Isha Formation
Middle to Late Jurassic (Bathonian-Kimmeridgian; ~168.17-149.24 Ma)
Jurassic in the time scale →Cited in 3 sources Last reviewed Jul 18, 2026
- Rank
- formation
- Status
- Published
- Age
- Mesozoic · Jurassic · Middle to Late JurassicMiddle to Late Jurassic (Bathonian-Kimmeridgian; ~168.17-149.24 Ma)
- Named by
- Ahmad et al. (2000)
- Type locality
- Isha Check Post, North Waziristan
- Thickness
- 100 m at the type locality. m
- Lithology
- The formation typically consists of thick bedded to massive limestone with minor shale intercalations. Limestone. At the type locality, the limestone is mostly dark grey to blue in color, and weathers to light grey and to brownish colors. At places, the limestone is thin to thick bedded, hard and contains some secondary calcite veins, chert nodules, ooides, pisolite and pellets. Its texture varie…
- Synonyms
- Not recorded
The formation typically consists of thick bedded to massive limestone with minor shale intercalations. Limestone. At the type locality, the limestone is mostly dark grey to blue in color, and weathers to light grey and to brownish colors. At places, the limestone is thin to thick bedded, hard and contains some secondary calcite veins, chert nodules, ooides, pisolite and pellets. Its texture varies from fine grained, sublithographic to oolitic, reefoid and shelly. In the upper part, the limestone is fairly jointed, fractured and calcite veins are present in these openings. The limestone forms …
Fossils
Not recorded
Contacts
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
- Basin
- Not recorded
- Region
- Not recorded
- Depositional environment
- Not recorded
- Coordinates
- Not recorded
Correlation
Not recorded. Compare this unit against other basins on the correlation panel →
Economic significance
Not recorded
Remarks
Not recorded
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.
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 (1)
Stratigraphic contacts (1)
-
Ahmad et al. (2000): the Isha Formation (limestone) grades up from the Sarobi Formation (gradational lower contact) and is DISCONFORMABLY overlain by the Cretaceous Chashmai Kharsai Formation. Name introduced herein after the Isha check post.
Distribution (1)
-
Province corrected from zhob-muslim-bagh to sulaiman: Ahmad et al. (2000) place this unit in NORTH WAZIRISTAN (Mirali-Miran Shah-Razmak), part of the western Axial/Sulaiman belt - not the Zhob-Muslimbagh area. (A dedicated Waziristan province could be added later.)
Sources (3)
- Indian Plate Lexicon (indplex.geolex.org), Geological Society of India and international compilation.
- Ahmad, S., Ali, F., Rehman, N. & Gul, J. (2000). Lithostratigraphy of the Kurram Group along the Mirali-Miran Shah Road, North Waziristan Agency, NWFP, Pakistan. Geological Bulletin, University of Peshawar, 33, 79-86.
- Shah, S.M.I. (2009). Stratigraphy of Pakistan. Geological Survey of Pakistan, Memoir Vol. 22.
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.
Cite this unit
Qudsi, L. (2026). Isha Formation. In Pakistan Stratigraphy Dataset [Data set]. Zenodo. https://doi.org/10.5281/zenodo.21363991
@misc{stratigraphypk_ishaformation,
author = {Qudsi, Lareb},
title = {{Isha 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/isha-formation (accessed October 29, 2026).
To cite the unit's original definition instead, see: Ahmad et al. (2000).
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