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In the Ennedi Plateau, northeastern Chad, Cambrian(?)-Ordovician to Carboniferous strata represent one of the most proximal succession of the north-facing Gondwana platform. This study presents preliminary results related to the c. 200 m-thick Lower Sandstones and overlying Bedo Formation, which essentially record Early to Middle Ordovician flooding events and the end-Ordovician glaciation and subsequent deglaciation. In the Lower Sandstones, fluvial-dominated deposits (prevailing cross-stratification, NW to NNE paleocurrent trends) include intervening high-frequency marine incursions (tidal deposits, ichnofacies including Cruziana and Arthrophycus). Above an erosional unconformity, the end-Ordovician glacial record consists of fluvioglacial conglomeratic deposits atop the Lower Sandstones, which are in turn superimposed by the fine-grained Bedo Formation. The latter interval, onlapping an exhumed erosion surface showing north-trending km-scale glacial lineations, shows glaciomarine deposits only at its base and possibly include Lower Silurian deposits in its upper part. [ABSTRACT FROM AUTHOR]

Cet article questionne les visions de la participation telles qu’elles se donnent à voir lorsque des collectivités territoriales font appel à des plateformes numériques en tant qu’outils d’aide à la décision. Le dispositif Carticipe étudié dans cet article, est une plate-forme cartographique sur laquelle les citoyens sont invités à déposer leurs propositions dans le cadre de concertations urbaines. Au-delà des promesses, l’usage d’un outil numérique permet-il d’encourager la participation citoyenne en la rendant plus accessible et ludique ? L’analyse proposée ici examine les concepts de participation, consultation, concertation et montre combien les spécificités techno-sémiotiques de la plate-forme jouent un rôle majeur dans la probabilité d’aboutissement d’un projet urbain.

Abstract: Enigmatic calcareous microfossils are present in the stratotype section at Tercis, Landes, France (Campanian–Maastrichtian boundary). Thirty to thirty-five forms have been pictured and 1 to 100 specimens have been picked for each of them. The single-chambered tests show a small aperture. They present an axial symmetry, which is altered when radial equatorial expansions are added to the 75 to 200μm-large bodies of discoidal, spheroidal, cupuliform, conical or barrel-like shapes. These peculiar characters are those of the gilianelles, a group of uncertain status created here. In addition to their palaeontological interest, these microfossils display a short time distribution and might have a stratigraphical interest. Gilianella stellata n. gn. n. sp. is described as a type form and illustrated. [Copyright &y& Elsevier]

Calcite samples were extracted both from the rock matrix and the superficial coating of a karstified fault plane of an underground quarry, located in the eastern border of the Paris basin. The karstification is dated as Quaternary. Analysis of mechanical calcite twinning reveals that only the calcite matrix has also undergone a compression trending WNW that can be attributed to the Mio-Pliocene alpine collision. Both coating and matrix have undergone a strike-slip regime with σ1 roughly trending north–south, that could correspond to the regional present-day state of stress, a strike-slip compression rather trending NNW, modified by local phenomena. To cite this article: M. Rocher et al., C. R. Geoscience 335 (2003). [Copyright &y& Elsevier]