Zman Formation

Zman Fm

Period:

Cretaceous, Paleocene

Age Interval:

Maastrichtian through early Paleocene

Province:
Murzuq Basin, Sirte Basin

Type Locality and Naming

Synonym: often spelled Zimam Fm

References:

Lithology and Thickness

It records important shallow marine transgressive-regressive sedimentary cycles across the Cretaceous-Paleogene boundary. From oldest to youngest, the formation is typically divided into three primary members:

Lower Tar Member: Late Cretaceous (Maastrichtian) age. Composed of marls and limestones rich in foraminifera.

Upper Tar Member: Early Paleocene (Danian) age. Characterized by small benthic foraminifer. [“The transition between the Lower Tar and Upper Tar members helps geologists pinpoint the boundary extinction event and sea-level changes between the Mesozoic and Cenozoic eras in North Africa.”]

Had Member: Middle Paleocene (Selandian) age. Consists predominantly of limestone units marking the upper sequence of the formation's second major depositional cycle.

Lithology Pattern:

Clayey limestone

Relationships and Distribution

Lower contact

It unconformably overlies the Messak Fm (Alpine unconformity – Marzo and Ramos, 2003).

Upper contact

Overlain by the Surfah Fm of Thanetian dolomitic limestone.

Regional extent

Found extensively in northwestern Libya and the Sirte/Hun Graben basin areas.

GeoJSON

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Fossils

Benthic foraminifera: Lower Tar Mbr has larger benthic foraminifera (Omphalocyclus macroporus and Siderolites calcitrapoides) and small planktonic species. Upper Tar Mbr is characterized by small benthic foraminifera such as Neoeponides duwi and Cibicides cf. libycus.

Age

Shown in Fello (2001)’s Repsol regional column as Upper Cretaceous. Google Gemini review narrows to Maastrichtian through Selandian.

Age Span:

Beginning stage:

Maastrichtian

Fraction up in beginning stage:

0.00

Beginning date (Ma):

72.17

Ending stage:

Selandian

Fraction up in the ending stage:

1.0

Ending date (Ma):

59.24

Depositional setting

Shallow-marine carbonate platform.

Depositional pattern:

Additional Information

Outcrops of the formation (such as around Bani Walid) feature well-bedded limestones and gypsum-rich layers suitable for regional construction materials and industrial mineral extraction, alongside localized celestite mineralization.

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)