio Castelletti, Linda Soma, Stephan Dall’Agnolo et Christian Ambrosi, « Timing of LGM and deglaciation in the Southern Swiss Alps », Géomorphologie : relief, processus, environnement, vol. 20 - n° 4 | 2014, 307-322.

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Cristian Scapozza, Claudio Castelletti, Linda Soma, Stephan Dall’Agnolo et Christian Ambrosi, « Timing of LGM and deglaciation in the Southern Swiss Alps », Géomorphologie : relief, processus, environnement [En ligne], vol. 20 - n° 4 | 2014, mis en ligne le 01 janvier 2016, consulté le 27 mars 2017. URL : http://geomorphologie.revues.org/10753 ; DOI : 10.4000/geomorphologie.10753

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Auteurs

Cristian Scapozza

Institute of Earth Sciences – University of Applied Sciences and Arts of Southern Switzerland (SUPSI) – Campus Trevano – 6952 Canobbio – Switzerland (cristian.scapozza@supsi.ch).

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Claudio Castelletti

Institute of Earth Sciences – University of Applied Sciences and Arts of Southern Switzerland (SUPSI) – Campus Trevano – 6952 Canobbio – Switzerland.

Linda Soma

Institute of Earth Sciences – University of Applied Sciences and Arts of Southern Switzerland (SUPSI) – Campus Trevano – 6952 Canobbio – Switzerland).

Stephan Dall’Agnolo

Swiss Geological Survey – Federal Office of Topography swisstopo – Seftigenstrasse 264 – 3084 Wabern – Switzerland (Stephan.Dall’Agnolo@swisstopo.ch).

Christian Ambrosi

Institute of Earth Sciences – University of Applied Sciences and Arts of Southern Switzerland (SUPSI) – Campus Trevano – 6952 Canobbio – Switzerland.

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