Cenozoic • Paleogene In GSP lexicon

Shekhan Formation

Early Eocene (Ypresian)

Kohat sub-basin, Khyber Pakhtunkhwa

Cited in 6 sources Last reviewed Jul 17, 2026

Unit summary

Rank: Not recorded
Status: Published
Age: Cenozoic · Paleogene · EoceneEarly Eocene (Ypresian)
Named by: Davies (1926b); raised to formation rank by Cheema et al. (1977)
Type locality: Shekhan, Kohat
Thickness: ~32 to 44 m (Sheikhan Nala and Panoba sections); age-diagnostic foraminiferal zone ~9 to 30 m
Lithology: Compacted, yellowish-grey, medium- to thin-bedded fossiliferous limestone with shale partings, plus subordinate shale and sandstone; micrite-dominated.
Synonyms: Sheikhan Limestone (alternative spelling); Drug Formation (Sulaiman Basin), lateral equivalent; Sakesar / Margala Hill Limestone (Potwar and Hazara), lateral equivalent

A yellow-grey nodular Eocene limestone of the Kohat area, lying just above the Panoba shale.

The Shekhan Formation (also spelled Sheikhan Limestone) was named after Sheikhan Nala by Davies (1926b) and formalised as a formation by Cheema et al. (1977). It is an Early Eocene (Ypresian) unit of the Kohat sub-basin: compacted, yellowish-grey, medium- to thin-bedded fossiliferous limestone with shale partings and subordinate shale and sandstone, about 32 to 44 m thick at its main sections. Its larger foraminifera (Orbitolites complanatus, Alveolina, Assilina and Nummulites atacicus) indicate shallow-benthic zones SBZ 5-7 and an Early Eocene age. It is the lateral equivalent of the Sakesar/Margala Hill Limestone of the Potwar and Hazara basins and of the Drug Formation of the Sulaiman Basin. Part of the Panoba Group.

Fossils

Orbitolites complanatus Alveolina oblonga Alveolina vredenburgi Assilina daviesi Assilina laminosa Assilina dandotica Nummulites atacicus Corals Gastropods Echinoids Discocyclina dispensa Discocyclina fortsi Assilina exponens Nummulites

Contacts

Lower contact — conformable; upper contact — not recorded.

In the Kohat Basin column

SandstoneShale / mudLimestoneGypsum / evaporiteFossils recordedConformable

Band colour = period; texture = dominant rock type. Lines between bands mark the contact type. True scale makes height ∝ recorded thickness; hatched = thickness not recorded. Ages approximate, for ordering.

This unit (highlighted) within its province column; faded ends continue above and below. Line style marks the contact type.

Distribution & setting

Kohat Basin

Basin: Not recorded
Region: Kohat sub-basin, Khyber Pakhtunkhwa
Depositional environment: Shallow marine carbonate shelf, Inner ramp
Coordinates: Not recorded

Correlation

Not recorded. Compare this unit against other basins on the correlation panel →

Economic significance

Reservoir Salt & evaporites

Studied as a fractured carbonate reservoir target in the Kohat Basin; spatially associated with the Bahadurkhel (Kohat) evaporite system.

Remarks

The Kohat-basin representative of the Early Eocene shallow-marine carbonate that is elsewhere the Sakesar/Margala Hill Limestone; its larger foraminifera place it in shallow-benthic zones SBZ 5-7, constraining the late marine phase of eastern Tethys in northwest Pakistan.

Research notes (3)

Field-by-field findings drawn from the cited literature. Every statement is traced to a registered source — follow a citation for the full reference.

Age & correlation (2)

Afzal, Williams & Aldridge (2009) assign the Shekhan Formation a late Ypresian age: shallow benthonic Zone SBZ11 (Nagappa 1959; Pascoe 1963; Shah 1977; Weiss 1993), with Assilina laxispira and the planktonic foraminifera Morozovella aragonensis indicating planktonic Zones P8-P9 (Meissner et al. 1974). It is barren of nannofossils and dinoflagellates. Refines the curated Early Eocene age to late Ypresian.

Afzal, J., Williams, M. & Aldridge, R.J. (2009)
Ahmad, Kroon, Rigby & Khan (2016, Stratigraphy 13(4)) record the Sheikhan Formation (Sheikhan Nala, Kohat Basin) within their BFZ 3 Zone (~22 m thick), with figured Orbitolites complanatus and flosculinized Alveolina pasticillata - an early Eocene (Middle Ilerdian 2-Middle Cuisian, SBZ 8-11) assemblage that conformably overlies the Panoba Shale. Corroborates the curated Early Eocene age.

Ahmad, S., Kroon, D., Rigby, S. & Khan, S. (2016)

Fossils & biostratigraphy (1)

Larger benthic foraminifera identified at the Panoba section: Discocyclina dispensa, D. fortsi, Assilina dandotica, A. exponens, Alveolina vredenburgi and Nummulites, with three planktonic-foraminiferal biozones and Alveolina/Assilina zones (Hottinger) indicating an Early–Middle Eocene, inner-shelf setting (Khan et al. 2019).

Khan, S., Rashid, M.U. & Haider, N. (2019)

Sources (4)

Reviewer confidence: high

Every fact on this page is source-cited. This entry is part of the peer-archived Pakistan Stratigraphy Dataset (doi.org/10.5281/zenodo.21363991, CC‑BY‑4.0).

Lexicon status: Name attested in the Shah (1977/2009) Geological Survey of Pakistan compilation — the national stratigraphic lexicon. This records where the name is documented; it is not an endorsement of the unit’s definition, age or figures.

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Cite this unit

APA

Qudsi, L. (2026). Shekhan Formation. In Pakistan Stratigraphy Dataset [Data set]. Zenodo. https://doi.org/10.5281/zenodo.21363991

BibTeX

@misc{stratigraphypk_shekhanformation,
  author    = {Qudsi, Lareb},
  title     = {{Shekhan Formation} --- Pakistan Stratigraphy Dataset},
  year      = {2026},
  publisher = {Zenodo},
  doi       = {10.5281/zenodo.21363991},
  url       = {https://doi.org/10.5281/zenodo.21363991}
}

Archived dataset: doi.org/10.5281/zenodo.21363991 (CC‑BY‑4.0) · Direct link to this entry: https://stratigraphy.pk/formation/shekhan-formation (accessed October 7, 2026).

To cite the unit's original definition instead, see: Davies (1926b); raised to formation rank by Cheema et al. (1977).

Below · older

Gurguri Formation

Paleogene

Above · younger

Bahadurkhel Salt