Three regional unconformities are recognized during stratigraphic studies of Cretaceous sedimentary rocks of the Arabian Peninsula. The Cretaceous sequence can be divided into early (Neocomian through early Aptian), middle (late Aptian through early Turonian), and late (Coniacian through Maestrichtian) units by three unconformities of major importance: (1) an unconformity that represents erosion or nondeposition of the middle Aptian section and marks a significant lithological change from shallow shelf limestones of the Shuaiba Formation to overlying shallow shelf clastics of the Nahr Umr Formation; (2) an unconformity that reflects erosion or nondeposition of Turonian strata and is a break between shallow shelf limestones of the Mishrif Formation and overlying de p-water beds of the Fiqa Formation; and (3) an unconformity that separates the Cretaceous and Tertiary formations capping shallow shelf limestones of the Simsima Formation. A regional unconformity at the Jurassic-Cretaceous boundary has not been recognized.

The subaerial exposure and erosion represented by each of the three unconformities is of great economic importance due to the development of reservoir-quality secondary porosities in rudist reef-bearing limestones. When the ages of these unconformities and the intervening depositional cycles in the Arabian Peninsula are compared with published eustatic curves, several differences are evident.