Jabal Kibrit Fm

Hughes and Filatoff (1995) first published the name Jabal Kibrit Formation (after Jabal Kibrit) following in-house usage by Saudi Aramco since 1992. The type area for Jabal Kibrit Formation is Jabal Kibrit in the central Midyan region. Column: Red Sea Saudi Arabia. Reference Section and Thickness: The Jabal Kibrit Formation is represented in Saudi Aramco exploration well Midyan S-1 (MDYN-1: 28°10′34.4″N, 34°52′12.9″E) between 6,876–7,447 ft (571 ft, 174.1 m thick), onshore coastal Saudi Arabian Red Sea. Lowermost formation in Maqna Gr

Synonym: the carbonates of the Khuraybah Fm and the siliciclastics of the Usayliyah Fm, as defined by Clark (1986) in the Aynunah area, are assigned to the Jabal Kibrit Fm. Clark’s Usayliyah Fm is exposed to the west of the main outcrop of the Adaffa Fm (28°07′43″N, 35°12′01″E) and overlies the Khuraybah Fm.

Sandy limestone. In the Reference Section, the Jabal Kibrit Fm consists of calcarenites, marl, sandstones, siltstones, and shales. The calcarenites and marls in these sections could be a distal equivalent of the Wadi Waqb Member. "The Jabal Kibrit Formation is represented in outcrop within the Midyan region only by the carbonate Wadi Waqb Member, but elsewhere it is sometimes replaced by the siliciclastic Umm Luj Member (R.S. Johnson, D. Rodgers and G.R. Savage, 1995, Saudi Aramco Report). An anhydrite unit is here [Hughes and Johnson, 2005] termed the An Numan Member, while the uppermost clastic unit is called the Dhaylan Member.

The Umm Luj Member lithology is coarse-and fine-grained arkosic sandstones and laterally equivalent non-calcareous siltstones and mudstones. It has a sporadic distribution and variably replaces the Wadi Waqb Member as a lateral facies equivalent. It is named (Hughes and Johnson, 2005) after the Saudi Aramco exploration well Umm Luj-1, and defined in Saudi Aramco exploration well Al Wajh South-1 (AWSO-1) between 6,336–9,443 ft, onshore coastal Saudi Arabian Red Sea; It is present only in the subsurface of the Al Wajh Basin, and is conformably overlain by the Rayaman Member of the Kial Fm. The depositional environment is deep marine, based on the regional association with deep-marine, outer-shelf to upper-bathyal benthonic and planktonic-bearing sediments.

The Dhaylan Member is calcareous mudstones and siltstones with subordinate very fine- to fine-grained calcite cemented quartz sandstones. It is named and defined in the Saudi Aramco exploration well Dhaylan-1 (DYLN-1: 25°30′37.2″N, 37°02′54.6″E) between 10,703–12,857 ft, in the onshore coastal plain of the Red Sea (Hughes and Johnson, 2005). The Dhaylan Member is found only in the subsurface, where it is commonly conformable on the underlying An Numam Member. The depositional environment of the Dhaylan Member is deep marine based on the regional association with deep-marine, outer neritic to upper bathyal benthonic and planktonic foraminiferal-bearing sediments.

The Wadi Waqb Member is a carbonate unit that is an important hydrocarbon reservoir in the Midyan region. Its exposures are limited to the Wadi Waqb vicinity on the southwestern flanks of Jabal Kibrit and is defined in the Saudi Aramco exploration well Midyan S-1 (MDYN-1: 28°10′34.4″N, 34°52′12.9″E) between 7,000–7,447 ft (447 ft, 136.3 m thick), onshore coastal Saudi Arabian Red Sea. The Wadi Waqb Mbr is conformable with the underlying An Numan Member in the An Numan-1 (type section well for the An Numan Member), and is locally overlain by basinal calcareous mudstones of the Dhaylan Member of the Jabal Kibrit Fm. The carbonates are typically rich in corals and rhodoliths; however, the most common facies is interpreted as deep-marine, planktonic foraminiferal-bearing wackestone matrix containing transported allochthonous bioclasts derived from a shallow-marine carbonate setting.

The An Numan Member is characterized by a predominantly anhydritic lithology and regional subsurface presence. It is easily recognized as the oldest (first) post-Burqan evaporite. The Member is named after the Tenneco exploration well An Numan-1 (ANMN-1), situated offshore in the northern part of the Red Sea. It unconformably overlies the Burqan fm and is conformably overlain by the Wadi Waqb Member of the Jabal Kibrit Mbr. The environment of deposition of the An Numan Member is interpreted as submarine hypersaline within locally restricted basins based on the regional association with deep marine benthonic and planktonic foraminiferal bearing sediments.

An early middle Miocene age (Langhian) was interpreted from the subsurface presence of planktonic foraminifera belonging to Zones N9 and N8 in the upper unit of shales and claystones (Hughes and Filatoff, 1995). Planktonic Foraminiferal Zone N9 (early middle Miocene) was based on the first downhole occurrence of Praeorbulina glomerosa, P. transitoria, and Globigerinoides sicanus with the presence of Orbulina suturalis and Orbulina bilobata. Zone N8 (earliest middle Miocene) was based on the first downhole occurrence of P. glomerosa curva in the absence of Orbulina species. Calcareous nannofossils Sphenolithus heteromorphus in the absence of Helicosphaera ampliaperta indicated Zone NN5 (Hughes and Filatoff, 1995)

"From subsurface evidence, the sediments of the Jabal Kibrit Fm are considered to have been deposited under deep-marine outer-neritic to possible upper-bathyal conditions as indicated by the rich and diverse assemblages of deep-marine planktonic and benthonic foraminifera (Hughes and Filatoff, 1995). Micropalaeontological evidence from the interbedded shales can offer conclusive evidence for a submarine, moderately deep environment for the evaporites. Coarse-grained facies, however, may be the products of penecontemporaneous downslope transport from a shallow-marine source (Wadi Waqb Member). The distribution of the evaporitic An Numan Member suggests local submarine deposition within more restricted basins." (Hughes and Johnson, 2005)