Lithostratigraphy of the Red Sea Region

Abstract

ABSTRACT The onshore and offshore Saudi Arabian Red Sea region contains a series of lithostratigraphic units that have not previously been formally defined and described. Based on an intensive study of the succession, a lithostratigraphic scheme is proposed in a lexicon format that integrates biostratigraphic, sedimentological, seismic and field studies from the Midyan Peninsula in the north, to the Jizan Coastal Plain in the south. In view of the economic aspect of the Neogene succession and greater accessibility to Neogene subsurface samples, emphasis has been placed on a revision of the Neogene lithostratigraphy. Resting upon Proterozoic Basement, the sedimentary succession was deposited during the Cretaceous to Pleistocene times. The oldest pre-rift Suqah Group nonconformably overlies the Proterozoic Basement and consists of Upper Cretaceous shales of the Adaffa Formation and Cretaceous to Palaeogene sandstones, shales and thin limestones of the Usfan Formation. A series of volcanics includes the early to middle Oligocene Matiyah Formation and the late Oligocene-early Miocene Jizan Group. The Neogene succession displays a great lithological diversity. The Tayran Group (Al Wajh, Musayr and Yanbu Formations) includes marginal marine siliciclastics of the Al Wajh Formation, and represents the earliest rift-associated sediments deposited during the earliest Miocene. These are conformably overlain by lower Miocene shallow-marine carbonates of the Musayr Formation. In some of the central Red Sea onshore basins, thick lower Miocene submarine evaporites of the Yanbu Formation were deposited under locally restricted conditions and form the third formation of the Tayran Group. Rapid subsidence during the early Miocene caused deposition of deep-marine, planktonic-foraminiferal mudstones and thick submarine fan sandstones of the Burqan Formation. Carbonates, marine mudstones and submarine evaporites of the Maqna Group (Jabal Kibrit and Kial Formations) unconformably overlie the Burqan Formation and were deposited during latest early Miocene to earliest middle Miocene. The Jabal Kibrit Formation consists of an anhydrite-carbonate facies, of which the carbonates form the Wadi Waqb Member. Siliciclastic facies of the Jabal Kibrit Formation are termed the Umm Luj Member. Above the Jabal Kibrit Formation, the Kial Formation is typified by interbedded anhydrites, calcareous siltstones and carbonates, and includes the Sidr, Nakhlah, Yuba, Rayaman and Sabya Members. Within the region, thick evaporites of the Mansiyah Formation were deposited extensively during the middle Miocene, and are overlain by poorly exposed sands, shales and thin anhydrite beds of the middle to upper Miocene Ghawwas Formation. The Lisan Group unconformably overlies the Ghawwas Formation and consists of coarse alluvial sands and gravels of possible Pliocene to Holocene age.