Mesozoic • Jurassic GSP memoir

Chiltan Limestone

Middle to Late Jurassic (Bathonian-Oxfordian)

Cited in 9 sources Last reviewed Aug 2, 2026

Unit summary

Rank: Not recorded
Status: Published
Age: Mesozoic · Jurassic · Middle JurassicMiddle to Late Jurassic (Bathonian-Oxfordian)
Named by: Not recorded
Type locality: Chiltan Peak, near Quetta30.1523°N, 66.9318°E
Thickness: ≈750–1,800 m in the Sulaiman Fold Belt, increasing westward
Lithology: Thick shelf carbonate — pisolitic to oolitic limestone with reefal development in the upper part.
Synonyms: Not recorded

A thick Middle Jurassic oolitic shelf limestone — the main Jurassic carbonate of the region, a gas reservoir, and the floor beneath the Dilband iron ore.

Named after Chiltan Peak near Quetta. Thick carbonate platform sequence forming prominent mountains. Major petroleum reservoir in Sulaiman basin.

Fossils

Corals

Contacts

In the Sulaiman Fold Belt column

Shale / mudLimestoneFossils 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

Sulaiman Fold Belt

Basin: Not recorded
Region: Not recorded
Depositional environment: shallow marine, carbonate platform
Coordinates: 30.1523°N, 66.9318°E

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Correlation

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

Economic significance

Reservoir Metals & minerals

A significant Middle Jurassic hydrocarbon reservoir of the Indus Basin (e.g. Zarghun South gas); its top unconformity hosts the Dilband oolitic iron ore.

Remarks

A thick Middle Jurassic oolitic shelf-carbonate platform sequence (equivalent to the Samana Suk / Takatu / Zidi limestones), the principal Jurassic carbonate of the Kirthar–Sulaiman region and a deep gas reservoir.

Research notes (6)

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 (1)

Kazmi & Abbasi (2008) DUPLICATE FLAG: the book treats the Chiltan Limestone and the Takatu Limestone as the SAME unit (the 'Takatu (Chiltan) Limestone', Middle Jurassic), with the Mazar Drik as its upper member. This record and 'takatu-limestone' are therefore likely duplicates to merge; the book gives Middle Jurassic (no Oxfordian extension).

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

Lithology (1)

Composed of thick, massive-bedded, shoaling-upward carbonate cycles dominated by grainstone (locally oolitic); microfacies range from lime mudstone (MF1) through bioclastic peloidal packstone (MF2) to bioclastic ooidal grainstone (MF3). Laterite and karstification at the top record paleo-exposure that enhances reservoir quality (Iqbal et al. 2012; Memon et al. 2023).

Memon, F.H., Tunio, A.H., Memon, K.R., Mahesar, A.A. & Abbas, G. (2023)

Thickness (1)

Corrected from "420 m (Nabisar well) to over 983 m (Digh well)" (Nabisar/Digh wells, Lower Indus — not supported by the cited source) to the thickness reported by the cited source: "Reported thickness ranges from 750 to 1800 m in the Sulaiman Fold Belt" (map shows westward increase).

Iqbal, M., Nazeer, A., Ahmad, H. & Murtaza, G. (2012)

Type locality & location (1)

Corroborated by USGS OFR 94-689: the Middle Jurassic Chiltan Limestone is mapped in the Chiltan Range southwest of Quetta and southeast of Kach and Gogai.

Maldonado, F., Khan, S.H. & Mengal, J.M. (1994)

Stratigraphic contacts (1)

Umar et al. (2024): the Chiltan Limestone (and equivalent Jurassic carbonates) is overlain disconformably by the Cretaceous Sembar Formation, the contact marked by a lateritic interval; it overlies the Jurassic Shirinab Formation (Razzaq Manan et al. 2024).

Umar, M., Kassi, A.M., Jamil, M., Kasi, A.K. & Khan, A.S. (2024)

Depositional environment (1)

Razzaq Manan et al. (2024): the Chiltan Limestone spans deep-marine, lower-slope pelagic calcisphere wackestone/packstone (SMF-3) up to high-energy ooidal grainstone and peloidal packstone of the agitated inner shelf (SMF-15/16) — a shallowing carbonate ramp. Fracturing, dolomitization and de-dolomitization have locally enhanced secondary porosity, giving reservoir potential in this frontier petroleum belt.

Razzaq Abdul Manan, Kassi, A.M., Friis, H., Kasi, A.K., Ali, S.H., Farooqui, M.A. & Kakar, M.I. (2024)

Sources (9)

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.
Diagenetic and mineralogical impact on the carbonate (Chiltan) Formation of the Indus Basin, Pakistan. Minerals (MDPI), 13(12), 1474 (2023).
Iqbal, M. et al. (2017). Hydrocarbon exploration perspective in Middle Jurassic-Early Cretaceous reservoirs in the Sulaiman Foldbelt, Pakistan. (ResearchGate).
OpenStreetMap contributors and GEOnet Names Server (public geographic gazetteers), used to geolocate named GSP type localities to approximate decimal coordinates.
Maldonado, F., Khan, S.H. & Mengal, J.M. (1994). Preliminary Geologic Map of Parts of Loralai, Sibi, Quetta, and Khuzdar Divisions, Balochistan Province, West-Central Pakistan. U.S. Geological Survey Open-File Report 94-689, 20 p., 1 sheet.
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.
Razzaq Abdul Manan, Kassi, A.M., Friis, H., Kasi, A.K., Ali, S.H., Farooqui, M.A. & Kakar, M.I. (2024). Deposition and diagenesis of the Triassic-Jurassic limestone successions of the northwestern passive margin of the Indian plate, Sulaiman Fold-Thrust Belt, Pakistan. Carbonates and Evaporites, 39, 104.
Umar, M., Kassi, A.M., Jamil, M., Kasi, A.K. & Khan, A.S. (2024). Cretaceous stratigraphic framework and sedimentary architecture, Pakistan: signatures of rift-drift tectonics and submarine volcanism along the western continental margin of the Indian Plate. In: Hart, M.B. et al. (eds) Cretaceous Project 200 Volume 2: Regional Studies. Geological Society, London, Special Publications, 545.

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: Appears in a single-author Geological Survey of Pakistan memoir (Malkani & Mahmood 2017), not cross-confirmed against the Shah lexicon. The Stratigraphic Committee of Pakistan is largely inactive, so documented provenance — not formal ratification — is the available signal.

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Cite this unit

APA

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

BibTeX

@misc{stratigraphypk_chiltanlimestone,
  author    = {Qudsi, Lareb},
  title     = {{Chiltan 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/chiltan-limestone (accessed October 29, 2026).

Below · older

Shirinab Formation

Triassic-Jurassic

Above · younger

Sembar Formation

Cretaceous

Referenced in other successions

Overlain by Dilband Formation· Mazar Drik Formation

Underlain by Anjira Formation· Loralai Formation