Benchmarking analogue models of brittle thrust wedges

This paper gives an overview of the large-scale tectonic styles encountered in orogens worldwide. Thin-skinned and thick-skinned tectonics represent two end member styles recognized in mountain ranges. Both styles are encountered in former passive 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 most orogens thick-skinned and thin-skinned structures both occur and evolve with a pattern where nappe stacking propagates outward and downward.

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“…Supplementary Materials: The following are available online at www.mdpi.com/2076-3263/7/3/71/s1 [311][312][313][314][315][316][317][318].…”

Section: Discussionmentioning

confidence: 99%

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

Pfiffner

2017

Geosciences

125

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“…Goren et al, 2008), buoyancy-driven subduction models (e.g. Jacoby, 1973;Kincaid and Olson, 1987;Funiciello et al, 2003Funiciello et al, , 2006Funiciello et al, , 2008Schellart, 2004aSchellart, , 2008Schellart, , 2010aBellahsen et al, 2005;Guillaume et al, 2009Guillaume et al, , 2010Duarte et al, 2013;Strak and Schellart, 2014;Chen et al, 2015aChen et al, ,b, 2016, buoyancy-driven continental subduction experiments (e.g. Edwards et al, 2015), and experiments investigating Rayleigh-Taylor instabilities (e.g.…”

Section: Internal Approachmentioning

confidence: 99%

“…In the last decade, the reproducibility of analogue models has been under investigation with benchmark studies of upper crustal shortening and extension , and upper crustal shortening (Schreurs et al, 2016). Such studies provide new insight into the influence of a variety of conditions (e.g.…”

Section: Introductionmentioning

confidence: 99%

A review of analogue modelling of geodynamic processes: Approaches, scaling, materials and quantification, with an application to subduction experiments

Schellart

Strak

2016

Journal of Geodynamics

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132

105

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a b s t r a c tWe present a review of the analogue modelling method, which has been used for 200 years, and continues to be used, to investigate geological phenomena and geodynamic processes. We particularly focus on the following four components: (1) the different fundamental modelling approaches that exist in analogue modelling; (2) the scaling theory and scaling of topography; (3) the different materials and rheologies that are used to simulate the complex behaviour of rocks; and (4) a range of recording techniques that are used for qualitative and quantitative analyses and interpretations of analogue models. Furthermore, we apply these four components to laboratory-based subduction models and describe some of the issues at hand with modelling such systems. Over the last 200 years, a wide variety of analogue materials have been used with different rheologies, including viscous materials (e.g. syrups, silicones, water), brittle materials (e.g. granular materials such as sand, microspheres and sugar), plastic materials (e.g. plasticine), viscoplastic materials (e.g. paraffin, waxes, petrolatum) and visco-elasto-plastic materials (e.g. hydrocarbon compounds and gelatins). These materials have been used in many different set-ups to study processes from the microscale, such as porphyroclast rotation, to the mantle scale, such as subduction and mantle convection. Despite the wide variety of modelling materials and great diversity in model set-ups and processes investigated, all laboratory experiments can be classified into one of three different categories based on three fundamental modelling approaches that have been used in analogue modelling: (1) The external approach, (2) the combined (external + internal) approach, and (3) the internal approach. In the external approach and combined approach, energy is added to the experimental system through the external application of a velocity, temperature gradient or a material influx (or a combination thereof), and so the system is open. In the external approach, all deformation in the system is driven by the externally imposed condition, while in the combined approach, part of the deformation is driven by buoyancy forces internal to the system. In the internal approach, all deformation is driven by buoyancy forces internal to the system and so the system is closed and no energy is added during an experimental run. In the combined approach, the externally imposed force or added energy is generally not quantified nor compared to the internal buoyancy force or potential energy of the system, and so it is not known if these experiments are properly scaled with respect to nature. The scaling theory requires that analogue models are geometrically, kinematically and dynamically similar to the natural prototype. Direct scaling of topography in laboratory models indicates that it is often significantly exaggerated. This can be ascribed to (1) The lack of isostatic compensation, which causes topography to be too high.(2) The lack of erosion, which causes topography to be too high....

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“…Analog sandbox experiments have been used extensively to study the dynamics of accretionary prisms (for recent reviews, see Buiter, ; Graveleau et al, ; Schreurs et al, ). Sandbox experiments are often performed in subaerial (dry) conditions, that is,

λ^{*} = 0

, and the sands used in experiments are estimated to have a weakening factor

χ \approx 2 - 26 %

if the difference between peak and reactivation friction coefficient is considered, or

χ \approx 10 - 44 %

if instead the difference between peak and dynamic friction coefficient is considered (Klinkmüller et al, ) (Figure ).…”

Section: Discussionmentioning

confidence: 99%

Control of Fault Weakening on the Structural Styles of Underthrusting‐Dominated Non‐Cohesive Accretionary Wedges

2020

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Underthrusting is a typical process at compressive margins responsible for nappe stacking and sediment subduction. In nature, underthrusting is often associated with weak basal faults, although static mechanical analysis (critical taper theory) suggests that weak basal faults promote accretion while strong basal faults promote underthrusting. We perform mathematical analyses and numerical simulations to determine whether permanent fault weakening promotes or inhibits underthrusting. We investigate the control of permanent fault weakening on the dynamics of a strong‐based ( false(1−λb*false)μb≈false(1−λ*false)μ) non‐cohesive wedge ( μ and μb are internal and basal friction, respectively). We control the wedge material strength by a spatially constant fluid overpressure factor ( λ*), and fault strength by a plastic strain weakening factor ( χ). First, we use the critical taper theory to determine a mechanical mode diagram that predicts structural styles. Then, we perform numerical simulations of accretionary wedge formation to establish their dynamical structural characteristics. We determine a continuum of structural styles between three end‐members which correspond to the theoretical mechanical mode transitions. Style 1 is characterized by thin tectonic slices and little to no underthrusting. Style 2 shows thick slices, nappe stacking, and shallow gravity‐driven tectonics. Style 3 displays the complete underthrusting of the incoming sediments, that are exhumed when they reach the backstop. We conclude that in the condition of an initially strong wedge base, permanent fault weakening promotes underthrusting. Thus, this contribution enlightens the control of the dynamic evolution of material properties on the formation of subduction channels, slope instabilities, and antiformal nappe stacks.

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Benchmarking analogue models of brittle thrust wedges

Abstract: Please note that this is an author-produced PDF of an article accepted for publication following peer review. The definitive publisher-authenticated version is available on the publisher Web site.

Cited by 68 publications

References 27 publications

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

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

A review of analogue modelling of geodynamic processes: Approaches, scaling, materials and quantification, with an application to subduction experiments

Control of Fault Weakening on the Structural Styles of Underthrusting‐Dominated Non‐Cohesive Accretionary Wedges

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