Ruilat Fm

Period:

Cretaceous

Age Interval:

?Campanian

Province:
Qatar

Type Locality and Naming

Originally described from Q.P.C Well Dukhan No. 25. Another section is now designated the type section. This is Q.P.C. Well Dukhan No. 55, lat. 25°24’0” N, long. 50°43’46” E, elevation 7 m (23 ft), completed 17.8.1956, between drilled depths 501 and 570 m (1644 and 1870 ft).

Synonym:

Reference Section:

Lithology and Thickness

Top. 1. Limestone, light grey, compact, lime mudstone to wackestone, particles consisting of fine elongate spicules; some indeterminate calcareous silt. Chert nodules occur in the upper part of the unit. Fine recrystallisation obscures rare, small foraminifera. 66 m (216 ft). 2. Limestone as above, with common rounded phosphatic nodules and glauconite grains. 3 m (10 ft). Base. Its thickness is 69 m (226 ft).

Lithology Pattern:

Limestone

Relationships and Distribution

Lower contact

Halul Fm, contact unconformable. At the junction of light grey lime mudstones, below, with glauconitic limestone of the basal Ruilat, above. The chronological list of current rock units indicates the next older unit as Fiqa’ Fm

Upper contact

Simsima Fm; conformable contact at boundary between fossiliferous lime packstones of the Simsima Fm, above, with fine grey, spicular lime mudstone of the Ruilat Fm.

Regional extent

Confined to the Qatar peninsula where it has been recorded from all but one well on the Dukhan anticline and from Q.P.C. exploration wells.

GeoJSON

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Fossils

Small unidentified foraminifera.

Age

The age of the Ruilat Formation cannot be determined from its contained fauna but is assumed to be Campanian from its stratigraphical position between proven Maestrichtian limestone and the Halul Formation which has a Santonian to early Campanian age.

Age Span:

Beginning stage:

Campanian

Fraction up in beginning stage:

0.9

Beginning date (Ma):

73.32

Ending stage:

Campanian

Fraction up in the ending stage:

1.0

Ending date (Ma):

72.17

Depositional setting

Depositional pattern:

Additional Information

The Ruilat Fm is known only in onshore Qatar. Correlation with the section in Q.P.C. Well Dukhan No. 51, shows that the Ruilat is the lateral equivalent of all or part of the Fiqa’ Fm and therefore of Campanian age. See Fiqa’ Fm.

Compiler:

Jacques LeBlanc (2021), transcribed and translated from Stratigraphic Lexicon Qatar Peninsula by W.Sugden and A.J. Standring, 1972