Numerical models for the control of inherited basin geometries on structures and emplacement of the Klippen nappe (Swiss Prealps)

Wissing, S.B; Pfiffner, Othmar-Adrian

doi:10.1016/s0191-8141(02)00159-1

Cited by 23 publications

(8 citation statements)

References 26 publications

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“…Geological reconstructions of the Helvetic nappe system showed the correlation of the nappes with their original positions along the pre-Alpine European passive margin, which was characterized by half-grabens and horsts (e.g., Epard, 1990;Boutoux et al, 2014). In agreement with previous modeling studies (e.g., Beaumont et al, 2000;Wissing and Pfiffner, 2003;Bellahsen et al, 2012;Lafosse et al, 2016;Bauville and Schmalholz, 2017), our results suggest that tectonic inheritance in the form of half-grabens and horsts has a strong impact on the development of fold and thrust nappes during crustal deformation. Our results indicate that two types of tectonic inheritance are important, namely the geometry and the magnitude of mechanical heterogeneities.…”

Section: Tectonic Inheritance Mechanical Heterogeneities and Potentisupporting

confidence: 93%

“…Therefore, the geometrical structure and kinematic evolution of the Helvetic nappe system is reasonably well understood. There are also theoretical and analogue modeling studies investigating the formation of fold-and-thrust belts and nappes (e.g., Bucher, 1956;Rubey and King Hubbert, 1959;Dietrich and Casey, 1989;Merle, 1989;Casey and Dietrich, 1997;Wissing and Pfiffner, 2003;Bauville et al, 2013;Poulet et al, 2014;Erdős et al, 2014;Jaquet et al, 2014;Ruh et al, 2014;Bauville and Schmalholz, 2017). However, the controlling physical processes of nappe detachment, transport and stacking, and the associated dominant rock deformation mechanism are still disputed.…”

Section: Introductionmentioning

confidence: 99%

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Tectonic inheritance controls nappe detachment, transport and stacking in the Helvetic nappe system, Switzerland: insights from thermomechanical simulations

2020

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Abstract. Tectonic nappes have been investigated for more than a hundred years. Although geological studies often refer to a “nappe theory”, the physical mechanisms of nappe formation are still disputed. We apply two-dimensional numerical simulations of shortening of a passive margin to investigate the thermomechanical processes of detachment (or shearing off), transport and stacking of nappes. We use a visco-elasto-plastic model with standard creep flow laws, Drucker–Prager and von Mises yield criteria. We consider tectonic inheritance with two initial mechanical heterogeneities: (1) lateral heterogeneity of the basement–cover interface due to half-grabens and horsts and (2) vertical heterogeneities due to layering of mechanically strong and weak sedimentary units. The model shows detachment and horizontal transport of a thrust nappe that gets stacked on a fold nappe. The detachment of the thrust sheet is triggered by stress concentrations around the sediment–basement contact and the resulting brittle–plastic shear band that shears off the sedimentary units from the sediment–basement contact. Horizontal transport is facilitated by a basal shear zone just above the basement–cover contact, composed of thin, weak sediments that act as a décollement. Fold nappe formation occurs by a dominantly ductile closure of a half-graben and the associated extrusion of the half-graben fill. We apply our model to the Helvetic nappe system in western Switzerland, which is characterized by stacking of the Wildhorn thrust nappe above the Morcles fold nappe. The modeled structures, the deformation rates and the temperature field agree with data from the Helvetic nappe system. Mechanical heterogeneities must locally generate effective viscosity (i.e., ratio of stress to viscoplastic strain rate) contrast of about 3 orders of magnitude to model nappe structures similar to the ones of the Helvetic nappe system. Our results indicate that the structural evolution of the Helvetic nappe system was controlled by tectonic inheritance and that material softening mechanisms are not essential to reproduce the first-order nappe structures.

