Caractérisation du transport de l'oxygène dans des électrolytes céramiques de l'échelle atomique à l'échelle macroscopique

oral invitéNational audienceDes outils tels que la spectroscopie d'absorption X (EXAFS/XANES), la diffraction des neutrons, la spectrométrie d'impédance, l'échange isotopique, la mesure de flux de semi-perméabilité permettent de sonder le transport de l'oxygène sur différentes échelles. Ces techniques ont été appliquées à deux familles de conducteurs par ions oxyde, les BIMEVOX, composés dérivés de Bi4V2O11, et les phases dérivées de la Brownmillerite Ba2In2O5. Les deux familles de composés présentent des structures cristallines bi-dimensionnelles. Leurs formes « haute température », conductrices par ions oxyde, sont facilement stabilisées à plus basse température par substitution partielle du vanadium ou de l'indium. La diffraction des neutrons à haute température a permis de déduire des chemins préférentiels pour la diffusion des ions oxyde dans la structure. Les valeurs des barrières énergétiques à la diffusion, déduites des cartes de densité de probabilité de présence des nucléons, ont été comparées aux valeurs des énergies d'activation mesurées par spectroscopie d'impédance. Cependant, les phénomènes de transport de l'oxygène sont plus complexes. Les applications comme électrolyte nécessitent des céramiques denses. Si les BIMEVOX sont faciles à densifier, les phases de type Brownmillerite le sont moins. Par ailleurs, comme le montre l'échange isotopique et les mesures de flux de semi-perméabilité, un autre paramètre doit être pris en compte dans le transport de l'oxygène, le transfert en surface de l'oxygène moléculaire

Unusual concentration of Early Albian arthropod-bearing amber in the Basque-Cantabrian Basin (El Soplao, Cantabria, Northern Spain) : palaeoenvironmental and palaeobiological implications

The El Soplao site is a recently-discovered Early Albian locality of the Basque-Cantabrian Basin (northern Spain) that has yielded a number of amber pieces with abundant bioinclusions. The amber-bearing deposit occurs in a non-marine to transitional marine siliciclastic unit (Las Peñosas Formation) that is interleaved within a regressive-transgressive, carbonate-dominated Lower Aptian-Upper Albian marine sequence. The Las Peñosas Formation corresponds to the regressive stage of this sequence and in its turn it splits into two smaller regressive-transgressive cycles. The coal and amber-bearing deposits occur in deltaic-estuarine environments developed during the maximum regressive episodes of these smaller regressive-transgressive cycles. The El Soplao amber shows Fourier Transform Infrared Spectroscopy spectra similar to other Spanish Cretaceous ambers and it is characterized by the profusion of sub-aerial, stalactite-like flows. Well-preserved plant cuticles assigned to the conifer genera Frenelopsis and Mirovia are abundant in the beds associated with amber. Leaves of the ginkgoalean genera Nehvizdya and Pseudotorellia also occur occasionally. Bioinclusions mainly consist of fossil insects of the orders Blattaria, Hemiptera, Thysanoptera, Raphidioptera, Neuroptera, Coleoptera, Hymenoptera and Diptera, although some spiders and spider webs have been observed as well. Some insects belong to groups scarce in the fossil record, such as a new morphotype of the wasp Archaeromma (of the family Mymarommatidae) and the biting midge Lebanoculicoides (of the monogeneric subfamily Lebanoculicoidinae). This new amber locality constitutes a very significant finding that will contribute to improving the knowledge and comprehension of the Albian non-marine paleoarthropod fauna

Unusual concentration of Early Albian arthropod-bearing amber in the Basque-Cantabrian Basi (El Soplao, Cantabria, Northern Spain): Palaeoenvironmental and palaeobiological implications

The El Soplao site is a recently-discovered Early Albian locality of the Basque-Cantabrian Basin (northern Spain) that has yielded a number of amber pieces with abundant bioinclusions. The amber-bearing deposit occurs in a non-marine to transitional marine siliciclastic unit (Las Peñosas Formation) that is interleaved within a regressive-transgressive, carbonate-dominated Lower Aptian-Upper Albian marine sequence. The Las Peñosas Formation corresponds to the regressive stage of this sequence and in its turn it splits into two smaller regressive-transgressive cycles. The coal and amber-bearing deposits occur in deltaic-estuarine environments developed during the maximum regressive episodes of these smaller regressive-transgressive cycles. The El Soplao amber shows Fourier Transform Infrared Spectroscopy spectra similar to other Spanish Cretaceous ambers and it is characterized by the profusion of sub-aerial, stalactite-like flows. Well-preserved plant cuticles assigned to the conifer genera Frenelopsis and Mirovia are abundant in the beds associated with amber. Leaves of the ginkgoalean genera Nehvizdya and Pseudotorellia also occur occasionally. Bioinclusions mainly consist of fossil insects of the orders Blattaria, Hemiptera, Thysanoptera, Raphidioptera, Neuroptera, Coleoptera, Hymenoptera and Diptera, although some spiders and spider webs have been observed as well. Some insects belong to groups scarce in the fossil record, such as a new morphotype of the wasp Archaeromma (of the family Mymarommatidae) and the biting midge Lebanoculicoides (of the monogeneric subfamily Lebanoculicoidinae). This new amber locality constitutes a very significant finding that will contribute to improving the knowledge and comprehension of the Albian non-marine paleoarthropod fauna

