Figure_16. Paleogeographic maps of the Western High Atlas (Morocco) during the Neogene (Oligocene to Lower Pliocene)

The Oligo-Miocene, which includes the Chattien and Aquitanian stages (27.82-20.44 Ma), saw a partial retreat of the sea, creating lagoon-marine basins along the Agadir coast, protected by the Western High Atlas (HAA) chain to the north and Cretaceous formations to the south. These basins have received deposits of rolled pebbles from the erosion of the Paleozoic mountains and the Argana corridor. These pebbles, transported over long distances by fluvial processes, underwent littoral dynamics and formed conglomerates with bleached surfaces. Towards the southeast of the HAA, the pebbles are more rolled and bleached, while towards the northwest these facies are rare or absent. The first traces of compressional tectonics are observed, marked by a clear angular unconformity at the Maastrichtian-Oligocene-Miocene boundary. During the Pliocene, two units (U1 and U2) show an initial transgression followed by regression, with marine deposits rich in warm water fossils. The association of microfauna such as Ammonia beccarii and planktonic foraminifera has allowed the dating of these strata, testifying to the increasing marine influence of the Lower Pliocene.