Paleozoic • Ordovician formation In GSP lexicon

Yarkhun Formation

Ordovician (Early Ordovician)

Karakoram-Hindukush Basin · Central Karakoram Batholith

Part of Baroghil Group

Ordovician in the time scale →

Cited in 7 sources Last reviewed Jul 31, 2026

Unit summary

Rank: formation
Status: Published
Age: Paleozoic · Ordovician · Early OrdovicianOrdovician (Early Ordovician)
Named by: Gaetani et al. (1996)
Type locality: Type section on the SE side of the Vidiakot ridge (Quintavalle et al., 2000), between the Yarkhun River and the Vidiakot gully, Axial Unit; rests with basal non-conformity on the Karakoram crystalline basement (Ishkarwaz-type granodiorite).
Thickness: about 170 m
Lithology: About 170 m of arkosic sandstone interbedded with siltstone and black slate.
Synonyms: Not recorded

A Silurian sandstone–siltstone–slate unit of the upper Yarkhun valley.

Yarkhun formation consists of 170m arkosic sandstone interbedded with siltstone and black slate. It is Silurian age.

Fossils

Conodonts (Baltoniodus cf. medius)Acritarchs Trace fossils (Cruziana, Planolites)

Contacts

In the Hindukush-Chitral column

MetamorphicMixedSandstoneShale / 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

Hindukush-Chitral

Basin: Karakoram-Hindukush Basin
Region: Central Karakoram Batholith
Depositional environment: shallow marine, siliciclastic shelf
Coordinates: Not recorded

Correlation

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

Economic significance

Not recorded

Remarks

A Silurian siliciclastic unit of the lower Paleozoic succession of the upper Yarkhun (Hindukush) region.

Research notes (8)

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 (5)

Age corrected from "Silurian" to "Ordovician (Early Ordovician)" per Zanchi & Gaetani (2011, Fig. 19, North Karakoram Terrain correlation chart); author-approved 2026-07-17.

Zanchi, A. & Gaetani, M. (2011)
Zanchi & Gaetani (2011): the Yarkhun Formation (lower unit of the Baroghil Group) is restricted to the Arenig (Early Ordovician) — acritarch assemblages VK1–VK2 and conodonts (Baltoniodus sp. cf. B. medius) span the nitidus to hirundo graptolite zones, with an overlying conodont level reaching the latest Arenig–lower Llanvirn. About 180 m of grey subarkoses/litharenites with Cruziana and Planolites, recording transgression on a peneplaned crystalline basement.

Zanchi, A. & Gaetani, M. (2011)
Kazmi & Jan (1997): the Yarkhun Formation appears (after Tahirkheli 1982) as flaggy quartzites, slates and thin dolomitic limestones in the upper Yarkhun Valley (south of Baroghil Pass), intruded by the pre-Ordovician Ishkarwaz Granite and overlain across an angular unconformity by a dolomitic bed with Ordovician conodonts — implying a pre-Ordovician basement age here; the running text proposes the name 'Chikar Formation' for the same sequence (Le Fort et al. 1994). (The curated Arenig/Early-Ordovician age follows the later Zanchi & Gaetani 2011 definition, which is retained.)

Kazmi, A.H. & Jan, M.Q. (1997)
Talent, Gaetani, Mawson, Molloy & Conaghan (1999), 'Early Ordovician and Devonian conodonts [from the Karakoram Terrane], northernmost Pakistan' (RIPS) — the primary conodont study underpinning the Early Ordovician age of the Yarkhun Formation, cited by Perri et al. (2004) for the NE-Chitral stratigraphy. NOTE: the supplied PDF of this 1999 paper is a scanned image with no text layer and could not be machine-read in this environment (no OCR), so only its title-level content (Early Ordovician conodonts, Karakoram Terrane) is used here to corroborate the curated Early Ordovician age; its detailed zonation is not yet incorporated and the paper is flagged for re-supply as a text-layer PDF.

