Late Early Carboniferous conodonts from a supposed Middle Devonian reef limestone of the Marrakech region (Morocco)

Field and microfacies analyses of supposed Middle Devonian reef limestones at El Moussira (Haouz region south of Marrakech) showed that they represent in fact a shallowing upwards, shallow marine, crinoid-rich, open carbonate ramp that ends with a regionally unique, current/storm ridden, laminated microbial facies. Rare records of Mestognathus bipluti Higgins 1961 from the base and top, in conjunction with comparisons of the adjacent Carboniferous successions of the High Atlas and Jebilet, suggest a late Visean age, correlating with the maximum spread of carbonate deposition in the Western Meseta. There is no evidence for a Middle Devonian reef belt stretching towards the High Atlas or for a Famennian/Tournaisian clastic wedge of the Haouz area. The middle/late Visean onset of the main Variscan orogeny did not prevent the faunal exchange of shallow (Mestognathus) and deeper water (various goniatites) biota across the narrowing 'Variscan Sea' between NW Gondwana and Laurussia. Mestognathus is thought to have had a wider paleoecological range than previously assumed by some authors, stretching from tidal lagoons to strongly turbulent inner shelf and, occasionally, even into calm, subphotic, pelagic cephalopod facies. This increases its correlation potential across facies.