Economic Valuation of Mining Heritage from a Recreational Approach: Application to the Case of El Soplao Cave in Spain (Geosite UR004)

Heritage tourism can increase incomes and stimulate the economy in former mining areas. Recreational tourism is one of the main sources of value of heritage. People from urban areas are willing to pay for access to these tourism options. The measurement of the economic impact of this availability is one of the main problems to confront, due to the immeasurable possibilities of heritage resources. The use of non-market values and their estimation by means of revealed preference methods should help to assess the economic value of this sort of resources from a recreational perspective. The travel cost method (TCM) is widely used to value areas with recreational uses, such as lakes, beaches or forests, but there are not references to previous applications of this methodology in the field of mining heritage. In this work, TCM has been applied to obtain the economic value of El Soplao Cave (Geosite UR004, Cantabria, Spain) as a recreational site, providing an estimated result of 34,961,162 euros

The biota of the Upper Cretaceous site of Lo Hueco (Cuenca, Spain)

The Late Cretaceous (Campanian-Maastrichtian) fossil site of Lo Hueco was recently discovered close to the village of Fuentes (Cuenca, Spain) during the cutting of a little hill for installation of the railway of the Madrid-Levante high-speed train. To date, it has yielded a rich collection of well-preserved Cretaceous macrofossils, including plants, invertebrates, and vertebrates. The recovered fossil assemblage is mainly composed of plants, molluscs (bivalves and gastropods), actinopterygians and teleosteans fishes, amphibians, panpleurodiran (bothremydids) and pancryptodiran turtles, squamate lizards, eusuchian crocodyliforms, rhabdodontid ornithopods, theropods (mainly dromaeosaurids), and titanosaur sauropods. This assemblage was deposited in a near-coast continental muddy floodplain crossed by distributary sandy channels, exposed intermittently to brackish or marine and freshwater flooding as well as to partial or total desiccation events.The Konzentrat-Lagerstatt of Lo Hueco constitutes a singular accumulation of fossils representing individuals of some particular lineages of continental tetrapods, especially titanosaurs, eusuchians and bothremydid turtles. In the case of the titanosaurs, the site has yielded multiple partial skeletons in anatomical connection or with a low dispersion of their skeletal elements. A combination of new taxa, new records of taxa previously known in the Iberian Peninsula, and relatively common taxa in the European record compose the Lo Hueco biota. The particular conditions of the fossil site of Lo Hueco and the preliminary results indicate that the analysis of the geological context, the floral and faunal content, and the taphonomical features of the site provide elements that will be especially useful for reassess the evolutionary history of some lineages of European Late Cretaceous reptiles.Peer reviewe

Plant-dominated assemblage and invertebrates from the lower Cenomanian of Jaunay-Clan, western France

International audienceTwo fossil localities are reported on the "LGV SEA" railroad from the Lower Cenomanianof Jaunay-Clan (JC), near Poitiers, western France. The laminated mudstones yielded plantfossils including ferns (Cladophlebis, Osmundophyllum, Ruffordia goeppertii, Sphenopteris),conifers (Brachyphyllum, Dammarophyllum, Pagiophyllum), and terrestrial and aquaticfreshwater angiosperms (Eucalyptolaurus depreii, Ploufolia). They are associated with acoleopteran insect that shows systematic affinities to the modern subfamily Chrysomeli-nae (Chrysomelidae). This assemblage suggests connections with arborescent vegetationgrowing in calm freshwater environment. Brackish to marine invertebrates also occurand include a dakoticancroid crab (Brachyura, Podotremata, Dakoticancroidea) and a fewbivalves (Brachidontes). They suggest brackish episodes during pond sedimentation in acoastal environment. Lastly, vertebrates are represented by an isolated feather

Adaptations xéromorphes chez des Gymnospermes du Mésozoïque. Une revue avec des implications paléoclimatiques

La cuticule des plantes s’est révélée être un proxy à haute résolution des paléo-variations de la pCO2. Toutefois, la gamme des adaptations xéromorphes est plus large chez les Gymnospermes mésozoïques que chez leurs représentants actuels et ceci pourrait expliquer les différences de DS et IS entre les différents taxa d’un même assemblage fossile. Quatre principales réponses adaptatives aux pertes hydriques sont connues : réduction du rayonnement solaire, des circulations d’air asséchantes, de l’évapotranspiration et piégeage de l’eau de surface. Nous suggérons de compléter les mesures de la densité et de l’indice stomatique par des observations qualitatives des adaptations des microstructures cuticulaires.Plant cuticles have proved to be a high-resolution proxy of palaeo- pCO2 variation. Mesozoic gymnosperms, however, show a wider range of xeromorphic adaptations than their living relatives, and these may explain stomatal density/stomatal index differences between taxa within the same fossil assemblage. Four main adaptive responses to water loss are pointed out: reduction of solar radiation, reduction of drought-air circulation, reduction of evapotranspiration, and trapping of surface external water. In conclusion, we recommend supplementing quantitative estimates of stomatal density and index by qualitative observations of cuticular adaptive macro- and microstructures.</p