Mesozoic • Triassic-Jurassic group In GSP lexicon

Shirinab Formation

Early Jurassic (Pre-Toarcian). Keeping in view the enormous thickness of the formation, it is believed that it may extend into the Triassic (Rhaetian-Pliensbachian; ~203.55-184.2 Ma)

Triassic-Jurassic in the time scale →

Cited in 7 sources Last reviewed Aug 2, 2026

Unit summary

Rank: group
Status: Published
Age: Mesozoic · Triassic-Jurassic · Early Jurassic (Pre-Toarcian); maybe into late TriassicEarly Jurassic (Pre-Toarcian). Keeping in view the enormous thickness of the formation, it is believed that it may extend into the Triassic (Rhaetian-Pliensbachian; ~203.55-184.2 Ma)
Named by: Hunting Survey Corporation (1960)
Type locality: Shirinab River section
Thickness: 230- >1,000 m More than 1,000 m in the Kallat section, and 230 m (measured, base not exposed) in the Gurruk-Ziarat section. m
Lithology: Limestone. In the type area, the formation consists of limestone with subordinate marl and shale. The limestone is thin- to thick-bedded, grey to dark grey, ash grey, weathers rusty brown to brownish grey, mottled, sub-lithographic, micritic to biomicritic with shelly, oolitic, peletic and pisolitic interbeds. It is also crinoidal, platy, flaggy, dolomitized and argillaceous at places. Coquina be…
Synonyms: Not recorded

Nomenclature

Formal name · in current use. First defined by Hunting Survey Corporation (1960).

Supersedes Loralai Formation.

Browse all alternative & superseded names →

Limestone. In the type area, the formation consists of limestone with subordinate marl and shale. The limestone is thin- to thick-bedded, grey to dark grey, ash grey, weathers rusty brown to brownish grey, mottled, sub-lithographic, micritic to biomicritic with shelly, oolitic, peletic and pisolitic interbeds. It is also crinoidal, platy, flaggy, dolomitized and argillaceous at places. Coquina beds are common. The marl is greenish grey and nodular. The shale dominates the upper part and is buff, maroon, greenish grey to brown, calcareous, and ranges from soft flaky to hard fissile. The format…

Fossils

Lower Toarcian ammonites (Bouleiceras, Protogrammoceras); brachiopods, corals

Contacts

In the Zhob-Muslim Bagh column

LimestoneFossils 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.

Constituent units

Formations that make up this group, in stratigraphic order (youngest at top, as in the column).

Distribution & setting

Zhob-Muslim Bagh

Basin: Not recorded
Region: Not recorded
Depositional environment: marine, shallow marine
Coordinates: Not recorded

Correlation

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

Economic significance

Source rock

Dark Loralai and Anjira members indicate source-rock richness (need TOC/maturity testing).

Remarks

The Early–Middle Jurassic deep-to-shallow carbonate-platform succession of the Sulaiman–Kirthar belt (with the Spingwar, Loralai and Anjira members), deposited on the northwestern passive margin of the Indian Plate within the Palaeo-Tethys and passing upward into the shallower Chiltan Limestone.

Research notes (2)

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 & Jan (1997): the Shirinab Formation (as presently recognised Early Jurassic/Lower Jurassic; 1,500–3,000 m of interbedded limestone and shale in Kalat/Quetta/Zhob/Loralai) is subdivided into the Spingwar (Liassic, ammonite-dated, type at Spingwar), Loralai and Anjira Members (Williams 1959); it grades down into the Triassic Wulgai Formation and up into the Middle Jurassic Takatu Limestone. The original HSC (1960) 'Shirinab Formation' lumped undifferentiated Jurassic-Triassic-Permian rocks; near Khuzdar it was renamed the Ferozabad Group.

Kazmi, A.H. & Jan, M.Q. (1997)

Depositional environment (1)

Gap-fill (environment field was empty). USGS OFR 94-689 describes the Shirinab Formation as thin- to medium-bedded limestone (fine to coarse grained, shelly, oolitic, pisolitic, pelitic) interbedded with calcareous fissile shale, >1,500 m thick in the Quetta Valley (Khan et al. 1986) — a shallow-marine shelf-carbonate succession.

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

Sources (7)

Indian Plate Lexicon (indplex.geolex.org), Geological Society of India and international compilation.
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.
Shah, S.M.I. (2009). Stratigraphy of Pakistan. Geological Survey of Pakistan, Memoir Vol. 22.
Kadri, I.B. (1995). Petroleum Geology of Pakistan. Pakistan Petroleum Limited, Karachi.
Kazmi, A.H. & Jan, M.Q. (1997). Geology and Tectonics of Pakistan. Graphic Publishers, Karachi.
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.

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

BibTeX

@misc{stratigraphypk_shirinabgroup,
  author    = {Qudsi, Lareb},
  title     = {{Shirinab 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/shirinab-group (accessed October 29, 2026).

To cite the unit's original definition instead, see: Hunting Survey Corporation (1960).

Below · older

Malikhore Formation

Jurassic

Above · younger

Chiltan Limestone