Mesozoic • Jurassic formation

Dilband Formation

Jurassic

Kirthar Basin · Western Kirthar (Balochistan)

Stratigraphic position

In the Kirthar Range column

SandstoneMixedShale / mudLimestoneFossils recordedConformable

Band colour = period; texture = dominant rock type. Lines between bands mark the contact type. 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.

An Early Cretaceous ironstone unit in Kalat District — the home of Pakistan's biggest iron-ore deposit.

Dilband Formation Dilband Formation which is about 20m thick in the type area (northern Kirthar range) was named by Abbas et al. (1998) and designated three members like lower Jarositic clay member (light grey to brown), middle ironstone member (reddish), and upper green glauconitic shale member. The Dilband Formation (synonym Mazar Drik Formation) is less than 30 m and exposed also in the Dilband Johan-Moola Zahri Range of Kirthan foldbelt and Loralai, Duki and Gadebar areas of Sulaiman foldbelt. It includes mostly the transitional and disconfirmable horizons representing Jurassic Cretaceous (J-K) boundary. This J-K boundary exposed in Duki, Loralai, Daman Ghar and Gadebar areas is represented by light brown shale alternated with light grey fresh colour and light brown weathered colour limestone belong to Dilband Formation. Its lower contact with Chiltan (Takatu/Zidi) Limestone and upper contact with Sembar Formation is disconfirmable and at places conformable. Ammonits from Mazar Drik and Moro area include Macrocephalites, Dolikephalites, Indocephalites, Pleurocephalites, Indosphinctes and Choffatia (Fatmi 1977). Arkell (1956) reported Bullatimorphites bullatus and Clydoniceras from the lower part of Mazar Drik unit/Dilband Formation, representing Late Bathonian age. Recently Malkani (2003c) has found dinosaurs ( Brohisaurus kirthari ) fossils from Sun Chaku (Karkh

Significance. An Early Cretaceous ironstone-bearing unit resting on the top-Chiltan unconformity in the Kalat region, the host of Pakistan's principal iron-ore resource.

Lithology: Oolitic hematite ironstone with sandstone and shale.
Thickness: about 20m
Type locality: Dilband area, Kalat District
Basin: Kirthar Basin
Region: Western Kirthar (Balochistan)
Environment: shallow marine
Introduced by: Abbas et al. (1998)
Economic importance: Hosts the Dilband iron-ore deposit — Pakistan's largest — oolitic hematite at the top-Chiltan unconformity grading about 52–62% iron oxide.

Fossils

ChoffatiaBullatimorphites bullatusClydonicerasBrohisaurus kirthari

Provinces

Kirthar Range

References

Malkani, M.S. & Mahmood, Z. (2017). Stratigraphy of Pakistan. Geological Survey of Pakistan, Memoir Vol. 24.
Kazmi, A.H. & Jan, M.Q. (1997). Geology and Tectonics of Pakistan. Graphic Publishers, Karachi.

Reviewer confidence: high

Related units

Above · younger

Sembar Formation

Cretaceous