Kharaib Fm
Type Locality and Naming
The Kharaib is part of the extensive shallow marine shelf system that was established in Early Cretaceous times following the rapid progradation of the Rayda Fm – Salil Fm - Habshan Fm. Column: Oman Subsurface, Bahrain, Qatar, United Arab Emirates; Contains the Hawar Mbr, Upper Kharaib, and Lower Kharaib Mbr.
The type section is Kharaib-1 in Qatar (Sugden and Standring, 1975). The reference section in Oman is well Lekhwair-7.
Synonym:
Lithology and Thickness
Limestone. Lithologically the Formation is very comparable to the overlying Shu’aiba Fm and the underlying Lekhwair Fm. Commonly divided into an upper Hawar Mbr and a Lower Kharaib Mbr. "The Kharaib Formation is essentially a clean carbonate unit composed of mudstones, with oncoidal and binding algae in the lower part and packstones/grainstones with common rudists in the upper part. It is capped by a thin, hard limestone unit; the Hawar Member.. . . The thickness of the Hawar Member is variable and on a regional scale shows a trend from a few meters in the Greater Lekhwair area in the northwest to some 10–20 m along the eastern edge of the Ghaba Salt Basin. Also towards the Al Hajar Mountains the interval assigned to the Hawar reaches a thickness of up to 25 m (van Buchem et al., 2002). It is a lithologically heterogeneous interval of clay- free limestones, which vary from shallow-marine mudstones to grainstones, locally rich in rudists, to intertidal deposits with wave ripples laminites, mud-cracks, rip up clasts (van Buchem et al., 2002). Towards the Al Huqf High area, the Hawar interval becomes more open marine in character with common corals and echinoids and represents a deeper lagoon setting."
Relationships and Distribution
Lower contact
Regionally, it is conformable onto the Lekhwair Fm
Upper contact
Regionally, it is conformable below the Shu'aiba Fm. Immenhauser et al. (2004) apply both biostratigraphic and chemostratigraphic techniques to infer an earliest Aptian age for the Kahraib Fm / Shu’aiba Fm boundary by dating Kahraib's Hawar Member equivalent in outcrop as earliest Aptian. In Oman subsurface, the upper boundary is defined by the hard, high Gamma limestone of the Hawar Member below the clean, basal Shu’aiba Fm. In outcrop the Hawar Member corresponds to a decimeter-bedded orbitolinid interval that separates the more massive bedded Shu’aiba Fm and Upper Kharaib Fm limestone beds (van Buchem et al., 2002).
Regional extent
Oman Subsurface, Bahrain, Qatar, United Arab Emirates. The Kharaib is widespread and easily correlatable over much of Oman, with facies indicative of a uniform shallow-shelf sea. It is absent by erosion of younger unconformities in the south and east.
GeoJSON
Fossils
Biozone F55 (Choffatella decipiens, Salpingoporella dinarica) is divisible into Sub-biozones F557 (Choffatella decipiens, Salpingoporella dinarica) and F553 (Salpingoporella muehlbergii). Paleodictyoconus arabicus, the Late Barremian index species of Simmons (1994) has its top occurrence within Sub-biozone F557.
Age
Depositional setting
Uniform shallow-shelf sea. "The sediments and fossils suggest a shallow-marine setting throughout. The rapid progradation of the Habshan Fm (Valanginian-Hauterivian) created an extensive shallow shelf area. The subsequent transgression of the Kharaib Fm started with a microbial/algal carbonate system followed towards the top by a lateral prograding rudist carbonate system. The Hawar Member capping the Kharaib Fm is particularly argillaceous in offshore UAE and Qatar (Alsharhan and Nairn, 1997), but spectral Gamma-ray logs and XRD analyses indicate that true clay intervals are not present in Oman. The depositional setting of the Kharaib Fm is very comparable to that of the overlying Shu’aiba Fm
Additional Information