Litho- and biostratigraphy of the Opalinus Clay and bounding formations in the Mont Terri rock laboratory (Switzerland)

Hostettler, Bernhard; Reisdorf, Achim G.; Jaeggi, David; Deplazes, Gaudenz; Bläsi, Hansruedi; Morard, Alain; Feist-Burkhardt, Susanne; Waltschew, Anton; Dietze, Volker; Menkveld-Gfeller, Ursula

doi:10.1007/s00015-016-0250-3

Cited by 43 publications

(43 citation statements)

References 9 publications

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“…This led to more detailed lithostratigraphic, hydrogeological, and geochemical descriptions of this formation (Schaeren and Norbert 1989;Tripet et al 1990;Blaesi et al 1991Blaesi et al , 1996Gautschi et al 1993;Hostettler et al 2017). Not only the discovery of the Opalinus Clay at this locality, but also the simple geometry (limited thrust zones and imbricates) and the possibility of horizontal access, led to establishing the Mont Terri rock laboratory.…”

Section: Lithofaciesmentioning

confidence: 94%

“…One of the first lithological descriptions of the Opalinus Clay was given by Schmidt et al (1924) from a borehole near Buix, located about 20 km to the NW of Mont Terri, where a total Glovelier St-Ursanne Courgenay M o n t T e rr i tu n n e l V o rb o u rg a n tic lin e M o n t R u s s e li n tu n n e l M o n t T e rr i a n ti c li n e Mont Terri rock laboratory C la ir m o n t a n t ic li n e C lo s d u D o u b s a n ti c li n e C a q u e r e ll e a n ti c li n e M o n t T e r r i a n t ic li n e thickness of 157.5 m was encountered. The present thickness of the Opalinus Clay in the Mont Terri rock laboratory has been estimated to be 131 m. This corresponds to a sedimentary thickness of about 120 m when corrected for tectonic overthrusting (Hostettler et al 2017). The Opalinus Clay at Mont Terri is an overconsolidated claystone.…”

Section: Site Characteristicsmentioning

confidence: 95%

“…The Opalinus Clay 2 consists of a monotonous sequence of dark grey, silty, micaceous clays and sandy shales, deposited around 174 Ma ago. This age is based on a new stratigraphic investigation in a deep borehole cutting the Opalinus Clay and adjacent formations near the rock laboratory (Hostettler et al 2017). The Opalinus Clay is overlain by the Passwang Formation of sandy limestones, shales and oolitic ironstones, and underlain by the Staffelegg Formation consisting of limestones, marls, and shaly intercalations (see geologic map of Fig.…”

Section: Site Characteristicsmentioning

confidence: 99%

“…Schaeren and Norbert (1989) and Blaesi et al (1991) defined the base of the Opalinus Clay as a lithological transition of argillaceous sediments to more marly sediments. The latter have been identified as the Gross Wolf Member of the Staffelegg Formation (Reisdorf et al 2011;Hostettler et al 2017). The upper boundary of the Opalinus Clay is defined by a distinct hardground of chamositic crusts (Blaesi et al 1991) and iron oolites.…”

Section: Lithofaciesmentioning

confidence: 99%

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Mont Terri rock laboratory, 20 years of research: introduction, site characteristics and overview of experiments

Bossart¹,

et al. 2017

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Geologic repositories for radioactive waste are designed as multi-barrier disposal systems that perform a number of functions including the long-term isolation and containment of waste from the human environment, and the attenuation of radionuclides released to the subsurface. The rock laboratory at Mont Terri (canton Jura, Switzerland) in the Opalinus Clay plays an important role in the development of such repositories. The experimental results gained in the last 20 years are used to study the possible evolution of a repository and investigate processes closely related to the safety functions of a repository hosted in a clay rock. At the same time, these experiments have increased our general knowledge of the complex behaviour of argillaceous formations in response to coupled hydrological, mechanical, thermal, chemical, and biological processes. After presenting the geological setting in and around the Mont Terri rock laboratory and an overview of the mineralogy and key properties of the Opalinus Clay, we give a brief overview of the key experiments that are described in more detail in the following research papers to this Special Issue of the Swiss Journal of Geosciences. These experiments aim to characterise the Opalinus Clay and estimate safetyrelevant parameters, test procedures, and technologies for repository construction and waste emplacement. Other aspects covered are: bentonite buffer emplacement, highpH concrete-clay interaction experiments, anaerobic steel corrosion with hydrogen formation, depletion of hydrogen by microbial activity, and finally, release of radionuclides Geosci (2017) 110:3-22 DOI 10.1007 into the bentonite buffer and the Opalinus Clay barrier. In the case of a spent fuel/high-level waste repository, the time considered in performance assessment for repository evolution is generally 1 million years, starting with a transient phase over the first 10,000 years and followed by an equilibrium phase. Experiments dealing with initial conditions, construction, and waste emplacement do not require the extrapolation of their results over such long timescales. However, experiments like radionuclide transport in the clay barrier have to rely on understanding longterm mechanistic processes together with estimating safety-relevant parameters. The research at Mont Terri carried out in the last 20 years provides valuable information on repository evolution and strong arguments for a sound safety case for a repository in argillaceous formations.

