Les voiles microbiens. Leur contribution à la fossilisation des organismes au corps mou

Dans certains gisements fossilifères, la conservation des organismes au corps mou est imputable à la prolifération de voiles microbiens. II en est ainsi des shales du Grès à Voltzia (Trias inférieur) où des méduses, des annèlides et diverses pontes sont fossilisés dans des lamines grises, d'épaisseur inframillimétrique, dont la nature bactérienne est démontrée. En recouvrant rapidement les cadavres, les voiles microbiens les protégeaient contre les animaux saprophages et les actions mécaniques. En měme temps, ils créaient un milieu clos, appauvri en oxygène, qui inhibait la décomposition de la matière organique. □ Fossilisation, voiles microbiens, cyanobactéries, Buntsandstein.
Preservation of soft-bodied organisms in some fossiliferous localities is attributable to spreading of microbial veils. This is the case of the shales of the Grès à Voltzia (Lower Triassic), where fossil medusae, worms and clutches occur in grey, less than a millimeter thick laminae, the bacterial origin of which is demonstrated. Covering the bodies rapidly, the microbial veils protected them from scavengers and physical injuries. They created enclosed spaces, with poor oxygen content, inhibiting the decay of organic matter. □ Fossilization, microbial veils, cyanobacteria, Buntsandstein.     

Les vagues de peuplements humains au Pléistocène inférieur et moyen dans le bassin de la Loire moyenne, région Centre, France. Apports de l’étude des formations fluviatiles

Evidence of earliest human settlements had been searched in the alluvial formations laid down in the Middle Loire Basin. Many stepped sheets deposited during the successive interglacial-glacial quaternary cycles are studied in four valleys of the Loire tributaries: the Creuse, Indre, Cher and Loir rivers. These sandy remnants are systematically dated, using the Electron Spin Resonance method applied on bleached fluvial quartz. Five settlements which contain very Early Palaeolithic industries with Mode 1 technology were occupied during the Lower Pleistocene. About eighty sites with hand-axe assemblages are observed in Middle Pleistocene remnants; nine of these are described in this paper. The results theorize that the geographical center of France (47°N) would be reached by two influxes of human populations with an interval around 400 years, because major climatic pejorations, particularly at the end of the Lower Pleistocene. These two populations produced lithic industries with many differences in supply of raw materials and in techniques of striking. Not any typologic link had been observed joining the two industrial unities.     

Diaceratherium massiliae nov. sp. des argiles oligocènes de Saint-André et Saint-Henri à Marseille et de Les Milles près d’Aix-en-Provence (SE de la France), premier grand Rhinocerotidae brachypode européen

A revision of all previously collected mammalian fossils from the two Late Oligocene sites of Saint-André and Saint-Henri in Marseille (both from the MP 26 reference-level) allows us to identify three Rhinocerotoidea species: Protaceratherium albigense, Ronzotherium romani, Diaceratherium massiliae nov. sp., and maybe a fourth one, Eggysodon cf. gaudryi. Only the first two were previously known there. D. massiliae nov. sp. is found together with R. romani; it is the first case of sympatry ever known between the two genera. D. massiliae nov. sp. is then the most ancient Diaceratherium in Europe, where the genus was previously unknown before the MP 29 reference-level. It is a very large species whose limb bones proportions foreshadow these of the later species of the genus, especially D. lemanense from the Late Oligocene-Early Miocene. This suggests a possible phylogenetic link between D. massiliae nov. sp. and D. lemanense, and the coexistence of at least two different but partially contemporaneous lineages among the European Diaceratherium. In Les Milles near Aix-en-Provence, also from the MP 26 reference-level, the three species P. albigense, R. romani and D. massiliae nov. sp. were also found.