Shirinab Fm
Type Locality and Naming
Holotype section: Shirinab River section. Author: Hunting Survey Corporation, 1960. Reference section: None.
Lithology and Thickness
Limestone. In the type area, the formation consists of limestone with subordinate marl and shale. The limestone is thin- to thick-bedded, grey to dark grey, ash grey, weathers rusty brown to brownish grey, mottled, sub-lithographic, micritic to biomicritic with shelly, oolitic, peletic and pisolitic interbeds. It is also crinoidal, platy, flaggy, dolomitized and argillaceous at places. Coquina beds are common. The marl is greenish grey and nodular. The shale dominates the upper part and is buff, maroon, greenish grey to brown, calcareous, and ranges from soft flaky to hard fissile.
Thickness: 230- >1,000 m More than 1,000 m in the Kallat section, and 230 m (measured, base not exposed) in the Gurruk-Ziarat section.
Relationships and Distribution
Lower contact
Conformably underlain by Malikhore Fm [Note by J.Ogg – this "underlain" is difficult to reconcile with the indicated age-spans of the Shrianab as "pre-Toarcian down to perhaps latest Triassic" and of the Malikhore which is " Early Jurassic"; so perhaps are coeval and facies-migration?]
Upper contact
Conformably overlain by Sembar Fm (transitional), except in type locality where Goru Fm disconformably overlies it with a laterite bed in between. [Note by J.Ogg – Sembar is Early Cretaceous, therefore also difficult to reconcile with the indicated age-spans of the Shrianab as "pre-Toarcian down to perhaps latest Triassic" and of the Malikhore which is " Early Jurassic"; so perhaps are coeval and facies-migration?]
Regional extent
The formation is exposed in the Kallat, Quetta, Zhob and Loralai districts of Balochistan.
GeoJSON
Age
Depositional setting
Additional Information