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Section: Tectonic Inheritance Mechanical Heterogeneities and Potentisupporting

confidence: 93%

Section: Introductionmentioning

confidence: 99%

Tectonic inheritance controls nappe detachment, transport and stacking in the Helvetic nappe system, Switzerland: insights from thermomechanical simulations

2020

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“…In agreement with previous modelling studies (e.g. Beaumont et al, 2000;Wissing and Pfiffner, 2003;Bellahsen et al, 2012;Lafosse et al, 2016;Bauville and Schmalholz, 2017), our results suggest that tectonic inheritance in the crust in the form of half-grabens and horsts has a strong impact on the development of fold and thrust nappes during crustal deformation.…”

Section: Tectonic Inheritance Mechanical Heterogeneities and Potentisupporting

confidence: 93%

Towards a nappe theory: Thermo-mechanical simulations of nappe detachment, transport and stacking in the Helvetic Nappe System, Switzerland

Kiss¹,

Duretz²,

Schmalholz³

2019

Preprint

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Abstract. Tectonic nappes are observed for more than a hundred years. Although geological studies often refer to a nappe theory, the physical mechanisms of nappe formation are still incompletely understood. We apply two-dimensional numerical simulations of shortening of a passive margin, to investigate the thermo-mechanical processes of detachment, transport and stacking of nappes. We use a visco-elasto-plastic model with standard creep flow laws and Drucker-Prager yield criterion. We consider tectonic inheritance with two initial mechanical heterogeneities: (1) lateral heterogeneity of the basement-cover interface due to half-grabens and horsts and (2) vertical heterogeneities due to layering of mechanically strong and weak sedimentary units. The model shows detachment and horizontal transport of a thrust nappe and stacking of this thrust nappe above a fold nappe. The detachment of the thrust sheet is triggered by stress concentrations around the sediment-basement contact and the resulting brittle-plastic shear band formation. The horizontal transport is facilitated by a basal shear zone just above the basement-cover contact, composed of thin, weak sediments. Fold nappe formation occurs by a dominantly ductile closure of a half-graben and the associated extrusion of the half-graben fill. We apply our model to the Helvetic nappe system in Western Switzerland, which is characterized by stacking of the Wildhorn thrust nappe above the Morcles fold nappe. The modeled structures and temperature field agree with data from the Helvetic nappe system. The mechanical heterogeneities must generate contrasts in effective viscosity (i.e. ratio of stress to strain rate) of four orders of magnitude to model nappe structures similar to the ones of the Helvetic nappe system.

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“…As a result sedimentary strata with different mechanical behavior may be juxtaposed and act as lateral heterogeneity in the course of subsequent horizontal compression and detachment. Numerical experiments by [41] suggest that folds develop preferentially at such heterogeneities.…”

Section: Role Of Pre-existing Normal Faultsmentioning

confidence: 99%

Thick-Skinned and Thin-Skinned Tectonics: A Global Perspective

Pfiffner¹

2017

Preprint

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This paper gives an overview of the large-scale tectonic styles encountered in orogens worldwide. Thin-skinned and thick-skinned tectonics represents two end member styles recognized in mountain ranges. A thick-skinned tectonic style is typical for margins of continental plates. Thick-skinned style including the entire crust and possibly the lithospheric mantle are associated with intracontinental contraction. Delamination of subducting continental crust and horizontal protrusion of upper plate crust into the opening gap occurs in the terminal stage of continent-continent collision. Continental crust thinned prior to contraction is likely to develop relatively thin thrust sheets of crystalline basement. A true thin-skinned type requires a detachment layer of sufficient thickness. Thickness of the décollement layer as well as the mechanical contrast between décollement layer and detached cover control the style of folding and thrusting within the detached cover units. In subduction related orogens, thin-and thick-skinned deformation may occur several hundreds of kilometers from the plate contact zone. Basin inversion resulting from horizontal contraction may lead to the formation of basement uplifts by the combined reactivation of pre-existing normal faults and initiation of new reverse faults. In composite orogens thick-skinned and thin-skinned structures evolve with a pattern where nappe stacking propagates outward and downward.

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Numerical models for the control of inherited basin geometries on structures and emplacement of the Klippen nappe (Swiss Prealps)

Cited by 23 publications

References 26 publications

Tectonic inheritance controls nappe detachment, transport and stacking in the Helvetic nappe system, Switzerland: insights from thermomechanical simulations

Tectonic inheritance controls nappe detachment, transport and stacking in the Helvetic nappe system, Switzerland: insights from thermomechanical simulations

Towards a nappe theory: Thermo-mechanical simulations of nappe detachment, transport and stacking in the Helvetic Nappe System, Switzerland

Thick-Skinned and Thin-Skinned Tectonics: A Global Perspective

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