Paleozoic • Carboniferous member GSP memoir

Twin Valley Member

Late Carboniferous (Pennsylvanian)

Karakoram-Hindukush Basin · Central Karakoram Batholith

Part of Lupsuk Formation

Carboniferous in the time scale →

Cited in 4 sources Last reviewed Jul 30, 2026

Unit summary

Rank: member
Status: Published
Age: Paleozoic · Carboniferous · Late CarboniferousLate Carboniferous (Pennsylvanian)
Named by: Gaetani et al. (2004)
Type locality: Twin valleys at the head of the Karambar River
Thickness: 30 to 100 m (sharp lateral thickness variation)
Lithology: Cliff-forming carbonate with sharp lateral facies variations.
Synonyms: Not recorded

The Late Carboniferous carbonate cap of the Lupsuk Formation.

Named by Gaetani et al. (2004) after the Twin Valleys at the head of the Karambar River, the Twin Valley Member is the cliff-forming upper carbonate of the Lupsuk Formation, with sharp lateral facies changes. It overlies a Moscovian brachiopod fauna and is Late Carboniferous in age (Angiolini et al., 1999).

Fossils

Not recorded

Contacts

In the Hindukush-Chitral column

ConglomerateMetamorphicLimestoneFossils recordedUnconformityContact 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: marine
Coordinates: Not recorded

Correlation

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

Economic significance

Not recorded

Remarks

The Late Carboniferous cliff-forming carbonate upper part of the Lupsuk Formation; it overlies a Moscovian brachiopod fauna (Angiolini et al., 1999).

Research notes (4)

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 (4)

CONFIRMED against Zanchi & Gaetani (2011, full text, Fig. 19): the Twin Valleys Member is a 30-100 m bioclastic limestone WITHIN the Lupsuk Formation (~250 m, Karambar sheet), UPPER CARBONIFEROUS (above a Moscovian/Kasimovian fauna; Angiolini et al. 1999). Age/rank conflict confirmed - reconcile the dataset s Devonian-Carboniferous to Upper Carboniferous, member of the Lupsuk Fm (author to confirm).

Zanchi, A. & Gaetani, M. (2011)
Age corrected from "Devonian–Carboniferous" to "Late Carboniferous (Pennsylvanian)" 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 Twin Valleys Member (within the Lupsuk Formation) is inferred Late Carboniferous because it lies above a Moscovian/Kasimovian brachiopod fauna (Angiolini et al. 1999); no macrofossils occur in the member itself. 30–100 m of massive bioclastic limestone (bryozoans, crinoids, brachiopods, corals), capped by terrigenous beds ascribed to the Gircha Formation.

Zanchi, A. & Gaetani, M. (2011)
Gaetani et al. (2004) — DEFINES the Twin Valleys Member, a local bioclastic-limestone intercalation up to ~100 m thick within the Lupsuk Formation (Twin Valleys / Lupsuk Glacier sections), of post-Moscovian (Late Carboniferous / Pennsylvanian) age. Corroborates the curated Late Carboniferous (Pennsylvanian) age; adds the definitional source and confirms the member-of-Lupsuk relationship.

Gaetani, M., Zanchi, A., Angiolini, L., Olivini, G., Sciunnach, D., Brunton, H., Nicora, A. & Mawson, R. (2004)

Sources (3)

Malkani, M.S. & Mahmood, Z. (2017). Stratigraphy of Pakistan. Geological Survey of Pakistan, Memoir Vol. 24.
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.
Gaetani, M., Zanchi, A., Angiolini, L., Olivini, G., Sciunnach, D., Brunton, H., Nicora, A. & Mawson, R. (2004). The Carboniferous of the Western Karakoram (Pakistan). Journal of Asian Earth Sciences, 23(2), 275-305.

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: Appears in a single-author Geological Survey of Pakistan memoir (Malkani & Mahmood 2017), not cross-confirmed against the Shah lexicon. The Stratigraphic Committee of Pakistan is largely inactive, so documented provenance — not formal ratification — is the available signal.

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Cite this unit

APA

Qudsi, L. (2026). Twin Valley Member. In Pakistan Stratigraphy Dataset [Data set]. Zenodo. https://doi.org/10.5281/zenodo.21363991

BibTeX

@misc{stratigraphypk_twinvalleymember,
  author    = {Qudsi, Lareb},
  title     = {{Twin Valley Member} --- 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/twin-valley-member (accessed October 29, 2026).

To cite the unit's original definition instead, see: Gaetani et al. (2004).