Programme des sessions > Recherche par auteur correspondant > Elbakhouch Nouhaila

Clastic sediments from the Ediacaran and Cambrian periods within the Tighardine Formation of the Western High Atlas have been investigated to determine their provenance, tectonic setting, and paleo-oxygenation conditions. Geochemical data indicate that the Cambrian clastic sediments are predominantly shales, while the Ediacaran deposits consist mainly of shales with minor wackes. The Cambrian shales (Ca-S) exhibit a relatively uniform composition, with SiO₂ contents ranging from 52.35 to 60.60 wt.%, Al₂O₃ from 18.37 to 24.81 wt.%, Fe₂O₃ from 5.65 to 9.93 wt.%, and TiO₂ from 0.8 to 1.07 wt.%. In contrast, the Ediacaran shales (Ed-S) show greater geochemical variability, with SiO₂ ranging from 33.52 to 77.90 wt.%, Al₂O₃ from 11.12 to 26.12 wt.%, Fe₂O₃ from 0.74 to 13.34 wt.%, and TiO₂ from 0.58 to 5.10 wt.%.

The higher Al₂O₃ concentrations in the Cambrian shales are associated with increased mica content, corroborated by petrographic analyses. Variations in Al₂O₃/TiO₂ and TiO₂/Zr ratios point to a felsic source for the Cambrian shales, while the Ediacaran shales are interpreted to have originated from an intermediate source with contributions from both mafic and felsic lithologies. Both shale groups yield Th/Sc ratios greater than 1, indicating a continental, silicic provenance. Tectonic discrimination diagrams place the Cambrian shales between active and passive continental margin fields, whereas the Ediacaran shales plot within the active continental margin field. These results are consistent with the regional tectonic setting and associated volcanic activity. Redox-sensitive proxies, such as V/Cr ratios, indicate that the Cambrian shales were deposited under oxic conditions, whereas the Ediacaran shales formed in an anoxic environment, as evidenced by the presence of a graphitized zone within the Ediacaran strata of the study area.