The nature of the Permian-Triassic boundary on the Saharan Platform area is geographically variable. In the northeastern region of the Saharan Platform (southern extremity of Tunisia and northern Tripolitania) the Permian, which is locally conformable upon the Carboniferous, and is itself overlain conformably by the Trias, is partially marine (the only marine Permian to be found on the African continent). Overlying the thick Lower Permian sequence with marine fossils, and a less fossiliferous Middle Permian that is mainly dated by its stratigraphic position, lies the richly-fossiliferous Upper Permian. This Upper Permian is extremely thick locally (about 6,000m or 19,680 at Tebaga de Medenine), thinning with increasing proportions of clastic material to the west, south and south-east. Before wedging out completely it discordantly trangresses various Paleozoic horizons. It is the precursor of the on-lapping transgressions that begin with a major transgression in the Trias and continue intermittently during most of the Mesozoic.

Although the Trias is sometimes conformable upon the Permian, it is found that to the west, south and south-east (Algeria, Tunisia and Libya) the Trias extends far beyond the Permian limits and transgresses older Paleozoic beds. The Lower Triassic, dated mainly by its stratigraphic position, and the richly fossiliferous Middle Trias together make up a clastic formation called the "Trias greseuz". Toward the center and north-east of the basin part of this formation changes laterally to evaporites which continue to occur in the Upper Trias.

On the rest of the Saharan Platform, some of the continental beds are questionably identified as Permian. These are found in restricted, isolated, residual basins forming part of the Paleozoic cycle. (Tigentourine Series in the Polignac Basin; Abadla; Tindouf?). The absence of an overlying conformable Lower Triassic cover for these beds suggests that the Lower Trias was never deposited here.

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