Cenozoic • Quaternary formation In GSP lexicon

Bostan Formation

Middle Pleistocene to present (Chibanian-Holocene; ~0.77-0 Ma)

Balochistan Basin · Kakar-Khurasan Basin

Cited in 8 sources Last reviewed Aug 2, 2026

Unit summary

Rank: formation
Status: Published
Age: Cenozoic · Quaternary · Middle Pleistocene to HoloceneMiddle Pleistocene to present (Chibanian-Holocene; ~0.77-0 Ma)
Named by: Malkani (2012)
Type locality: Kamroud village, Siahan Range (Makran)30.4325°N, 67.0061°E
Thickness: 600-750 m
Lithology: Gypsiferous claystone to sandstone; lacustrine to playa deposits.
Synonyms: Sakhi Sarwar Group (in part)

A very young (Pleistocene–Holocene) gravel-and-mud molasse of northern Balochistan.

The Bostan Formation is named after the village of Bostan, 20 km east of Kuchlak (HSC 1961). It consists of clay, silt, sandstone and conglomerate; the clay and silt are red to maroon and brown, and the sandstone and conglomerate are medium to thick bedded and mostly friable, indicating uplift of the area. It is assigned to the Pleistocene-Holocene Sakhi Sarwar Group (Malkani 2012k, 2014c) - first used after the Sakhi Sarwar area of D.G. Khan and treated as synonymous with the Bostan Formation - which comprises the Dada Formation (mainly conglomerate) and the Sakhi Sarwar Formation (mud and sandstone with poorly developed conglomerate, mud-dominant in valley centres), concealed at places in valleys and plains by Subrecent and Recent fluvial, eolian and colluvial deposits.

Fossils

Not recorded

Contacts

In the Zhob-Muslim Bagh column

Shale / mudConglomerateConformable

Band colour = period; texture = dominant rock type. Lines between bands mark the contact type. 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

Zhob-Muslim Bagh

Basin: Balochistan Basin
Region: Kakar-Khurasan Basin
Depositional environment: lacustrine, playa
Coordinates: 30.4325°N, 67.0061°E

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Correlation

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

Economic significance

Not recorded

Remarks

A Pleistocene–Holocene molasse of the Kakar-Khurasan/Pishin region, equivalent to the Sakhi Sarwar Group (Boston Formation), capping the basin fill.

Research notes (7)

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 as 'Bostan formation'). Adds the definitional GSP/SCP lexicon citation.

Shah, S.M.I. (2009)

Age & correlation (1)

Kazmi & Jan (1997): the Bostan Formation (believed Pleistocene; type sections Pishin Lora and Kamerod village) is folded lacustrine-to-playa gypsiferous white/grey/brick-red clay interbedded with salt-and-pepper thin sandstone and conglomerate, laid down in tectonic depressions and unconformably overlying the Neogene and older rocks (transitional with the Khojak Formation in the Dalbandin Valley); unfossiliferous.

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

Lithology (2)

Revised to gypsiferous claystone-sandstone of lacustrine-playa origin per the Indian Plate Lexicon (compiler N.K. Siddiqui), superseding a 'foreland molasse conglomerate' description.

Indian Plate Lexicon (indplex.geolex.org), Geological Society of India and international compilation.
Corroborated by USGS OFR 94-689: Pleistocene lacustrine clay (gypsiferous), conglomerate and salt-and-pepper sandstone; unconformable on older strata; ~750 m thick in the Pishin Basin (Cheema et al. 1977).

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

Type locality & location (1)

Type locality specified as Kamroud village, Siahan Range (Makran), superseding 'Village Bostan'.

Indian Plate Lexicon (indplex.geolex.org), Geological Society of India and international compilation.

Stratigraphic contacts (1)

Lower contact: unconformably overlies the Shirinab, Loralai, Nisai and Khojak formations; conformably overlies the Haro Conglomerate in the Axial Belt. Upper contact is the present surface.

Indian Plate Lexicon (indplex.geolex.org), Geological Society of India and international compilation.

Geological significance (1)

Kasi et al. (2012): in the Pishin Belt the name Bostan Formation (Hunting Survey Corporation 1960) denotes a Pleistocene red-bed molasse — red shale/siltstone with conglomerate and sandstone — forming Zone V, thrust over the Malthanai Formation and in turn overthrust by the Holocene Zhob valley deposits. This Pishin-Belt usage should be reconciled with the curated Makran (Siahan Range) attribution of the record.

Kasi, A.K., Kassi, A.M., Umar, M., Manan, R.A. & Kakar, M.I. (2012)

Sources (8)

Malkani, M.S. & Mahmood, Z. (2017). Stratigraphy of Pakistan. Geological Survey of Pakistan, Memoir Vol. 24.
OpenStreetMap contributors and GEOnet Names Server (public geographic gazetteers), used to geolocate named GSP type localities to approximate decimal coordinates.
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.
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.
Kasi, A.K., Kassi, A.M., Umar, M., Manan, R.A. & Kakar, M.I. (2012). Revised lithostratigraphy of the Pishin Belt, northwestern Pakistan. Journal of Himalayan Earth Sciences, 45(1), 53-65.

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

BibTeX

@misc{stratigraphypk_bostanformation,
  author    = {Qudsi, Lareb},
  title     = {{Bostan 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/bostan-formation (accessed October 7, 2026).

To cite the unit's original definition instead, see: Malkani (2012).

Referenced in other successions

Underlain by Haro Conglomerate Formation· Malthanai Formation