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Section: Lithofaciesmentioning

confidence: 94%

Section: Site Characteristicsmentioning

confidence: 95%

Section: Site Characteristicsmentioning

confidence: 99%

Section: Lithofaciesmentioning

confidence: 99%

See 2 more Smart Citations

Mont Terri rock laboratory, 20 years of research: introduction, site characteristics and overview of experiments

Bossart¹,

et al. 2017

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show abstract

“…In all figures of this paper, the formations are illustrated by the official colours as defined by the Lithostratigraphic Lexicon. The formation thicknesses in the region of St-Ursanne were adapted after Laubscher (1963a, b) and complemented by the recent borehole BDB-1 for the thicknesses of the Opalinus Clay and Passwang Formation (Hostettler et al 2017).…”

Section: Litho-and Mechanical Stratigraphymentioning

confidence: 99%

Tectonic evolution around the Mont Terri rock laboratory, northwestern Swiss Jura: constraints from kinematic forward modelling

Nussbaum¹,

Kloppenburg²,

Caër

et al. 2017

Swiss J Geosci

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We propose a geometrically, kinematically, and mechanically viable thin-skinned kinematic forward model for a cross section intersecting the Mont Terri rock laboratory in the frontal-most part of the Jura fold-and-thrust belt, Switzerland. In addition to the available tunnel, borehole, and surface data, initial boundary conditions are crucial constraints for the forward modelling scenarios, especially the inherited topography of the basement and any pre-compressional offset within the Mesozoic sediments. Our kinematic analysis suggests an early-stage formation of the Mont Terri anticline located above ENE-trending, Late Paleozoic extensional faults, followed by back-stepping of the deformation developing the Clos du Doubs and Caquerelle anticlines further south. In this model, the thrust sequence was dictated by the inherited basement faults, which acted as nuclei for the ramps, detached along the basal décollement within the Triassic evaporites. The mechanical viability of both the thrust angles and thrust sequence was demonstrated by applying the limit analysis theory. Despite numerous subsurface geological data, extrapolation of structures to depth remains largely under-constrained. We have tested an alternative model for the same cross section, involving an upper detachment at the top of the Staffelegg Formation that leads to duplication of the sub-Opalinus Clay formations, prior to detachment and thrusting on the Triassic evaporites. This model is geometrically and kinematically viable, but raises mechanical questions. A total displacement of 2.9 and 14.2 km are inferred for the classical and the alternative scenarios, respectively. In the latter, forward modelling implies that material was transported 10.8 km along the upper detachment. It is not yet clear where this shortening might have been accommodated. Despite the differences in structural style, both models show that pre-existing basement structures might have interfered in time and space. Both styles may have played a role, with lateral variation dictated by basement inherited structures.

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Geochemical fingerprinting of key lithologies and depositional processes across the upper boundary of the Opalinus Clay (Aalenian, Middle Jurassic, northern Switzerland)

Lauper

Deplazes

Vogel

et al. 2020

The Depositional Record

Self Cite

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The Opalinus Clay is an argillaceous to silty mudstone formation, notable in Switzerland as the selected host rock for deep geological disposal of radioactive waste. Its upper bounding unit (Passwang Formation and eastern equivalents) is composed of successions of mudstone, sandy bioclastic marl and limestone separated by ooidal ironstone beds. The lithostratigraphic transition is diachronous across northern Switzerland and shows high vertical and lateral lithological variability. To constrain this variability into predictive models, and to identify horizons with properties that could potentially influence radionuclide mobility, the sedimentological and diagenetic processes involved in the genesis of this transition have to be investigated. The present study aims at testing the applicability of X‐ray fluorescence chemostratigraphy to characterise the mixed carbonate–siliciclastic units and understand the complex genesis of the lithostratigraphic transition from the Opalinus Clay towards its upper bounding unit. Sediment drill cores from four locations across northern Switzerland (Mont Terri, Riniken, Weiach and Benken) are analysed using high‐resolution X‐ray fluorescence core scanning. Data are compared to petrographic and additional geochemical data sets (inductively coupled plasma mass spectrometry, scanning electron microscopy with energy dispersive X‐ray analysis, micro‐X‐ray fluorescence mapping) obtained from powdered samples, thin section analyses and drill core slabs. The results demonstrate that the combination of these rapid and non‐destructive measurements along with multivariate data analysis allows the fast and objective classification of lithofacies along complex sedimentary successions. Moreover, it provides quantitative means for differentiating between prominent depositional and post‐depositional processes. The lithostratigraphic transition has been traced by the use of specific elemental proxies as a discontinuity, and its genesis linked to sediment bypassing.

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Litho- and biostratigraphy of the Opalinus Clay and bounding formations in the Mont Terri rock laboratory (Switzerland)

Cited by 43 publications

References 9 publications

Mont Terri rock laboratory, 20 years of research: introduction, site characteristics and overview of experiments

Mont Terri rock laboratory, 20 years of research: introduction, site characteristics and overview of experiments

Tectonic evolution around the Mont Terri rock laboratory, northwestern Swiss Jura: constraints from kinematic forward modelling

Geochemical fingerprinting of key lithologies and depositional processes across the upper boundary of the Opalinus Clay (Aalenian, Middle Jurassic, northern Switzerland)

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