Toi Fm
Type Locality and Naming
Ghazij Gr – second formation in portions of Sulaiman Province (SP). Holotype section: Moghal Kot section - (also known as Toi Nallah). Author: S. M. Hussain, 1977 (verbal communication, as in Shah, 2009). Reference section: None.
Lithology and Thickness
Sandstone. In the type section, the formation comprises of dark brown to red brown, olive green to light grey green sandstone. The sandstone in this area is medium to coarse grained, poorly sorted, laminated and cross-bedded. It is interbedded with siltstone, claystone, shale and conglomerate. The formation comprises sandstone, siltstone, conglomerate, silty claystone and shales with locally developed coal seams. The sandstone is mostly coarse grained, pebbly, poorly sorted and conspicuously cross-bedded. The siltstone is dark chocolate brown to red brown in color, soft, blocky, argillaceous that commonly grades into sandstone or shale. The conglomerate is dark brown, and contains poorly sorted, subangular to subrounded pebbles and boulders of sandstone and limestone cemented in ferruginous and argillaceous sandstone matrix. The shales are grey green to slightly micaceous dark grey, fissile and occasionally carbonaceous. Top of the formation in type section is composed of blocky sandstone interbedded with conglomerate calcirudite. In the Sore Range near Quetta, the formation consists of calcareous sandstone, conglomerate, calcareous claystone and carbonaceous shale, with commercially exploitable coal seams. Towards the southeast, the sandstone and conglomerate grade into beds of limestone. The conglomerate beds are up to
6 m thick and are remarkably continuous. The pebbles in the conglomerate include chert and limestone derived from older formations of the Axial Belt.
Thickness: An abrupt and maximum thickness of 2,120 m encountered in the type section. At the type section, it is 2,120 m thick, whereas it is missing in Zindapir area.
Relationships and Distribution
Lower contact
Upper contact
Conformably underlain by Shaheed Ghat Fm
Regional extent
The formation is rather a facies change of the Shaheed Ghat Fm at the extreme ends of its outcrop region. The exposures of Toi Fm are located north of 31st parallel in the Sulaiman Range, and then at extreme southwest in Sore Range near Quetta. It is not present in the Drug Tangi section but abruptly appears in the Moghal Kot section (in Toi Nallah). Maximum thickness of 2,120 m of this formation is encountered in this nallah, hence the name.
GeoJSON
Fossils
Poorly fossiliferous. Some pelecypod and gastropod fossils were collected from coal bearing horizons near Quetta.
Age
Depositional setting
Predominantly composed of fluviatile and estuarine sediments.
Additional Information
EMW: Coal.