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The Gordon Lake Formation (GLF) of the Paleoproterozoic Huronian Supergroup is a siliciclastic-dominated succession ranging from 300 to 1100 m in thickness. Lithostratigraphic and sedimentological analyses of the formation in the Bruce Mines and Flack Lake areas, and Killarney and Lady Evelyn-Smoothwater provincial parks, Ontario, Canada, revealed seven lithofacies, which comprise three distinct lithofacies associations. The lithofacies associations are subtidal nearshore, subtidal to shallow shelf, and mixed intertidal flat. A variety of structures interpreted to be biogenic in nature, including microbially induced sedimentary structures (MISSs) and stromatolites, are preserved, which support local microbial colonization in a tidally influenced marine environment. Wave, current, and tide-generated sedimentary structures, including symmetrical ripples, trough cross-beds, flaser and lenticular bedding, and mudstone drapes, are abundant in all study areas. Storm influence is suggested by normally graded deposits, mudstone rip-up clasts, and soft-sediment deformation structures (SSDSs), including load casts, ball-and-pillow structures, convolute bedding, and pseudonodules. Interbedding and interlamination of sandstone and mud-stone units are present throughout the GLF and represent fluctuations in water level and energy, related to tidal and storm processes. A lowermost carbonate-rich unit may represent a period of low clastic influx. The contacts with the underlying Lorrain and overlying Bar River formations appear gradational. The depositional environment can be visualized as an open coast, shallow marine shelf that was influenced by microbial mats, tides, and storms. Key words: Huronian Supergroup, Paleoproterozoic, siliciclastic, shallow marine, tides, microbial mats, Introduction Precambrian sedimentary systems are notoriously difficult to interpret due to the absence of pronounced biological activity, especially bioturbation (Schopf 1975; Eriksson et al. 2004 and references therein; Flannery et [...]

ZnO nanostructures of various morphologies and crystallinities were fabricated by thermal evaporation from Zn powder in a tube furnace in the presence of oxygen. It was found that the morphology of ZnO nanostructures was affected by synthesis parameters, such as growth temperature, carrier gas flow, and the presence of catalyst on the surface of the substrate. Representative ZnO nanostructures were studied by X-ray excited optical luminescence (XEOL) and cathodoluminescence (CL) methods. The luminescence from these samples exhibits a morphology dependence of the branching ratio of the near band gap (NBG) emission in the UV and defect emission in the green (GE). The appearance of the optical emission also depends on the excitation method. X-ray absorption near-edge structures (XANES) at the O K-edge and Zn L-edge are also presented and their implications discussed. Key words: ZnO nanostructures, XEOL, XANES, cathodoluminescence. Faisant appel a une methode d'evaporation thermique d'une poudre de Zn dans un four electrique a tube en presence d'oxygene, on a fabrique des nanostructures de ZnO de morphologies et de cristallinites diverses. On a trouve que la morphologie des nanostructures de ZnO est affectee par divers parametres de la synthese, telle la temperature de croissance, la vitesse d'ecoulement du gaz et la presence de catalyseur sur la surface du substrat. On a etudie les structures de nanostructures de ZnO representatives en faisant appel aux methodes de luminescence optique excitee par rayons-X (LOEX) et de cathodoluminescence (CL). La luminescence dans ces echantillons presente, dans l'UV, une relation entre la morphologie sur le rapport de ramification et l'emission de la bande interdite rapprochee (BIR) et l'emission de defaut dans le vert (EV). L'apparition d'une emission optique depend aussi de la methode d'excitation. On a aussi determine les structures d'absorption des rayons-X pres du seuil (' XANES ') au seuil K de l'oxygene et au seuil L du zinc et on discute de leurs implications. Mots-cles : nanostructures du ZnO, luminescence optique excitee par rayons X (LOEX), structures d'absorption des rayons X pres du seuil (<< XANES >>), cathodoluminescence. [Traduit par la Redaction], Introduction Zinc oxide, a versatile technological material for light emitting and photonic applications (e.g., solid-state lasers and LEDs), is a semiconductor with a wide band gap (~3.37 eV) and large [...]