The sandstones, shales, and thin beds of argillaceous limestone previously included as the basal part of the Permian Khuff Formation were described as the Unayzah Formation by al-Laboun in 1982 and 1986. The type locality (stratotype?) of this formation is in the town of Unayzah, and a reference section was established in the Qusayba area, al-Qasim district, Saudi Arabia. Fossil flora collected from outcrops and palynomorphs obtained from boreholes support a Late Carboniferous-Early Permian age for these strata. The Unayzah Formation is conformably overlain by the massive carbonates of the Khuff Formation, whereas its basal contact is marked by a regional angular unconformity with various older units. The Unayzah Formation is widespread in the Greater Arabian basin. The f rmation represents cyclic transgressive and regressive deposits preceding the Permian regional marine transgression, during which the massive carbonates of the Khuff Formation were deposited. This Permian transgression marked a major change in the sedimentation and evolution of the Greater Arabian basin.

The porous sandstones of the Unayzah Formation are important exploration targets because several fields in the eastern and southeastern parts of the Greater Arabian basin produce hydrocarbons from the Unayzah.