The Oulad Abdoun Basin (also known as the Ouled Abdoun Basin or Khouribga Basin) is a phosphate sedimentary basin located in Morocco, near the city of Khouribga. It is the largest in Morocco, comprising 44% of Morocco's phosphate reserves, and at least 26.8 billion tons of phosphate. It is also known as an important site for vertebrate fossils, with deposits ranging from the Late Cretaceous (Maastrichtian) to the Eocene epoch (Ypresian), a period of about 25 million years.
The Oulad Abdoun is located west of the Atlas Mountains, near the city of Khouribga. The Oulad Abdoun phosphate deposits encompass some , an area of . The Oulad Abdoun is the largest and northernmost of Morocco's major phosphate basins, which from northeast to southwest, include the Ganntour, Meskala, and Oued Eddahab (Laayoune-Baa) basins.
The Oulad Abdoun Basin stretches from the late Cretaceous to the Eocene and contains abundant marine vertebrate fossils, including sharks, bony fish, turtles, crocodilians, and other reptiles, as well as sea birds and a small number of terrestrial mammals.
Bird fossils are common in the Basin, which includes the oldest birds in Africa. At least three orders and several families of sea birds are represented, including Procellariiformes (albatrosses and petrels, fossils assignable to Diomedeidae and Procellariidae), Pelecaniformes (pelicans and allies, fossils assignable to Phaethontidae, Prophaethontidae, Fregatidae and Pelagornithidae), and Anseriformes (waterfowl, including fossil Presbyornithidae).
The late Maastrichtian deposits of the Khouribga Phosphates preserve abundant mosasaur fossils, especially isolated teeth. At least fifteen species are represented, covering the majority of ecological niches the group is known to have occupied. The Ouled Abdoun Basin is one of the richest known mosasaur fossil sites in the world.
Plesiosaur material found in the Ouled Abdoun Basin has been referred to one valid species, Zarafasaura oceanis. Isolated elasmosaurid fossils may all belong to this species but comparison is difficult.