Transition from thin- to thick-skinned tectonics and consequences for nappe formation: Numerical simulations and applications to the Helvetic nappe system, Switzerland

摘要: Abstract We use two-dimensional numerical simulations to study the deformation style and formation of nappes during shortening basement–cover systems with half-grabens. perform only linear power-law viscous rheology, also thermo-mechanical viscoelastoplastic rheology temperature-dependent viscosities. The accumulated, area-averaged strain is calculated for sediments, es, basement, eb, quantify style. results show that transition from thin-skinned dominated (es/eb > 1) thick-skinned (es/eb ≤ 1) controlled by two effective viscosity ratios: ratio at top basement bottom sedimentary cover. A higher basement-internal favors whereas a deformation. Simulations same first-order as simulations. further fold nappe associated thrust Fold are formed shearing extrusion sediments closure half-grabens due shearing-off which nearly undeformed. applied Morcles Helvetic system, Switzerland.