Pirkoh Fm

Ghazij Gr – seventh formation in Sulaiman Province (SP). Holotype section: Pirkoh Anticline- provisional. Hypo: Dhurwali Chur. Author: F.E. Eames, 1952.

Reference section: Lithologically same as in the type section but with much reduced thickness of 10-15m.

Limestone. It consists of limestone that is light grey to chalky white, buff to brown, fine-grained, mostly thin and regularly bedded, and often argillaceous. The formation commonly contains subordinate beds of soft, shaly limestone and dark grey calcareous claystone. It also shows presence of oil shale. The limestone forms persistent and continuous ridges throughout eastern Sulaiman Range and Marri-Bugti area, which can be traced easily on the satellite imagery. At the proposed type locality, the core of the Pirkoh structure is completely covered by the limestone of this formation.

Thickness: 10-100 m. At the type section, it is 135 m thick. However, in the northeast it thins out drastically along the eastern Sulaiman Range, where the thickness ranges between 10-15 m. South of the type locality, its thickness in subsurface is over 100 m at Sui gasfield; farther south in subsurface its thickness is of the same order in Kandhkot, Qadirpur and Mari gasfields.

Three larger foraminiferal assemblage zones in Thak section (Eastern Salt Range) are recognized. Assilina spira abrardi at the base, Discocyclina dispansa and D. sowerbyi in the middle and Nummulites sp. A. zone on the top (Afzal et al., 1997 as in Kazmi and Abbasi, 2008).

It was probably deposited under calm shelf conditions without much of clastic influx.

Age span:

Beginning stage: Lutetian

Fraction up in beginning stage: 0.75

Beginning date (Ma):

Ending stage: Bartonian

Fraction up in ending stage: 0.5

Ending date (Ma):

Depositional setting: