Fig. 4

Field photos of the studied outcrop, the microfacies and the macrofossil content (Jbel Asdaf area). A Microfacies of upper Tournaisian sandstones in the Aït Yalla Formation, showing fine facies with well-rounded elements, dominated by quartz. B Some macrofaunal fossils from the lower and upper intervals. 1–2. Zaphrentoides sp., 3. Caninophyllum skourense, 4. Gigantoproductus giganteus. C Bioturbation and traces fossils (burrows) in the lower interval. D Microfacies of lower Visean (middle interval) with organic material. E Trace fossils of the ichnogenus Zoophycos (middle/upper interval). F Laminated structures and algal mats (upper interval)