Fold nappes; Numerical modeling; Western Swiss Alps; Nappe; fold nappe; folding; finite element method; Morcles nappe; structural geology; tectonics
Von Tscharner Marina, Schmalholz Stefan, Epard Jean-Luc (2016), 3-D numerical models of viscous flow applied to fold nappes and the Rawil depression in the Helvetic nappe system (western Switzerland), in Journal of Structural Geology
, 86, 32-46.
Von Tscharner Marina, Schmalholz Stefan (2015), A 3-D Lagrangian finite element algorithm with remeshing for simulating large-strain hydrodynamic instabilities in power law viscoelastic fluids, in Geochemistry Geophysics Geosystems
, 16, 215-245.
Bauville Arthur, Schmalholz Stefan (2015), Transition from thin- to thick-skinned tectonics and consequences for nappe formation: numerical simulations and applications to the Helvetic nappe system, Switzerland, in Tectonophysics
, 665, 101-117.
Von Tscharner Marina, Schmalholz Stefan, Duretz Thibault (2014), Three-dimensional necking during viscous slab detachment, in Geophysical Research Letters
, 41, 4194-4200.
Bauville Arthur, Schmalholz Stefan (2013), Thermo-mechanical model for the finite strain gradient in kilometer-scale shear zones, in Geology
, 41(March), 567-570.
Bauville Arthur, Epard Jean-Luc, Schmalholz Stefan M., A simple thermo-mechanical shear model applied to the Morcles fold nappe (Western Alps), in Tectonophysics
Fold nappes are large recumbent folds with amplitudes of sometimes more than 10 kilometers. The aims of this project are to improve our understanding of (1) the dynamics of fold nappe formation in general and (2) the tectonic evolution of the fold nappes in the Western Swiss Alps. Although fold nappes are prominent geological structures in the Western Swiss Alps and in other mountain ranges and field work and data analysis has been performed since more than 100 years, the basic mechanisms by which fold nappes form are still not understood. In this project the mathematical equations of continuum mechanics are solved with numerical algorithms to study the dynamics of fold nappe formation. The different numerical algorithms applied in this project are based on the finite element method and can simulate (1) ductile (i.e. Newtonian viscous or power-law rheology) rock deformation in 2D and 3D, and (2) the thermo-mechanical processes acting during continental lithosphere deformation in 2D. The numerical results will be compared with already available and with during this project newly collected field data. Data, such as nappe geometry, shear sense orientation or finite strain ellipsoid, are available from both the numerical simulations and field work and will be saved in a common data base to allow a direct and quantitative comparison. The results of this comparison are used to adjust the numerical models (e.g. boundary conditions, initial geometry or material parameters) in order to provide numerical simulations of fold nappe formation which agree as good as possible with the basic field data (e.g. nappe geometry, finite strain pattern or distribution of metamorphic grade). To improve the understanding of fold nappe dynamics this project focuses on three main topics: (1) the 2D large strain formation of recumbent folds, including parasitic folds, in ductile multilayers under a combination of simple and pure shear with application to the Morcles nappe, (2) the 2D formation of basement fold nappes and the thermo-mechanical conditions controlling folding versus faulting (i.e. thrusting) of basement-cover sequences with application to the Antigorio nappe and (3) the formation of ductile fold nappes in 3D focusing on fold-axis parallel strain and fold-axis deformation with application to the Morcles-Doldenhorn nappe. Three different and well-established leading-edge numerical algorithms are available for this project and will be applied, elaborated and adjusted to perform the simulations. The numerical simulations will be performed on a high-end computational cluster which is also available for this project. The theoretical modeling work is accompanied by field work and structural analysis which will focus on field areas where (1) existing data is controversial, sparse or unclear and (2) numerical results differ significantly from existing data. We request three PhD students to perform this study, integrating computational tectonics with geological field work and structural analysis. The results of this project will improve our understanding of mountain building processes and the deformation of the Earth’s crustal rocks. The project involves collaboration with other scientists of the Faculty of Geosciences and Environment at the University of Lausanne and will strengthen the already established collaboration with the Department of Earth Sciences at the ETH Zurich.