Musayr Fm
Type Locality and Naming
Youngest unit of the Tayran Gr. Clark (1986) informally named the carbonates in the Jabal Musayr region as the Musayr Formation. Type Section: An almost complete Musayr section of well-bedded carbonate (323 ft thick) is found in Wadi Al Hamd dipping at 33° to the northeast (N35°E). Column: Red Sea Saudi Arabia (although it is localized within it.) Uppermost formation in Tayran Gr
Synonym: Previously been considered as the Wadi Al Kils member of the Tayran Fm by Dullo et al. (1983)
Lithology and Thickness
It consists of shallow-marine carbonates that are locally developed. The Musayr Formation consists of a basal calcareous sandstones overlain by skeletal grainstone and pack/wackestone carbonates. An almost complete Musayr section of well-bedded carbonate (323 ft thick) is found in Wadi Al Hamd dipping at 33° to the northeast (N35°E).
Relationships and Distribution
Lower contact
Regionally, the adjusted schematic strat column for graphic purposes would assign the next older unit as Yanbu Fm. However, " There is no evidence that the Musayr Fm overlies evaporites of the Yanbu Fm. Instead, it probably correlates to the upper portion of the Yanbu Fm. .. The Musayr m overlies the Proterozoic Basement at the south flank of Jabal Ar Risha (28°17.00’N, 34°45.21’E) and disconformably overlies the Al Wajh Fm at Wadi Al Hamd.
Upper contact
It is unconformably overlain by the Burqan Fm, as evidenced in the wellexposed contact relationship between the two formations in the vicinity of the eastern entrance to Wadi Al Hamd.
Regional extent
"The Musayr Formation is restricted to the Midyan region where its distinctive carbonate succession crops out on the flanks of Jabal Musayr and where contacts with the underlying Al Wajh Formation are well exposed. The Musayr Limestone forms distinctive escarpments on the northern flank of Jabal Tayran. The carbonates are particularly well exposed and accessible in Wadi Al Hamd (28°23′55.9″N, 34°54′04.2″E) and also in Wadi Al Kils. At Wadi Al Hamd, the Musayr Formation directly overlies the Proterozoic Basement, and the transitional basal beds consist of calcareous sandstone that grade vertically into a sequence of skeletal grainstones and packstones. At this locality, the gorge wall is characterized by recessive oyster beds that alternate with more resistant massive beds (Figure 48) (R.A Kamal and G.W. Hughes, 1993a, Saudi Aramco Report). At the Jabal Musayr locality, large compound corals derived from the Musayr Fm are scattered along the foot of the mountain. . . .
The Musayr Formation is equivalent to the Gharamul Member of the Nukhul Fm in the Gulf of Suez (Saoudi and Khalil, 1983), and the informal Wadi Al Kils member of the Tayran Fm (Dullo et al., 1983), and the Ubbur Fm of Spencer (1987)." (Hughes and Johnson, 2005)
GeoJSON
Fossils
Rich in both macro- and micro-fauna. "The presence of the benthonic foraminiferal genera Miogypsinoides and Miogypsina, including Miogypsina tani, within the carbonates indicate an early Miocene age for the Musayr Fm, equivalent to the Tertiary Upper Te Letter Stage (Adams, 1970; Boudagher-Fadel and Banner, 1999). The late Oligocene age suggested by Dullo et al. (1983) is based on larger benthonic foraminiferal specimens misidentified as Nummulites fichteli, whose illustrated thin sections (Dullo et al., 1983; his Figures 1–4) have been re-assigned to Operculinella venosa in this study. Oysters are a characteristic bio-component of the Musayr Fm and are well represented at the Wadi Al Hamd locality (Figure 48) and on the south flank of Jabal Ar Risha. . . . In contrast to the other formations of the Tayran Group, dinoflagellate cysts are prominent in the palynoflora recovered from the Musayr Formation, and are species of Systematophora and Polysphaeridium." (Hughes and Johnson, 2005)
Age
Depositional setting
The depositional environment of the basal calcareous sandstones of the Musayr Formation is intertidal. The oyster beds, corals, and miogypsinid assemblages in the overlying carbonate rocks indicate a warm, shallow marine environment, such as a shallow marine carbonate platform.
Additional Information