Archaeocyathid fauna of the lowest fossiliferous levels of Tiout (Lower Cambrian, Southern Morocco)

Abstract

The oldest archaeocyathid fauna from Tiout (Anti-Atlas, Morocco) contains 15 species belonging to 11 genera. The following species: Aldanocyathus cribratus, Neoloculicyathus magnus, Coscinocyathus primus, C. secundus, C. fasciola, Tumulifungia marocana, Gordonifungia cowieiare new. The biostratigraphy of this archaeocyathid fauna demonstrates that the lower boundary of the Amouslekian stage should be moved downwards to within the ‘Calcaires Supérieurs’ of the Adoudounian (Assadassian or equivalent Ouneinian). One or perhaps more archaeocyathid and trilobite zones may yet be found beneath this boundary at Tiout. The uppermost ‘Calcaires Superiéurs’ may be dated, on the basis of Archaeocyatha, as equivalent to the Atdabanian stage, but not to the lowest part of it. The underlying fossiliferous horizons should be equivalent to all or part of the lower Atdabanian. The Precambrian–Cambrian boundary in Morocco can be looked for lower in the succession and defined on the basis of other fossil groups.