Shallow to marginal marine ichnoassemblages from the Upper Pliocene Slama Formation (Lower Chelif Basin, NW Algeria)

The Slama Formation (Upper Pliocene, Lower Chelif Basin, Algeria) displays siliciclastic deposits distributed in five determined stratigraphic members: Lower Sandstone Member, Lower Marls Member, Middle Sandstone Member, Upper Marls Member, and Upper Sandstone Member. It is characterised by low to moderate ichnofossil diversity consisting of 16 ichnotaxa: Arenicolites isp., Conichnus conicus, Gyrolithes polonicus, G. variabilis, Gyrolithes isp., Macanopsis isp., Macaronichnus segregatis, Ophiomorpha cf. annulata, O. irregulaire, O. nodosa, Palaeophycus isp., Skolithos linearis, Skolithos isp., Thalassinoides horizontalis, T. paradoxicus, and T. suevicus. Trace fossils are grouped into four ichnoassemblages. The Thalassinoides ichnoassemblage (Lower Sandstone Member and Lower Marls Member) represents a mixed Cruziana/Skolithos ichnofacies. The Skolithos ichnoassemblage (Middle Sandstone Member) represents the archetypical Skolithos ichnofacies and corresponds to middle shoreface settings. The Macaronichnus– Gyrolithes ichnoassemblage (Upper Marls Member) indicates shoreface/foreshore contact. The Ophiomorpha ichnoassemblage (Lower Sandstone Member) can be interpreted as the proximal Skolithos ichnofacies, which possibly corresponds to foreshore settings. The suggested dominant, regressive phase corresponds to the second half of the Upper Pliocene eustatic cycle in the northern Tell Atlas foreland domain.