Yanbu Fm
Type Locality and Naming
Middle unit of the Tayran Gr . Hughes and Filatoff (1995) named the Yanbu Formation for a subsurface succession of evaporites in the Yanbu region of western Saudi Arabia. The Yanbu Formation is defined in the Saudi Aramco exploration well Yanbu-6 (YNBU-6: 24°06′54.0″N, 38°08′59.0″E) between 2,684–3,145 ft (461 ft, 140.5 m thick), onshore coastal Saudi Arabian Red Sea. Column: Red Sea Saudi Arabia (although present only in a small part of it.). Middle formation in Tayran Gr
Synonym:
Lithology and Thickness
Evaporite - halite and/or anhydrite with minor shale.
Relationships and Distribution
Lower contact
Regionally, the schematic strat column indicates the next older unit as Al Wajh Fm. In the subsurface, the Yanbu Fm consists of anhydrite and halite that conformably overlie the Al Wajh Fm siliciclastics and in places are interbedded with them.
Upper contact
Regionally, the adjusted schematic strat column for graphic purposes would assign the next younger unit as Musayr Fm. However, these are largely coeval. "In a normal sequence, the Yanbu Fm is interpreted to be unconformably overlain by the Burqan Fm, based on the dramatic paleoenvironmental contrast between the shallow, restricted Tayran Gr and the deep-marine Burqan Fm sediments. Exposures in the Midyan region also provide evidence for this unconformity." (Hughes and Johnson, 2005)
Regional extent
Localized distribution. The Yanbu Formation is not exposed in the Saudi Arabian Red Sea region. The Yanbu Formation is not exposed along the Red Sea coast, but halite and anhydrite have been penetrated in exploration wells in the Yanbu Basin and to the north in Midyan (Cocker and Hughes, 1993).
The Yanbu Fm is correlated to the Ghara Member of the Nukhul Fm (Saoudi and Khalil, 1984) in the Gulf of Suez and Egyptian Red Sea; and in the subsurface in the Yemeni and Somali Gulf of Aden (Hughes and Beydoun, 1992). (Hughes and Johnson, 2005)
GeoJSON
Fossils
Palynoflora from the intra-evaporitic sediments include the halophytic pollen Retiperiporites spp. but lack marine indicators; no microfauna are present.
Age
Depositional setting
Its localized distribution and often cryptic layering represent precipitation in hypersaline water. The deposition of the Yanbu Formation is probably due to an early restricted marine incursion related to the earliest stage of the opening of the Red Sea. Orszag-Sperber et al. (1992) suggest that the deposition of the evaporites was related to the beginning of the Red Sea rift and to the tectonic control of restricted marine conditions rather than to a fall in sea-level. The purity of the evaporites argues against a sabkha origin and they probably formed in localized hypersaline ponds in a salina setting, although sabkha evaporites may exist locally." (Hughes and Johnson, 2005)
Additional Information