Large vertical displacements of a crystalline massif recorded by Raman thermometry

Nibourel, Lukas; Berger, Alfons; Egli, Daniel; Luensdorf, Nils K.; Herwegh, Marco

doi:10.1130/g45121.1

Cited by 30 publications

(69 citation statements)

References 13 publications

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“…This suggests that distributed shortening occurred at the temperature peak as also suggested for the Mont Blanc ECM (Boutoux et al, ). Similar studies relating the tectonic and the thermal structure in the Helvetic nappes were also performed by Groshong et al (), Herwegh and Pfiffner (), and Nibourel et al ().…”

Section: Introductionsupporting

confidence: 74%

The 3‐D Thermal Structure of the Helvetic Nappes of the European Alps: Implications for Collisional Processes

et al. 2020

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Understanding the rheology of orogenic wedges requires the knowledge of the structural and thermal evolution of collisional units. In this study, we document the maximum temperature reached by the sedimentary cover nappes of the External Crystalline Massif (Western and central Alps) by Raman spectroscopy of carbonaceous material, between the Belledonne (France) and the Aar (Switzerland) Massifs. These cover units form the Helvetic/Dauphinois nappe complex. Maximum temperatures reached by the Upper Helvetic nappes lie in a range spanning from below 220 and 350°C ± 50°C. For the Lower Helvetic nappes, the temperatures spread between 226 and 358°C ± 50°C. These temperatures were projected on two structural cross sections in order to constrain the 3-D thermal structure. From these data, we propose that the Helvetic nappes were deformed and emplaced before and/or during the thermal peak, which supports recent findings that shortening in the External Crystalline Massif was mainly accommodated during a 5-to 10-Myr-long thermal peak before deformation localized along crustal thrusts, which exhumed and cooled down the wedge. During this late exhumation, the isotherms corresponding to the thermal peak were passively folded.

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Section: Introductionsupporting

confidence: 74%

The 3‐D Thermal Structure of the Helvetic Nappes of the European Alps: Implications for Collisional Processes

et al. 2020

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“…It is possible to compare potential source compositions to the detrital ones because the potential source rocks were already narrowed down to particular regions based on other provenance proxies and because many of these rocks are still preserved in the Alpine chain today. For comparison we used detrital data from Stutenbecker et al (2017) as well as published source rock data from different units across the Central Alps (Steck and Burri, 1971;Chinner and Dixon, 1973;Ernst and Dal Piaz, 1978;Hunziker and Zingg, 1980;Oberhänsli, 1980;Sartori, 1990;Thélin et al, 1990;Reinecke, 1998;von Raumer et al, 1999;Cartwright and Barnicoat, 2002;Bucher and Bousquet, 2007;Angiboust et al, 2009;Bucher and Grapes, 2009;Weber and Bucher, 2015).…”

Section: Sampling Strategy and Methodologymentioning

confidence: 99%

Miocene basement exhumation in the Central Alps recorded by detrital garnet geochemistry in foreland basin deposits

Stütenbecker¹,

Tollan

Madella³

et al. 2019

Solid Earth

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Abstract. The Neogene evolution of the European Alps was characterized by the exhumation of crystalline basement, the so-called external crystalline massifs. Their exhumation presumably controlled the evolution of relief, distribution of drainage networks, and generation of sediment in the Central Alps. However, due to the absence of suitable proxies, the timing of their surficial exposure and thus the initiation of sediment supply from these areas are poorly constrained. The northern Alpine foreland basin preserves the Oligocene to Miocene sedimentary record of tectonic and climatic adjustments in the hinterland. This contribution analyses the provenance of 25 to 14 Myr old alluvial fan deposits by means of detrital garnet chemistry. Unusually grossular- and spessartine-rich garnet is found (1) to be a unique proxy for identifying detritus from the external crystalline massifs and (2) to occur abundantly in ca. 14 Myr old deposits of the foreland basin. In contrast to previous assumptions, we therefore propose that the external massifs were already exposed to the surface ca. 14 Myr ago.

