Lumshiwal Fm
Type Locality and Naming
Surghar Gr – upper formation: Holotype section: one km north of Lumshiwal Nallah, SuR. Hypo: Because of considerable variation in lithology and thickness, three reference sections namely, Fort Lockhart Road section in Samana Range, Wuch Khwar section near Nizampur and Jhamiri village section on Haripur- Jhabrian Road section in Hazara have been designated. Author: E.R. Gee, 1945.
Lithology and Thickness
Sandstone. In the type locality and other sections of Trans Indus Range (TrIR) the lithology consists of thick bedded to massive, light grey current bedded sandstone with silty, sandy, glauconitic shale towards the base. The sandstone is feldspathic, ferruginous and contains carbonaceous material in the upper part. In TrIR it is generally unfossiliferous and mostly of continental origin.
Reference section: In Samana Range, the lower part consists of fine to medium grained, thin to medium bedded, light grey, brown, quartzose sandstone. The middle part is massive, thick bedded, cliff forming, coarse to medium grained, light grey sandstone. In the upper part, sandstone is ferruginous and glauconitic with some sandy limestone that contains abundant fossil casts. In Nizampur, eastern Kohat, KcR and southern Hazara the lithology consists of quartzose, glauconitic and calcareous sandstone in the lower part, followed by a sequence of greenish-to-greenish grey, silty, thin to medium bedded sandstone, overlain by thin to medium bedded, argillaceous limestone. In Jhamiri village section and adjacent areas, the formation is a quartzose, ferruginous sandstone, weathering yellowish brown with locally calcareous sandy beds and a hard calcareous sandstone or sandy limestone bed at the top with abundant fossils.
Thickness: 47-194 m. Thickness varies from 80 to 120 m in the Lumshiwal Nallah and 38 m in the Chichali Pass section. In the western Kohat (Samana Range), it is 194 m thick, but thins out further east in Wuch Khwar section to 47 m. In Kalachitta Range, it is 50-60 m. At Haripur-Jhabrian Road section, it is 50 m thick.
Relationships and Distribution
Lower contact
Conformably underlain by Chichali Fm (transitional).
Upper contact
Disconformably overlain by Kawagarh Fm in Kohat and Hazara areas. In southern Potwar and TrIR it is overlain by Tertiary formations and no upper Cretaceous rock are developed.
Regional extent
The formation is widely distributed particularly in TrIR and Kohat area. On western side, it occurs from Samana Range in the north to TrIR in the south. Towards east in the Western Salt Range the formation thins out and disappears.
GeoJSON
Fossils
Generally unfossiliferous. Gryphea sp., Hibolithes sp., Douvilleiceras mammillatum, Oxytropidoceras spp., Desmoceras sp., Cleoniceras sp. Brancoceras sp. and Lemunoceras sp. are reported.
Age
Depositional setting
In TrIR it is mostly unfossiliferous and of continental origin, but elsewhere it is marine.
Additional Information
EMW: Oil & gas in Kohat area (western Ko-MP).