Cenozoic • Paleogene formation In GSP lexicon

Sui Main Limestone Formation

Early Eocene (Ypresian) (Ypresian; ~56-52.83 Ma)

Cited in 6 sources Last reviewed Jul 30, 2026

Unit summary

Rank: formation
Status: Published
Age: Cenozoic · Paleogene · Early Eocene (Ypresian)Early Eocene (Ypresian) (Ypresian; ~56-52.83 Ma)
Named by: Not recorded
Type locality: Well Sui-36
Thickness: 152-486 m
Lithology: Limestone. At its type section Sui Main Limestone is composed entirely of limestone with minor dolomite, calcareous shales and marls. The limestone is creamy white to dirty white to off white in color. It is firm to moderately hard, occasionally soft, sub blocky to blocky, micro to cryptocrystalline and chalky in parts. The proposed formation represents a rich bioclastic limestone. It consists mo…
Synonyms: Not recorded

Limestone. At its type section Sui Main Limestone is composed entirely of limestone with minor dolomite, calcareous shales and marls. The limestone is creamy white to dirty white to off white in color. It is firm to moderately hard, occasionally soft, sub blocky to blocky, micro to cryptocrystalline and chalky in parts. The proposed formation represents a rich bioclastic limestone. It consists mostly of fine grained lime wackstone, packstone and grainstone. Sedimentary structures are almost entirely of burrows, bioturbation and nodular bedding, although vugs occur rarely. Pyrite crystals are …

Fossils

Not recorded

Contacts

In the Sulaiman Fold Belt column

Shale / mudSandstoneLimestoneFossils 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: Not recorded

Correlation

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

Economic significance

Reservoir

Major gas reservoir at the Sui, Kandhkot and related fields; named by PPL. Subsurface type section at Sui.

Remarks

The lower Eocene (Ypresian) Sui Main Limestone is the most prolific gas reservoir in Pakistan south of ~29°N, with more than 20 tcf of recoverable gas across 14 discovered fields (Siddiqui 2004). It does not outcrop anywhere in Pakistan and is known only in the subsurface; reservoir-quality carbonate development is restricted, diminishing northward as clastic influx increases toward the Sulaiman Range and the Jaisalmer basin.

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's compiled lexicon. Adds the definitional GSP/SCP lexicon citation.

Shah, S.M.I. (2009)

Age & correlation (1)

Corroborated by Siddiqui (2004), AAPG Bulletin: the Sui Main Limestone is lower Eocene (Ypresian), consistent with the dataset's existing assignment. A closed-system carbonate reservoir; the paper analyses its original formation pressures across the central Indus fields.

Siddiqui, N.K. (2004)

Economic significance (3)

Kazmi & Jan (1997): the Eocene Sui Main Limestone is referred to informally as the 'Sui Main/Habib Rahi Limestone' and equated with the Habib Rahi Limestone — an important petroleum reservoir in the Kirthar depression and Sukkur Rift zone; the book does not describe it as a separately named formation.

Kazmi, A.H. & Jan, M.Q. (1997)
Siddiqui (2004) quantifies the reservoir: >20 tcf recoverable gas across 14 discovered fields, the most prolific reservoir south of ~29°N. Recorded alongside the existing Sui/Kandhkot note; the field is not overwritten.

Siddiqui, N.K. (2004)
The lower Eocene (Ypresian) Sui Main Limestone is the most prolific gas reservoir in Pakistan south of ~29°N, with recoverable reserves exceeding 20 tcf across 14 discovered fields; it is a closed-system reservoir that does not crop out, and its chronostratigraphic equivalent on the Kirthar/Punjab platform is the (non-reservoir) Laki Formation (Siddiqui 2004).

Siddiqui, N.K. (2004)

Sources (5)

Indian Plate Lexicon (indplex.geolex.org), Geological Society of India and international compilation.
Kadri, I.B. (1995). Petroleum Geology of Pakistan. Pakistan Petroleum Limited, Karachi.
Shah, S.M.I. (2009). Stratigraphy of Pakistan. Geological Survey of Pakistan, Memoir Vol. 22.
Kazmi, A.H. & Jan, M.Q. (1997). Geology and Tectonics of Pakistan. Graphic Publishers, Karachi.
Siddiqui, N.K. (2004). Sui Main Limestone: Regional geology and the analysis of original pressures of a closed-system reservoir in central Pakistan. AAPG Bulletin, 88(7), 1007-1035.

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.

Spotted an error? Suggest a sourced correction →

Cite this unit

APA

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

BibTeX

@misc{stratigraphypk_suimainlimestone,
  author    = {Qudsi, Lareb},
  title     = {{Sui Main Limestone 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/sui-main-limestone (accessed October 29, 2026).