Mesozoic • Cretaceous

Sembar Formation

Early Cretaceous (Berriasian-Barremian)

Stratigraphic position

In the Sulaiman Fold Belt column

Shale / mudSandstoneLimestoneFossils 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 black shale — the main source rock that generated the gas in Pakistan's Indus Basin fields.

Major source rock for hydrocarbons in Indus Basin. Deposited in anoxic marine conditions. Equivalent to Chichali in upper Indus.

Significance. An Early Cretaceous organic-rich marine shale that is the main petroleum source rock of the Indus Basin, deposited during Gondwana rifting as the Indian plate began to separate.

Lithology: Black, carbonaceous, pyritic shale with subordinate siltstone, sandstone and thin limestone; thins westward.
Thickness: 100-300 m
Type locality: Sembar Pass, Sulaiman Range
Environment: marine, outer shelf
Economic importance: The principal hydrocarbon SOURCE ROCK of the Lower and Central Indus Basin (Sui, Mari and other gas fields); the Sembar–Lower Goru is an active petroleum system.

Fossils

AmmonitesBelemnitesForaminifera

Provinces

Sulaiman Fold Belt Kirthar Range Sindh Province

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.
Iqbal, M. et al. (2017). Hydrocarbon exploration perspective in Middle Jurassic-Early Cretaceous reservoirs in the Sulaiman Foldbelt, Pakistan. (ResearchGate).

Reviewer confidence: high

Related units

Above · younger

Goru Formation

Cretaceous