Tayran Gr
Type Locality and Naming
The Tayran Group consists of the Al Wajh Fm, Yanbu Fm, and Musayr Fm. Bokhari (1981) first assigned the name Tayran formation after Jabal Tayran, Midyan area, onshore coastal Red Sea. Recent studies of surface and subsurface data have clarified previously inconsistent classification schemes. Column: Red Sea Saudi Arabia
Synonym:
Lithology and Thickness
"Reef and carbonates occurring on submerged paleohighs, shale deposited in zones of slightly deeper water, sands occurring in marginal basins, and isolated evaporites deposited on the central Saudi Arabian Red Sea margin and in the north. … The Tayran Gr consists of conglomerates, sandstones, shallow-marine carbonates, and in the subsurface, anhydrite. Bokhari (1981) divided his formation into three members: (1) the lower Wadi al Hamd member consisting of red siliciclastics; (2) the upper Wadi al Kils member, a shallow-marine carbonate unit; and (3) the Wadi Telah member, a laterally-equivalent, mixed siliciclastic-carbonate unit. Bokhari’s formation formed part of the Raghama Gr (Richter-Bernburg and Schott, 1954) that included the entire ‘Oligocene-Miocene’ succession (Skipwith, 1973; Brown et al., 1989). In the subsurface, it is made up of anhydrite and was referred to as the Sharik Fm by Clark (1986). The Tayran Gr, as currently defined, displays significant lateral and vertical lithological variations. The siliciclastic Al Wajh Fm makes up the entire Tayran Gr at certain subsurface localities but, as exposed in Midyan, is overlain by carbonates of the Musayr Fm. In the subsurface of the Yanbu Basin and elsewhere in the Saudi Arabian Red Sea area, the Al Wajh Fm siliciclastics are often overlain by anhydrite of the Yanbu Fm" (Hughes and Johnson, 2005).
Relationships and Distribution
Lower contact
In the Egyptian Red Sea, the early syn-rift sediments lie with less than 10 degrees of angular unconformity upon a pre-rift sedimentary succession that reaches 2,000 m in thickness (Montanet et al., 1998). The Tayran Group is nonconformable on Proterozoic Basement rocks, both onshore and offshore. Regionally, the schematic strat column of Mideast timescale 2008 indicates the next older unit as the Jizan Gr.
Upper contact
The Tayran Group is probably unconformably overlain by the Burqan Fm, as seen in the Midyan exposures and in the subsurface, where a distinct lithological and paleoenvironmental contrast is evident Regionally, the schematic strat column of Mideast timescale 2008 indicates the next older unit as the Burgan Kibrit Fm
Regional extent
In the Midyan region, the Tayran Group is exposed along the northeastern margin of the Ifal Plain and in the Jabal ar Risha area. Regionally, both the Al Wajh and Yanbu Formations are present in the Al Wajh and Yanbu Basins, and as far south as Jiddah (Figure 1). The Tayran Gr has not been identified in wells drilled in the Ghawwas or Jizan Basins.
The Tayran Gr is correlated to the Nukhul Fm of the Gulf of Suez and Red Sea based on lithological and paleontological similarities (Sellwood and Netherwood; 1984; Hughes et al., 1992; Hughes and Beydoun, 1992; Hughes and Filatoff; 1995; Ravnas and Steel, 1998). It is considered equivalent to the Hamamit Fm of Sudan (Schroeder et al., 1989), the Ranga Fm in the northwest Red Sea (Montanet et al., 1998, their Figure C3.2) and the Nutaysh Fm (Purser and Hotzl, 1988). The Tayran Gr is equivalent to the early syn-rift tectono-sedimentary unit A of Plaziat et al. (1998).
GeoJSON
Fossils
Biostratigraphic studies (Hughes and Filatoff, 1995; Filatoff and Hughes, 1996) suggest an early Miocene age for most of the Tayran Gr with definite evidence of an early Miocene age for the Musayr Fm. Jado et al. (1990), however, provide late Eocene macropaleontological evidence for pre-rift siliciclastics at a small exposure 10 km north of the coastal town of Maqna. If correct, this may indicate the presence of the Shumaysi fm, or time-equivalent sediments, within a succession currently attributed to the Al Wajh Fm in the Midyan region.
Age
Depositional setting
The Tayran Group represents the early syn-rift stage in the evolution of the Red Sea and the progression from a siliciclastic to carbonate, and locally evaporitic, depositional regime resulting from the progressive regional increase of marine influences. The term “proto-rift” has been proposed for this early phase of rift associated sedimentation. The facies deposited during early rifting reflect the paleotopographic irregularities of the Red Sea proto-basin. Hughes and Johnson (2005) interpret contemporaneous deposition of multiple facies as follows: reef and carbonates occurring on submerged paleohighs, shale deposited in zones of slightly deeper water, sands occurring in marginal basins, and isolated evaporites deposited on the central Saudi Arabian Red Sea margin and in the north.
Additional Information