Humai Fm
Type Locality and Naming
Holotype section: Koh Humai (proposed). Author: Hunting Survey Corporation, 1960. Reference section: None.
Lithology and Thickness
Sandy limestone. The formation shows great variation in lithology. In Koh Humai, Lower part consists of greenish grey and purple shale, with calcareous sandstone, siltstone, thin-bedded limestone and volcanic conglomerate; and Upper part is massive dense, reefoid limestone. This limestone laterally passes into grey, thick-bedded and sandy limestone in Mazenen Rud. On the eastern flank of the Kacha anticline in the westerly exposures, the formation consists of conglomerate (boulders of limestone and volcanic rock) with gritty and tuffaceous beds and grey, thin bedded limestone. Massive limestone predominates at Kacha Rud, 6 km northeast of Kacha, while purplish grey, some times white, thin to thick bedded limestone predominates at Siah Koh in the easterly exposures.
Thickness: 91-306 m. 91 m at Koh Humai, 306 m in Mazenen Rud.
Relationships and Distribution
Lower contact
Unconformably underlain by Sinjrani Volcanic Gr south of Chagai Hills, elsewhere the contact is disconformable as indicated by basal conglomerate.
Upper contact
Conformably overlain by Rakhshani Fm (Paleocene)
Regional extent
It is restricted to part of the Chagai-Raskoh Magmatic Province (C-RMP, Balochistan Basin) (Eruptive Zone) between the Kacha and Siah Koh areas in North Chagai division.
GeoJSON
Fossils
The formation is fossiliferous and has yielded algae, foraminifers, coelenterates, gastropods and bivalves. Bivalves: Hippurites sp., H. loftusi, Lapeirousia sp., and Monopleuridea gen. Foraminifers: Lepidorbitoides socialis, Orbitella media, Orbitoides sp. Omphalocyclus sp. and aculogypsinoides sp.
Age
Depositional setting
Additional Information