Abstract Fossiliferous marine Pliocene deposits outcropping over a large area on the southern flank of the Belelieta hills, in the region south of the Edough massif and bordering the Bone plain, Algeria, are characterized by a coarsely conglomeratic facies. The material forming the deposits was derived from crystalline basement rocks. Together with Pliocene deposits of the Cap-de- Fer region they apparently represent an island in Pliocene time. Violent tidal currents in the narrow channel separating the island from the mainland probably explain slightly aberrant details of sedimentation.