s n s n - saseg · cima lunga (adula) maggia (vogorno ) maggia (cocco gneiss) strona ceneri simano...
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On the "root zone" of the Alpine nappes in the Ticino area (Ivrea Zone, Insubric line and gneisses of the Southern Steep
Belt): Geometry and kinematics
Stefan M. Schmid
84th CONVENTION 2017 Ascona, Switzerland, Monte Verità, June 17–19, 2017
Livo gorge near Lake Como View from Losone towards Arcegno
S N S N
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OROGEN-SCALE
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Austroalpine
Southern Alps
The Insubric line; part of the Periadriatic line
Main activity of the Insubric Line: 32-20 Ma. The eastern segments (Pustertal- Gailtal- and Balaton-lines) are also active after 20 Ma, when the
Periadriatic line became offset by the Giudiarie line the Eastern Alps became laterally extruded to the east.
200 km
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140 km
103 km 45 Ma 35 Ma
25 Ma 0 Ma
reconstruction for the last 45 Ma after Schmid et al. (2017), Europe fixed
estimate of the amount of dextral strike slip, based on the reconstruction of the movement of the Ivrea mantle wedge (green) for the last 35 Ma: 140 km
Estimate of the amount of dextral strike slip
Schmid et al. 2017
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Estimate of backthrusting along the Insubric Line
22 km
Schmid et al. 2004
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Large amounts of exhumation by retro-thrusting and Subsequent erosion restricted to the Lepontine dome
Oberhänsli et al. 2004
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The Lepontine dome in map view
Simano & Leventina- Lucomagno
M. Rosa Bellinzona- Dascio
Zermatt- Saas Fee
Gotthard nappe
Schmid et al. 2017
limit amphibolite
grade
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The Lepontine dome in profile view
Schmid et al. 2017
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Ivrea Zone
Ticino & Lombardian S. Alps
S. Alps preserve a passive margin
Granulite facies mafics Granulite facies metapelites
Passive margin formation exhumed Ivrea zone
Age of peak-T: Permian!!!!
Schmid et al. 1989
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LOCAL GEOLOGY, OUTCROPS, THIN SECTIONS
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Canavese Line (eastern branch of Insubric line) in Valle d’Ossola
NW SE
Ivrea Zone Sesia Zone
Zingg et al. 1990
SE NW
SE NW
SOUTHERN ALPS CENTRAL ALPS
CENTRAL ALPS SOUTHERN ALPS
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Insubric line near Ascona
N S
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Arcegno
Losone
Ivrea Zone Sesia-derived
mylonites
Canavese Mesozoic
Sesia Zone P.-L. Ocean Zerm.-Saas
Zone
Monte Rosa nappe
N S Ivrea-derived mylonites
2 km
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Schmid et al. 1987 & 1989
The northern part of the mylonite belt records steep lineations, indicating back- thrusting. The southern part of the mylonite belt records sub- horizontal lineations, Indicating dextral strike slip
subhorizontal lineations = strike slip
down-dip lineations = back-thrusting
backthrusting and strike slip displacements
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Fault rocks at the Insubric line 1
mafic rocks Ivrea Zone paragneisses Ivrea Zone
pseudotachylite
cataclasite pre-Alpine fabric
Ivrea-derived mylonite
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Fault rocks at the Insubric line 2
mylonitized Mesozoic limestone Sesia-derived mylonites
lineations
sheath fold
sigma clasts
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1
2
3$
4$
5$
6$7$
8$
our hotel
Grotto Zelinda
tectonic map of the Arcecno area and excursion day 2
unpublished
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Monte Rosa
Insubric mylonites
Sesia
Ivrea
Onsermone zone
(Antigorio)
Belinzona-Dascio zone (Valaisan?)
Maggia
Belinzona-Dascio zone
Cima Lunga (Adula)
Maggia (Vogorno)
Maggia (Cocco gneiss)
Strona Ceneri
Simano (490Ma granite gneiss)
Lavertezzo
Zerm.-Saas Fee
southern part of the Lepontine dome
Berger & Merolli 2005
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foliations and lineations
mostly Eduard Wenk unpublished compiled by S. Schmid
lineations foliations
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foliations, lineations & tectonic map
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Simano nappe
Bellinzona-‐Dascio Zone
Insubric line
Profile across the southernmost Lepontine dome
Geology of Switzerland Guide Book 1980
2. stop 1. stop
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Polyphase folding in the Lepontine dome at Lavertezzo
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