Paleozoic • Silurian–Devonian formation In GSP lexicon

Shagai Limestone

Silurian(?)–Early Devonian

Northern Indus Suture

Silurian–Devonian in the time scale →

Cited in 6 sources Last reviewed Jul 31, 2026

Unit summary

Rank: formation
Status: Under review
Age: Paleozoic · Silurian–Devonian · Silurian(?)–Early DevonianSilurian(?)–Early Devonian
Named by: Stauffer (1968)
Type locality: 1 km northeast of Shagai, Khyber Pass34.0172°N, 71.2800°E
Thickness: up to ~33 m
Lithology: Grey to black, partly brown limestone, thin- to thick-bedded, locally dolomitic and highly fractured, with thinly laminated limestone and sheared shale at the top.
Synonyms: Not recorded

A grey-to-black Silurian–Early Devonian limestone of the Khyber Pass, below the Ali Masjid Formation.

Fossils

Not recorded

Contacts

In the Khyber–Nowshera Belt column

LimestoneMetamorphicMixedContact 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

Khyber–Nowshera Belt

Basin: Northern Indus Suture
Region: Not recorded
Depositional environment: marine
Coordinates: 34.0172°N, 71.2800°E

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Correlation

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

Economic significance

Not recorded

Remarks

A largely unfossiliferous limestone of the Khyber Agency, exposed between the eastern Khyber Pass, Shagai Fort and Ali Masjid and in tectonic contact with the Khyber carbonate complex; its conformable contact beneath the Late Devonian Ali Masjid Formation makes it Silurian(?) to Early Devonian.

Research notes (5)

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 of Pakistan's compiled lexicon (listed in the memoir's contents). Adds the definitional GSP/SCP lexicon citation.

Shah, S.M.I. (2009)

Age & correlation (3)

Kazmi & Jan (1997): named the 'Shagai Limestone' (Stauffer 1968b) — a rank/name correction for the DB record — this grey-to-black, locally dolomitic, thin- to thick-bedded/massive limestone (unfossiliferous, capped by laminated limestone and sheared shale) is considered Silurian(?) to Early Devonian (Shah et al. 1970), matching the curated age. Type locality 1 km NE of Shagai (Khyber Pass, between Shagai Fort, Ali Masjid and Tauda Mela); in tectonic contact with the overlying Khyber carbonate complex and in conformable contact with the overlying Late Devonian Ali Masjid Formation.

Kazmi, A.H. & Jan, M.Q. (1997)
Molloy, Talent & Mawson (1997): the Shagai Limestone is a persistent unit of up to ~33 m of limestones (with subordinate shale) whose stratigraphic position lies below the Ali Masjid Formation and above the Landi Kotal Formation in the Khyber sequence (Stauffer 1968a; Shah 1977; Shah et al. 1980). Consistent with the curated Silurian(?)–Early Devonian age; the unit itself yielded no diagnostic conodonts in this study.

Molloy, P.D., Talent, J.A. & Mawson, R. (1997)
Kazmi & Abbasi (2008) COMPETING INTERPRETATION (not applied): the book (Pogue et al. 1999) treats the Shagai Limestone as Precambrian (older than the ~750 Ma Khyber Limestone) and places it in its Precambrian chapter, versus the classic Silurian(?)–Early Devonian age. The curated Silurian–Devonian age is retained (consistent with the adjacent conodont-dated Ali Masjid Formation); the Precambrian reassignment is noted as an unresolved alternative.

Kazmi, A.H. & Abbasi, I.A. (2008)

Thickness (1)

Thickness surfaced from the age note: the Shagai Limestone is a persistent unit up to ~33 m of limestones with subordinate shale (Molloy, Talent & Mawson 1997).

Molloy, P.D., Talent, J.A. & Mawson, R. (1997)

Sources (6)

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.
OpenStreetMap contributors and GEOnet Names Server (public geographic gazetteers), used to geolocate named GSP type localities to approximate decimal coordinates.
Shah, S.M.I. (2009). Stratigraphy of Pakistan. Geological Survey of Pakistan, Memoir Vol. 22.
Molloy, P.D., Talent, J.A. & Mawson, R. (1997). Late Devonian-Tournaisian conodonts from the eastern Khyber region, north-west Pakistan. Rivista Italiana di Paleontologia e Stratigrafia, 103(2), 123-148.
Kazmi, A.H. & Abbasi, I.A. (2008). Stratigraphy and Historical Geology of Pakistan. Department & National Centre of Excellence in Geology, University of Peshawar, Peshawar. 524 pp. ISBN 978-969-9119.

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

BibTeX

@misc{stratigraphypk_shagaiformation,
  author    = {Qudsi, Lareb},
  title     = {{Shagai Limestone} --- 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/shagai-formation (accessed October 29, 2026).

To cite the unit's original definition instead, see: Stauffer (1968).

Below · older

Nowshera Formation

Devonian

Above · younger

Ali Masjid Formation

Devonian–Carboniferous