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In the region of In Amenas (south-eastern Algeria) Triassic deposits crop out, on top of Palaeozoic rocks under an angular unconformity. Astudy of their sedimentological and palaeoenvironmental characteristics has revealed asandy-clay unit with vertebrate remains, tree trunks and ichnofossils of Middle-Late Triassic age. This so-called Zarzaitine Formation, which reflects deposition in adeltaic environment, shows three facies associations. The first defines an upper and shallow intertidal mixed flat zone with in-situ temnospondyl capitosauroid remains, associated with Skolithos ichnofacies, while the second one defines alower intertidal delta plain zone, composed of sandstone, distributary channels and muddy interdistributary areas,which record daily tidal rhythmites and monthly tidal bundles. The third, and last, facies association represents an upper delta plain of the supratidal zone, characterised by coarse sandstone deposits of braided rivers and aCycadophyta palaeosol. Previous work, which led to considering these Triassic deposits as aseries composed of four formations, deposited in abraided rivers environment, whose lower floodplains constituted ecological niche for atemnospondyl fauna, under hot and dry climatic conditions and plants belonging to this same formation, for mushrooms and algae, will also be considered.

Spinel oxides are a type of material that can be used in a wide range of applications, such as photocatalysis, hydrogen production and environmental protection. In this respect, calcium aluminate (CaAl2O4) and chromate (CaCr2O4) spinels were synthesized in this study by the coprecipitation method using potash solution as a precipitant. CaAl2O4 and CaCr2O4 spinels were annealed at 900 and 1100°C, respectively, for different periods. The obtained spinels were first characterized by thermal analysis, and the phase composition of the oxides was analysed using X-ray diffraction. Hydroxyl groups and absorbed water in the obtained precipitates disappeared after calcination and were observed via Fourier transform infrared spectroscopy. BET and SEM/EDS analyses were also used to determine the total surface area of the powder particles, the size of the grains and the morphology of the powders of the synthesized nanoparticles, respectively. The structural and morphological analyses revealed the formation of single-phase CaAl2O4 and dual-phase CaCr2O4, with specific surfaces for each spinel of 44.2165 and 5.7190 m2 g−1, respectively. Moreover, DFT calculations were performed on the materials, and the direct bandgaps of these spinels were found to be 4.365 eV for CaAl2O4 and 2.256 eV for CaCr2O4. The results indicated that different compositions led to different optical bandgaps. Finally, the results indicate that due to the suitable characteristics and properties of the produced spinel oxides, they are among the promising materials that may be employed as semiconductors for various applications. [ABSTRACT FROM AUTHOR]