Lower Fars Fm
Type Locality and Naming
H.G. Busk and N.T. Mayo, 1918 (first published reference). The Lower Fars Formation is a subdivision of the Fars Series, first defined by G.E. Pilgrim, 1908 in the Fars Province of Iran.
Synonym: ?”Hadrukh Formation” and “Dam Formation”, Steineke, Bramkamp and Sander, 1958. “Fars”, Dominguez, 1965.
Reference Section:
Jebel Naksh, lat. 24°52’ N, long. 50°54’ E, approx. This is the best exposed section in the area mapped by Q.P.C.
Lithology and Thickness
Top. 1. Chalky limestone, chalky marls and marl varicoloured. Some beds of harder, sometimes shelly or oolitic limestone. Three thin beds of pure gypsum occur towards the middle, together with gypseous marls and chalks. An 8 ft bed of sandy limestone occurs at the top. 49 m (161 ft). 2. Varicoloured marls, partly sandy with interbedded sandy limestone, sandstone and shale. Thin limonitic beds and nodules occur in marls towards the base. 25 m (82 ft). Base. Its thickness is Ca. 79 m (260 ft).
Relationships and Distribution
Lower contact
Dammam Fm; contact obscured at type locality but, nearby, sandy and marly basal Fars beds, containing scattered quartz and igneous pebbles, overlie the Dammam limestones unconformity but without noticeable discordance in individual outcrops. The chronological list of current rock units indicates Hasa Gr.
Upper contact
None. A thin layer of loose gravel caps the Miocene of Jebel Naksh and nearby outcrops.
Regional extent
Exposed in minor synclines in the Dammam Formation in south Qatar and on the flanks of the southern part of the Dukhan structure.
In Bahrain, sandy limestone, soft grey clays and marls, assigned to the Miocene, are believed to be equivalent to the Lower Fars.
The equivalent of the Lower Fars of Qatar should probably be sought in the Dam Formation of neighbouring Saudi Arabia, which yields a similar fauna and has been compared (R.W. Powers, 1968) with the Lower Fars Formation.
The Lower Fars of Qatar passes eastwards into the thick Fars succession seen in offshore Qatar and the Trucial States, where it is predominantly formed of gypsum-anhydrite.
GeoJSON
Fossils
In 1. Dendritina rangii d’Orbigny. Archais sp. In 2. Ostrea Latimarginata Vredenburg. Placuna sp., Discorbis sp., D. rangii.
Age
Depositional setting
Additional Information
The Miocene sediments of Qatar are a marginal development of the thicker more typical Fars deposits which occur in neighbouring areas. The unit can be traced in a continuous development to its type area in Iran.
The name Lower Fars was first used in Qatar by Shaw and Cox in 1933 and has been retained ever since. Its synonymy with the Dam Formation of Saudi Arabia is suggested by the use of that name for the Miocene of South Qatar on U.S.G.S. Geological Maps.