Lower Cretaceous-Upper Jurassic Stratigraphy of Umm Shaif Field, Abu Dhabi Marine Areas, Trucial Coast, Arabia

The Umm Shaif field, located in the Abu Dhabi Marine Areas Concession, offshore of the Sheikdom of Abu Dhabi on the Trucial Coast of Arabia, was recently brought into production. Independent studies of the petrography and paleontology arrived at similar conclusions as to the geological history of the Lower Cretaceous-Upper Jurassic rocks, and these different lines of approach are co-ordinated in this joint paper. In the Umm Shaif area, the rocks assigned to the Upper Jurassic and Lower Cretaceous represent four major and separate sequences of deposition. The basal Cretaceous (Lowest Neocomian) beds are thought to be represented by a basal conglomerate which is transgressive across and lies disconformably on the marine Upper Jurassic (Callovian-Oxfordian). The Neocomian marine sedimentation was interrupted by a period of regression which resulted in the deposition of a dolomite-anhydrite formation at Umm Shaif. The Lower Cretaceous-Jurassic succession in Umm Shaif is compared with that in Qatar. In the light of the recently observed subaerial formation of anhydrite, the stratigraphical and paleogeographical relationships of the anhydritic rocks of the Persian Gulf are discussed and compared with similar successions in nearby areas. The need for similar reconsideration of the rocks of this age in the western Persian Gulf is emphasized.