Mesozoic • Triassic formation In GSP lexicon

Ailak Formation

Late Permian–Late Triassic

Karakoram-Hindukush Basin · Central Karakoram Batholith

Cited in 9 sources Last reviewed Aug 20, 2026

Unit summary

Rank: formation
Status: Published
Age: Mesozoic · Triassic · Late TriassicLate Permian–Late Triassic
Named by: Gaetani et al. (1995)
Type locality: Baroghil Alak by Gaetani et al36.8500°N, 73.3800°E
Thickness: about 1000 m
Lithology: Massive dolomite and limestone.
Synonyms: Not recorded

A thick Late Permian to Late Triassic dolomite-and-limestone unit of the Baroghil divide.

Named by Gaetani et al. (1995) after Baroghil Alak, the Ailak Formation comprises dolomite and limestone of Late Permian to Late Triassic age in the Karakoram of the upper Hunza–Chitral region.

Fossils

Fusulinid foraminifera (Nankinella, Sphaerulina)Dasyclad alga (Permocalculus)Tubiphytes

Contacts

In the Karakoram column

LimestoneShale / mudFossils 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

Karakoram

Basin: Karakoram-Hindukush Basin
Region: Central Karakoram Batholith
Depositional environment: marine
Coordinates: 36.8500°N, 73.3800°E

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Correlation

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

Economic significance

Not recorded

Remarks

A roughly 1000 m carbonate-platform succession exposed along the continental divide in the Baroghil region, overlying the Gharil Formation; it may be the lateral equivalent of the Kundil and Wirokhun formations of the Chapursan area.

Research notes (9)

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 (7)

Baseline age 'Carboniferous–Paleocene' is a migration/bundling artifact: the Ailak Formation proper is Late Permian to Late Triassic. The baseline description also bundles the Paleocene Misghar Slate and the Pasu Slate, which are separate units and should be split out in Phase-6.

Malkani, M.S. & Mahmood, Z. (2017)
Spans Late Permian to Late Triassic (Malkani, 2017); most of the unit is Triassic, so the era badge is set to Mesozoic (period Triassic) with the full range kept in the age line. A boundary-convention call. (Separately, the baseline description appears to bundle the Paleocene Misghar and Pasu slates, which are distinct units to split out in a later pass.)

Malkani, M.S. & Mahmood, Z. (2017)
CONFIRMED against Zanchi & Gaetani (2011, Fig. 19): the Ailak Formation is Triassic, 0->150 m (Lasht/Siru) to 500-600 m (Lashkargaz/Baroghil). Consistent with the dataset's Late Permian-Late Triassic span.

Zanchi, A. & Gaetani, M. (2011)
Gaetani et al. (2013): in the Baroghil (Lashkargaz–Baroghil) platform succession the Ailak Formation is a ~500–600 m peritidal dolostone unit whose lower grey part is Late Permian (fusulinids Nankinella and Sphaerulina with the dasyclad alga Permocalculus; Leven et al. 2007) and whose upper whitish stromatolitic part is Triassic (about 40–50% of the unit), consistent with the curated Late Permian–Late Triassic span. Deep karst infillings (up to ~100 m) with volcanic/metamorphic quartz mark platform emersion, possibly Cimmerian peripheral-bulge uplift.

Gaetani, M., Nicora, A., Henderson, C., Cirilli, S., Gale, L., Rettori, R., Vuolo, I. & Atudorei, V. (2013)
Zanchi & Gaetani (2011): the type section of the Ailak Formation is the ridge of the continental divide between the Baroghil and Darwaz passes (introduced by Gaetani et al. 1996); >550 m of peritidal dolostone whose lower grey part is Late Permian (fusulinids Nankinella and Sphaerulina, Tubiphytes, Permocalculus) and whose lighter upper part is Triassic — the dolostone contains the Permian/Triassic boundary, with internal gaps in the Triassic part. Huge palaeokarst cavities (up to 100 m deep) at the Baroghil Pass record Cimmerian-age emersion; transgressively overlain by the Lower Jurassic Darwaz An Formation.

