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Unconformities represent breaks in the depositional record and important correlation surfaces. It is not uncommon for more time to be represented by such surfaces than the time it took to deposit the strata bounded by unconformites. Strata bounded by unconformities delineate depositional sequences whose internal facies are genetically related to one another. An understanding of such stratigraphic relationships helps in the prediction of lateral facies relationships. Because of their iportance, it is imparative to recognize the characteristics of unconformities in the stratigraphic record. The section below provides a few examples of major unconformities.

Outcrop photograph (F.O. Meyer, 1999) showing the unconformity between the Hanifa and overlying Jubaila Formations. Note iron stained carbonates that make up the upper beds of the Hanifa Formation, Wadi Birk, Saudi Arabia.

Detailed view of Hanifa-Jubaila unconformity shows transgressive lag deposit made up of rounded carbonate boulders pave the unconformable surface. Oysters encrust surface on right side, (F.O. Meyer, 1999), Wadi Birk, Saudi Arabia.

Outcrop Photograph (F.O. Meyer, 2000) showing the uncoformity between the Midnab and Kartum Members of the Khuff Formation, Saudi Arabia. Note well preserved Cliche profile and iorn stained top of Midnab member.

Outcrop Photograph (F.O. Meyer, 2000) showing the growth of stromatolite (blue-green algae) heads on the pre Kartum uncoformity. These . Red shale encloses the lower two heads located just above the unconformity.