Talent, J.A., Gaetani, M., Mawson, R., Molloy, P.D. & Conaghan, P.J. (1999)
Talent et al. (1999) — FULL TEXT (supersedes the earlier title-level note): the Yarkhun Formation includes Early Ordovician (Arenig) horizons, confirmed both by acritarch floras (late-early Arenig nitidus/gibberulus Graptolite Zone to late Arenig hirundo Zone; Amerise et al. 1998, from the Vidiakot section) and by a small Ordovician conodont fauna (2.5 km WNW of the Ishkarwaz bridge, upper Yarkhun valley). Importantly, this paper INTRODUCES the Vidiakot Formation for the upper, finer-grained part of the former Yarkhun Formation and RESTRICTS the Yarkhun Formation to the stratigraphically lower, coarser (terrigenous) part; together with the overlying Chilmarabad Formation these three correspond to Tahirkheli's (1982, 1996) Baroghil Formation and perhaps warrant group status (the dataset's Baroghil Group). Corroborates the curated Early Ordovician (Arenig) age.

Talent, J.A., Gaetani, M., Mawson, R., Molloy, P.D. & Conaghan, P.J. (1999)

Lithology (1)

CONFIRMED against Zanchi & Gaetani (2011, full text, Fig. 19): the Yarkhun Formation (~170 m) is the basal unit of the Baroghil Group and sits at the LOWER ORDOVICIAN level of the North Karakoram Terrain correlation chart. The dataset lists Silurian — this should be corrected to (Lower) Ordovician (author to confirm).

Gaetani, M., Le Fort, P., Tanoli, S., Angiolini, L., Nicora, A., Sciunnach, D. & Khan, A. (1996)

Fossils & biostratigraphy (1)

Surfaced from the age notes into fossils[]: the Yarkhun Formation carries Early Ordovician (Arenig) conodonts (Baltoniodus sp. cf. B. medius) and acritarch assemblages VK1–VK2 (Zanchi & Gaetani 2011; Talent et al. 1999, after Amerise et al. 1998). Cruziana and Planolites are kept explicitly labelled as trace fossils (ichnofossils), not body fossils.

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

Sources (9)

Malkani, M.S. & Mahmood, Z. (2017). Stratigraphy of Pakistan. Geological Survey of Pakistan, Memoir Vol. 24.
Gaetani, M. and others (1996). Reconnaissance geology in Upper Chitral, Baroghil and Karambar districts (northern Karakorum, Pakistan). Geologische Rundschau, 85, 683-704.
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.
Kazmi, A.H. & Jan, M.Q. (1997). Geology and Tectonics of Pakistan. Graphic Publishers, Karachi.
Talent, J.A., Gaetani, M., Mawson, R., Molloy, P.D. & Conaghan, P.J. (1999). Early Ordovician and Devonian conodonts from the Karakoram Terrane, northernmost Pakistan. Rivista Italiana di Paleontologia e Stratigrafia (1999).
Talent, J.A., Gaetani, M., Mawson, R., Molloy, P.D. & Conaghan, P.J. (1999). Early Ordovician and Devonian conodonts from the Western Karakoram and Hindu Kush, northernmost Pakistan. Rivista Italiana di Paleontologia e Stratigrafia, 105(2), 201-226.
Gaetani, M., Le Fort, P., Tanoli, S., Angiolini, L., Nicora, A., Sciunnach, D. & Khan, A. (1996). Reconnaissance geology in Upper Chitral, Baroghil and Karambar districts (northern Karakorum, Pakistan). Geologische Rundschau, 85, 683-704.
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.

Reviewer confidence: medium

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

BibTeX

@misc{stratigraphypk_yarkhunformation,
  author    = {Qudsi, Lareb},
  title     = {{Yarkhun 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/yarkhun-formation (accessed October 29, 2026).

To cite the unit's original definition instead, see: Gaetani et al. (1996).

Above · younger

Vidiakot Formation

Ordovician