Zanchi, A. & Gaetani, M. (2011)
Perri, Molloy & Talent (2004): the Ailak Dolomite (name introduced by Gaetani et al. 1995; the DB 'Ailak Formation') is a ~1,000+ m sequence of dolostones up the Yarkhun valley, extending eastwards; it carries a diverse Late Permian foraminifer fauna in dark grey thick-bedded limestones ~460 m above the base and, towards the top, foraminifer 'ghosts' suggestive of a Late Triassic attribution — i.e. Late Permian to ?Late Triassic, matching the curated age. It passes eastwards into slope and offshore facies in the Chapursan and Shimshal valleys of upper Hunza and forms the type of the 'Ailak–Zait Carbonate Platform'. Corroborates the curated Late Permian–Late Triassic age and ~1,000 m thickness.

Perri, M.C., Molloy, P.D. & Talent, J.A. (2004)
Gaetani et al. (1995): the Ailak Formation (>1,000 m of massive dolostones capping the western succession from Baroghil to Chillinji, correlated with the Guhjal Dolomite of Hunza) yielded no age-diagnostic fossils and is bracketed only on stratigraphic position between the Kubergandian and ?Midian; its Murgabian-Midian dolostone transgression is correlated across the Pamirs, Central Afghanistan and the Tethys Himalaya as a turning point in the initial opening of Neo-Tethys. A huge paleokarst (solution cavities up to ~100 m deep) at the Chitral/Wakhan boundary records emersions placed in the Mesozoic, consistent with the unit's Late Permian-Late Triassic span.

Gaetani, M., Angiolini, L., Garzanti, E., Jadoul, F., Leven, E.Ya., Nicora, A. & Sciunnach, D. (1995)

Fossils & biostratigraphy (1)

Surfaced from the age notes into fossils[]: the lower grey (Late Permian) part of the Ailak dolostone yields fusulinids Nankinella and Sphaerulina with the dasyclad alga Permocalculus and Tubiphytes (Zanchi & Gaetani 2011; Gaetani et al. 2013, after Leven et al. 2007). These fix the Permian/Triassic boundary within the unit.

Zanchi, A. & Gaetani, M. (2011)

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.
OpenStreetMap contributors and GEOnet Names Server (public geographic gazetteers), used to geolocate named GSP type localities to approximate decimal coordinates.
Zanchi, A. & Gaetani, M. (2011). The geology of the Karakoram range, Pakistan: the new 1:100,000 geological map of Central-Western Karakoram. Italian Journal of Geosciences, 130(2), 161-262.
Shah, S.M.I. (2009). Stratigraphy of Pakistan. Geological Survey of Pakistan, Memoir Vol. 22.
Gaetani, M., Nicora, A., Henderson, C., Cirilli, S., Gale, L., Rettori, R., Vuolo, I. & Atudorei, V. (2013). Refinements in the Upper Permian to Lower Jurassic stratigraphy of Karakorum, Pakistan. Facies, 59, 915-948.
Perri, M.C., Molloy, P.D. & Talent, J.A. (2004). Earliest Triassic conodonts from Chitral, northernmost Pakistan. Rivista Italiana di Paleontologia e Stratigrafia, 110(1), 467-478.
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.
Gaetani, M., Angiolini, L., Garzanti, E., Jadoul, F., Leven, E.Ya., Nicora, A. & Sciunnach, D. (1995). Permian stratigraphy in the Northern Karakorum, Pakistan. Rivista Italiana di Paleontologia e Stratigrafia, 101(2), 107-152.

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

BibTeX

@misc{stratigraphypk_ailakformation,
  author    = {Qudsi, Lareb},
  title     = {{Ailak 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/ailak-formation (accessed October 29, 2026).

To cite the unit's original definition instead, see: Gaetani et al. (1995).

Below · older

Gharil Formation

Permian

Referenced in other successions

Overlain by Darwaz An Formation

Underlain by Ini Sar Formation