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Fossil-bearing shale specimens that include sulfides in their compositions are chemically reactive and sometimes also mechanically fragile. This decay is often related to iron sulfate efflorescence resulting from the oxidation of sulfide compounds. The processes underlying these degradations are poorly known, thus impeding the elaboration of curative or preventive treatments. The present contribution aims to identify the origin of museum specimen alterations. It focuses on the Flouest collection housed at the Muséum National d’Histoire Naturelle (MNHN, Paris, France) and originating from the Autun Basin (Saône-et-Loire, France, Permian). To evaluate the alteration of MNHN specimens, it appeared necessary to compare their composition with that of unaltered shale so as to identify chemical changes occurring during ageing. Therefore, new material was collected in the Autun Basin, among others on the locality of Muse that corresponds to the same lithostratigraphic unit as that of the MNHN specimens. This material was, if necessary, artificially aged. The first part of this work, presented elsewhere, deals with the use of X-ray diffraction and Mössbauer spectroscopy for characterizing iron reactivity and speciation. It leads to the conclusion that the reactivity of iron in the shale matrix was limited and could not account for the large efflorescence of iron (II) sulfate occurring nearby the fossil. The second part presented here focuses on the use of S K-edge X-ray Absorption Near Edge Structure (XANES) spectroscopy for characterizing sulfur speciation and reactivity. Measurements were performed on the shale matrix and on thin layers of maceral found in the proximity of damaged areas. As sulfur may be found in association with calcium or organic matter, complementary techniques were implemented, such as FTIR spectroscopy, Rock-Eval pyrolysis (characterization of organic matter content) and Ca K-edge XANES (analysis of calcium speciation) spectroscopy. It was shown that sulfur is mainly related to thioether, sulfoxide, iron sulfide, and sulfates whereas calcium is mainly bound to carboxylate, carbonate and/or sulfate groups. FTIR analysis of the macerals confirmed the presence of vitrinite on damaged MNHN specimens. The low oxygen content of new shale samples determined by Rock-Eval pyrolysis indicates that the organic matter is well preserved, despite the fact that samples come from outcrop surface. In the newly collected material, sulfur is mainly related to organic sulfides (thioether) with a minor occurrence of iron sulfide. In the shale fraction of damaged MNHN specimens, sulfur is mostly oxidized into a mixture of iron and calcium sulfate. However, in the vitrinite layers of the same specimens, a large proportion of sulfur corresponds to organic sulfides. Also the oxidation of sulfur does not occur homogeneously but preferentially in the shale fraction, probably because this latter is porous whereas vitrinite is not. Artificial ageing of new shale material showed that the oxidation of organic sulfides could be reproduced at 90 °C, 80% of relative humidity. However, the obtained efflorescence almost exclusively corresponds to calcium sulfate whereas iron (II) sulfates are mostly observed on MNHN specimens. The new material collected on site is probably to be questioned, and future studies will have to select new samples with fossil remains. This will be the object of the third part of this work. [ABSTRACT FROM AUTHOR]

This article presents the numerical implementation of an elastoplastic behavior model suitable for estimating the damage produced when excavating galleries in deep argilite layers. The main rheological features of the model are related to post-peak behavior, brittle fracture, softening and dilatancy effects. Damage of the rock may increase significantly the hydraulic permeability and vice versa. We focus on numerical difficulties such as suitable calculations for plastic flow at very low confinement levels and those resulting from following the confinement factor in such a way that the algorithms converge until physical collapse. The numerical results obtained with a 2D simulation are in good agreement with generally observed phenomena. Dilatancy produces instantaneous cohesion, which disappears with time. Increasing permeability speeds up this tendency. [Copyright &y& Elsevier]

In the Mont Terri Rock Laboratory, eleven organisations from six countries (ANDRA and IPSN from France) are investigating jointly a Mesozoic shale formation, the Opalinus Clay. The aims of the research programme are to analyse its hydrogeological, geochemical and rock mechanical properties, the changes induced by the excavation of galleries, by heat-generating waste and by engineered barriers, and to evaluate and improve appropriate investigation techniques. The results of a series of experiments indicate that, at a convenient site, the investigated or similar clay formations could be favourable for hosting a safe repository for radioactive waste. To cite this article: M. Thury, C. R. Physique 3 (2002) 923–933. [ABSTRACT FROM AUTHOR]

The Lesueur landslide occurred on 3 September 1963 on the outside of a meander of the North Saskatchewan River in northeast Edmonton. The displaced volume was 0.76 Mm[sup 3] of Pleistocene deposits and underlying Upper Cretaceous mudstones. The trigger of the landslide is believed to be accelerated erosion of the slope toe caused by dumping of mine waste on the inside of the meander. Surveys in 1964, 1971, 1992, 1995, 1997, and 1998 have documented continued slope movements. The main scarp grew in height from 7.5 m on 4 September 1963 to 13.9 m in 1995 but retrogressed only 3 m. The displaced material extended up to 24 m into the North Saskatchewan River. When the forward motion of the passive block of the translational slide ceased to be driven by the sinking of the active block, river erosion caused rotational sliding of the displaced material on the surface of separation.Key words: landslide, Edmonton, Cretaceous, mudstone, erosion, North Saskatchewan River.Le glissement de Lesueur s'est produit le 3 septembre 1963 sur l'extérieur d'un méandre de la rivière North Saskatchewan au nord est de Edmonton. Le volume déplacé était de 0,76 Mm[sup 3] de dépôts du Pléistocène et d'argilites sous-jacents du Crétacée supérieur. On croit que le facteur déclencheur du glissement est l'érosion accélérée du talus causée par le déversement de résidus miniers à l'intérieur du méandre. Des relevés en 1964, 1971, 1992, 1995, 1997, et 1998 ont documenté des mouvements continuels du talus. La principale cicatrice s'est accrue en hauteur de 7,5 m le 4 septembre 1963 à 13,9 m en 1995, mais a rétrogressé de seulement 3 m. Lorsque le mouvement vers l'avant du bloc de butée du glissement de translation résultant de l'enfoncement du bloc de poussée a cessé de se produire, l'érosion de la rivière a causé un mouvement de glissement en rotation du matériau déplacé sur la surface de séparation.Mots clés : glissement, Edmonton, Crétacée, argilite, érosion, rivière North Saskatchewan.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]