Tectonics of the Lepontine Alps: ductile thrusting and folding in the deepest tectonic levels of the Central Alps

Details

Ressource 1Download: serval:BIB_532E1656A079.P001 (3614.39 [Ko])
State: Public
Version: author
License: Not specified
It was possible to publish this article open access thanks to a Swiss National Licence with the publisher.
Serval ID
serval:BIB_532E1656A079
Type
Article: article from journal or magazin.
Collection
Publications
Institution
Title
Tectonics of the Lepontine Alps: ductile thrusting and folding in the deepest tectonic levels of the Central Alps
Journal
Swiss Journal of Geosciences
Author(s)
Steck A., Della Torre F., Keller F., Pfeifer H.-R., Hunziker J., Masson H.
ISSN
1661-8726
ISSN-L
1661-8734
Publication state
Published
Issued date
2013
Peer-reviewed
Oui
Volume
106
Number
3
Pages
427-450
Language
english
Abstract
The Lepontine dome represents a unique region in the arc of the Central and Western Alps, where complex fold structures of upper amphibolite facies grade of the deepest stage of the orogenic belt are exposed in a tectonic half-window. The NW-verging Mont Blanc, Aar und Gotthard basement folds and the Lower Penninic gneiss nappes of the Central Alps were formed by ductile detachment of the upper European crust during its Late Eocene–Early Oligocene SE-directed underthrust below the upper Penninic and Austroalpine thrusts and the Adriatic plate. Four underthrust zones are distinguished in the NW-verging stack of Alpine fold nappes and thrusts: the Canavese, Piemont, Valais and Adula zones. Up to three schistosities S1–S3, folds F1–F3 and a stretching lineation XI with top-to-NW shear indicators were developed in the F1–F3 fold nappes. Spectacular F4 transverse folds, the SW-verging Verzasca, Maggia, Ziccher, Alpe Bosa and Wandfluhhorn anticlines and synclines overprint the Alpine nappe stack. Their formation under amphibolite facies grade was related to late ductile folding of the southern nappe roots during dextral displacement of the Adriatic indenter. The transverse folding F4 was followed since 30 Ma by the pull-apart exhumation and erosion of the Lepontine dome. This occurred coevally with the formation of the dextral ductile Simplon shear zone, the S-verging backfolding F5 and the formation of the southern steep belt. Exhumation continued after 18 Ma with movement on the brittle Rhone-Simplon detachment, accompanied by the N-, NW- and W-directed Helvetic and Dauphiné thrusts. The dextral shear is dated by the 29–25 Ma crustal-derived aplite and pegmatite intrusions in the southern steep belt. The cooling by uplift and erosion of the Tertiary migmatites of the Bellinzona region occurred between 22 and 18 Ma followed by the exhumation of the Toce dome on the brittle Rhone–Simplon fault since 18 Ma.
Keywords
Switzerland, Italy, Alpine orogeny, Tertiary fold structures, Gneiss dome, Geochronology
Web of science
Publisher's website
Open Access
Yes
Create date
16/07/2018 15:58
Last modification date
01/10/2019 7:17
Usage data