Mishrif Fm
Type Locality and Naming
is in B.P.C. Well Zubair No. 3, in South Iraq. R.M.S. Owen and S.N. Nasr, 1958
Synonym: “Mishrif Formation”, Smout, 1956. “Mishrif Formation”, Dunnington et al, 1959. “Mishrif Formation”, Dominguez, 1965. “Mishrif Member”, Powers et al., 1966. “Mishrif Formation”, Dunnington, 1967.
Reference Section:
Q.P.C. well Dukhan No. 28, lat 25°17’12” N, long. 50°48’36” E, elevation 32 m (106 ft), completed 1.5.1952, between drilled depth 646 and 727m (2118 and 2384 ft).
Lithology and Thickness
Limestone; light grey, soft, porous, shell-fragment, foraminiferal wackestone to packstone. Occasional thin shales towards base. Its thickness is 81 m (266 ft)
Relationships and Distribution
Lower contact
Ahmadi Fm, contact conformable. Placed at the top of the highest well developed shale horizon of the Ahmadi. In Qatar is selected at contact of more or less continuous pure limestone, above, with interbedded shales and limestones of the underlying Ahmadi. Regionally, the formation boundary is diachronous. (see additional information)
Upper contact
Laffan Fm, contact unconformable. At junction of limestones of the Mishrif, with olive-green shales of the overlying Laffan Formation. Crestal cut-out of part of the Mishrif, beneath the Laffan, can be demonstrated on the Dukhan structure. The chronological list of current rock units indicates the next younger unit as Wasia Gr
Regional extent
In deep wells throughout the Qatar peninsula and offshore area. Also known from South Iraq, Kuwait, Saudi Arabia and Abu Dhabi.
GeoJSON
Fossils
Dicyclina qatarensis Henson, Zekritia langhami Henson, Qataria dukhani Henson, Praealveolina Cretacea (d’Archiac), Pseudochrysalidina conica Henson, Dictyoconella minima Henson, Dohaia planata Henson, Cuneolina pavonia d’Orbigny, Meandropsina vidali Schlumberger.
Age
Depositional setting
Additional Information
Originally included in the “Khatiyah Fm” of Dukhan until thicker sections, discovered on the flanks of the structure, proved lithologically and faunally comparable to the typical Mishrif Fm of South Iraq.
The Mishrif Fm thickens eastwards from Dukhan as a result of progressive replacement of shales of the Ahmadi Fm by shelf limestones. In onshore Abu Dhabi no vestige of the Ahmadi remains and the name Mishrif is applied to a very thick shallow-water limestone unit of Cenomanian age.
Faunal evidence suggests that the Mishrif Fm is of Cenomanian age in Qatar. It has been assigned to the Turonian in some neighbouring areas and it is not impossible that rocks of that age could occur in the upper part of the formation in Qatar, in areas where the least erosion has taken place.