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Bir Hacheim Formation
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Bir Hacheim Fm base reconstruction

Bir Hacheim Fm

Period: 
Cretaceous

Age Interval: 
Aptian-Albian


Province: 
Cyrenaica Basin

Type Locality and Naming

“The Bir Hacheim Formation (sensu stricto) is a well-established Lower Cretaceous subsurface unit named after the Bir Hakeim area on the Cyrenaica Platform and recognized in formal stratigraphic frameworks across northeastern Libya (including the Cyrenaica Basin and eastern Sirt Basin).” (Google Gemini overview).

Synonym: Bir Hakeim Fm, Bir Hacheim Shale Fm; Daryanah Fm (used on chart of El Oshebi and Fares, 2026; but Google Gemini overview was unable to verify use of this name.

References: El Oshebi and Fares (2026). and Google Gemina (Aug’26)


Lithology and Thickness

Shale (diagram of El Oshebi and Fares, 2026). “Composed predominantly of dark gray, pyritic, and carbonaceous marine shales and mudstones, with interbedded thin siltstones, fine-grained sandstones, and occasional argillaceous limestone or dolomite stringers. … It is a Source Rock -- The organic-rich, dark shaly intervals within the formation serve as localized, mature-to-immature petroleum source rocks (predominantly Type II/III kerogen capable of generating gas and light oil). .. In addition to being a Regional Seal -- Due to its low permeability and lateral extent across the platform and basin edges, the Bir Hacheim Shale acts as a major top seal for underlying Lower Cretaceous reservoir sandstones.” (Google Gemini overview)


Lithology Pattern: 
Claystone


Relationships and Distribution

Lower contact

Conformable onto the Qahash Fm (stratigraphic diagram in El Oshebi and Fares, 2026)

Upper contact

Unconformably (lower Cenomanian is absent) overlain by the Qasr Al Abid Fm according to Shaltami et al. (2020).

Regional extent


GeoJSON

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Fossils


Age 

Spans the Aptian-Albian according to the stratigraphic diagram in El Oshebi and Fares (2026). The underlying Qahash Fm seems to include earliest Aptian palynology; therefore base is put into early Aptian.

Age Span: 

    Beginning stage: 
Aptian

    Fraction up in beginning stage: 
0.2

    Beginning date (Ma): 
119.76

    Ending stage: 
Albian

    Fraction up in the ending stage: 
1.0

    Ending date (Ma):  
100.50

Depositional setting

“Represents a major Early Cretaceous regional transgression. It was deposited in restricted-marine, shelf-lagoonal, to dysoxic outer-shelf environments as rising sea levels flooded low-lying rifted topography across the North African margin.” (Google Gemini overview)


Depositional pattern:  


Additional Information

:


Compiler:  
s:

Shaltami, O.R., et al. (2020). Petroleum system of the Cyrenaica Basin – A review. In: 1st International Symposium on Geosciences (ISG2020), 21th March 2020, Proceeding Book: published by BR Petrobras. P. 64-71.

Tawadros, E.E. (2011). Geology of North Africa. CRC Press (Taylor & Francis Group), 931 pp.

Google Gemini (Aug 2026) – assembled synthesis of Cyrenaica Basin units from various web-accessible publications.

El Oshebi, F.M., Fares, F.F. (2026). Stratigraphy, facies, and depositional environments of the Eocene sequence in the Ras Al Hilal area, Cyrenaica, Libya. Arabian Jour. Geosciences, 19:79. https://doi.org/10.1007/s12517-026-12488-2.

El-Hawat, A.S., Abdulsamad, E.O. (2004) Geology and Archeology of Cyrenaica, Northeastern Libya. Field trip guide B01, 32nd International Geological Congress. 36 pp.