Bishima Fm
Period:
Paleogene
Age Interval:
Early Eocene
Province:
Murzuq Basin, Sirte Basin
Type Locality and Naming
A major Paleocene to Early Eocene (Ypresian) stratigraphic unit in Libya
Synonym: also spelled Bishimah Fm, Bisiman Fm
References:
Lithology and Thickness
It mainly consists of shallow-marine carbonates, chalky limestones, dolomites, and marls. The formation is commonly divided into distinct members reflecting restricted platform to shallow shelf depositional settings:
Khayir (Kheir) Member: Lowest unit. Consists largely of marls and shales.
Wadi Zakim Member: Comprises dolomitic chalky limestone and sandy marl with gypsum.
Rawaghah Member: Upper unit. Characterized by shallow-water limestone facies.
Lithology Pattern:
Shallow-marine marl
Relationships and Distribution
Lower contact
It unconformably overlies the Surfah Fm of Thanetian. The contact boundary between the top of the Shurfah Fm and the Bishima strata is widely erosional.
Upper contact
Unconformably overlain by the Bishima Fm of early Eocene.
Regional extent
Prominently exposed in the Sirte Basin, Jabal Waddan, and northwestern areas like Bani Walid. [GeoJSON is only Murzuq Basin, because Sirte Basin has other detailed age units during this same time span.]
GeoJSON
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Fossils
Google Gemini: “Abundant larger benthic foraminifera (such as Alveolina/Flosculina) and localized shark teeth indicating photic zone depths.”
Age
Shown in Fello (2001)’s Repsol regional column as Eocene. Google Gemini: “Spans the Late Paleocene through the Early Eocene (Ypresian), marking key shallow-marine incursions across northern Libya.”
Age Span:
Beginning stage:
Ypresian
Fraction up in beginning stage:
0.00
Beginning date (Ma):
56.00
Ending stage:
Ypresian
Fraction up in the ending stage:
1.0
Ending date (Ma):
48.07
Depositional setting
Google Gemini: “: Deposited in inner-shelf, restricted platform, and sabkha-influenced shallow marine environments associated with changing sea-level cycles in the Mediterranean foreland of the African shield.”
Depositional pattern:
Additional Information
Compiler:
Enam O. Obiosio, Solomon Joshua Avong and Henry Nasir Suleiman (2026). The Cretaceous and Cenozoic entries were mainly taken from AI-assistant summaries of Google’s Gemini (accessed in Aug’2026)