Cenozoic • Paleogene In GSP lexicon

Pirkoh Formation

Middle Eocene

Part of Early-Middle Eocene Kahan Group, Kahan Group, Kirthar Group

Paleogene in the time scale →

Cited in 6 sources Last reviewed Jul 30, 2026

Unit summary

Rank: Not recorded
Status: Published
Age: Cenozoic · Paleogene · Middle EoceneMiddle Eocene
Named by: Hemphill et al. (1973)
Type locality: Pirkoh anticline
Thickness: 10–175 m
Lithology: Brown, grey to white, thin-bedded limestone with subordinate argillaceous limestone and dark-grey calcareous claystone.
Synonyms: Not recorded

A fossil-rich Middle Eocene limestone of the Kirthar Group and a key gas reservoir (Pirkoh field).

Named after Pirkoh area. Marine sequence in southernmost Kohat region. Part of the Kahan Group.

Fossils

Foraminifera Gastropods Bivalves Echinoids

Contacts

In the Kohat Basin column

LimestoneShale / mudMarlFossils recordedContact not recorded

Band colour = period; texture = dominant rock type. Lines between bands mark the contact type; dotted = no contact recorded in the sources (not a claim of conformity). 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: Not recorded
Depositional environment: shallow marine
Coordinates: Not recorded

Correlation

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

Economic significance

Reservoir

The Pirkoh Limestone is a significant gas reservoir (Pirkoh gas field).

Remarks

A highly fossiliferous Middle Eocene limestone of the Kirthar Group and a major gas reservoir in the Sulaiman province.

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.

Name & nomenclature (1)

Attested in Shah (2009), Geological Survey of Pakistan Memoir 22 - the Stratigraphic Committee's compiled lexicon. Adds the definitional GSP/SCP lexicon citation.

Shah, S.M.I. (2009)

Age & correlation (1)

Jones (1997), Pir Koh Limestone (Kirthar Formation member): 'mid' Middle Eocene, from the nummulitids Assilina exponens and Nummulites beaumonti (Lutetian Moyen–Biarritzian of Schaub 1981; NP15–NP18), planktonic foraminifera Globorotalia (Acarinina) ex gr. bullbrooki (P8b–P12) and Orbulinoides beckmanni (P13), and nannofossils Chiasmolithus grandis and Sphenolithus predistensus.

Jones, R.W. (1997)

Geological significance (1)

Jones (1997): the Pir Koh Member is associated with the transgressive third-order sequence TA3.5 of Haq et al. (1987), spanning laminated shale through mudstone to limestone across carbonate-platform and basinal sub-environments.

Jones, R.W. (1997)

Sources (5)

Malkani, M.S. & Mahmood, Z. (2017). Stratigraphy of Pakistan. Geological Survey of Pakistan, Memoir Vol. 24.
Kazmi, A.H. & Jan, M.Q. (1997). Geology and Tectonics of Pakistan. Graphic Publishers, Karachi.
Indian Plate Lexicon (indplex.geolex.org), Geological Society of India and international compilation.
Shah, S.M.I. (2009). Stratigraphy of Pakistan. Geological Survey of Pakistan, Memoir Vol. 22.
Jones, R.W. (1997). Aspects of the Cenozoic stratigraphy of the Northern Sulaiman Ranges, Pakistan. Journal of Micropalaeontology, 16(1), 51-58.

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). Pirkoh Formation. In Pakistan Stratigraphy Dataset [Data set]. Zenodo. https://doi.org/10.5281/zenodo.21363991

BibTeX

@misc{stratigraphypk_pirkohformation,
  author    = {Qudsi, Lareb},
  title     = {{Pirkoh 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/pirkoh-formation (accessed October 29, 2026).

To cite the unit's original definition instead, see: Hemphill et al. (1973).

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