First description of Skolithos burrows from the Cambrian–Ordovician boundary interval of the Central Anti-Atlas, Morocco

Skolithos burrows indicate high-energy nearshore environment. In this paper, abundant Scolithos burrows from two particular levels of the Cambrian–Ordovician boundary interval of the Central Anti-Atlas, Morocco, are described for the first time. The first level occurs at the boundary between the Azlag Formation and Jbel Lmgaysmat Formation (Furongian), where the burrows are 5–80 cm long and 3–7 mm wide, straight to slightly curved, with mostly circular, but sometimes also oval apertures. The second level occurs within the unconformity underlining the Tremadocian cycle (Fezouata Shale). The burrows of Skolithos linearis associated with that level are straight to slightly curved, 2–15 cm long and 2–4 mm wide. The absence of encrustation above the burrowed beds indicates that these traces were made in a soft sediment.