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“…Further improvements could be made by adjusting the initial geothermal gradient or by modifying the initial geometrical configuration. For the latter case, primarily,Nibourel et al (2018) demonstrate that 560 the Aar massif experienced a 10 − 15 • southwards dip in relation to the isotherms. Essentially such a configuration would, for example, place the half-graben system further up in the isotherms.…”

mentioning

confidence: 83%

“…The onset of Alpine burial of the proto-nappe system is constrained by the last deposited sediments with ages of ca. 28 to 95 34 Ma (Kirschner et al, 1995;Nibourel et al, 2018). Peak metamorphic conditions in the Helvetic nappe system occurred between ca.…”

mentioning

confidence: 98%

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Control of 3D tectonic inheritance on fold-and-thrust belts: insights from 3D numerical models and application to the Helvetic nappe system

Spitz¹,

Bauville²,

Epard³

et al. 2019

Preprint

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Fold-and-thrust belts and associated tectonic nappes are common in orogenic regions. They exhibit a wide variety of geometries and often a considerable along-strike variation. However, the mechanics of fold-and-thrust belt formation and the control of the initial geological configuration on this formation are still incompletely understood. Here, we apply three-dimensional (3D) thermo-mechanical numerical simulations of the shortening of the upper crustal region of a passive margin to investigate 5 the control of 3D laterally variable inherited structures on the fold-and-thrust belt evolution and associated nappe formation.We consider tectonic inheritance by applying an initial model configuration with horst and graben structures having laterally variable geometry and with sedimentary layers having different mechanical strength. We use a visco-plastic rheology with temperature dependent flow laws and a Drucker-Prager yield criterion. The models show the folding, detachment and horizontal displacement of sedimentary units, which resemble structures of fold and thrust nappes. The models further show the stacking 10 of nappes. The detachment of nappe-like structures is controlled by the initial basement and sedimentary layer geometry.Significant horizontal transport is facilitated by weak sedimentary units below these nappes. The initial half-graben geometry has a strong impact on the basement and sediment deformation. Generally, deeper half-grabens generate thicker nappes and stronger deformation of the neighboring horst while shallower half-grabens generate thinner nappes and less deformation in the horst. Horizontally continuous strong sediment layers, which are not restricted to inital graben structures, cause detachment 15 folding and not overthrusting. The amplitude of the detachment folds is controlled by the underlying graben geometry. A mechanically weaker basement favors the formation of fold nappes while stronger basement favors thrust sheets. The applied model configuration is motivated by the application of the 3D model to the Helvetic nappe system of the French-Swiss Alps.Our model is able to reproduce several first-order structural features of this nappe system, namely (i) closure of a half-graben and associated formation of the Morcles and Doldenhorn nappes, (ii) the overthrusting of a nappe resembling the Wildhorn and 20 1 https://doi.Glarus nappes and (iii) the formation of a nappe pile resembling the Helvetic nappes resting above the Infrahelvetic complex.Furthermore, the finite strain pattern, temperature distribution and timing of the 3D model is in broad agreement with data from the Helvetic nappe system. Our model, hence, provides a first-order 3D reconstruction of the tectonic evolution of the Helvetic nappe system based on thermo-mechanical deformation processes.

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Large vertical displacements of a crystalline massif recorded by Raman thermometry

Cited by 30 publications

References 13 publications

The 3‐D Thermal Structure of the Helvetic Nappes of the European Alps: Implications for Collisional Processes

The 3‐D Thermal Structure of the Helvetic Nappes of the European Alps: Implications for Collisional Processes

Miocene basement exhumation in the Central Alps recorded by detrital garnet geochemistry in foreland basin deposits

Control of 3D tectonic inheritance on fold-and-thrust belts: insights from 3D numerical models and application to the Helvetic nappe system

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