Distribution of Precambrian - Cambrian Succession Along the Eastern Border of India and Pakistan, and Its Possible Presence in the Northwestern Part of the Indian Plate Occupied by Kirthar Range in Pakistan
Nusrat Kamal Siddiqui
Exploration, New Horizon Exploration & Production Limited, Karachi, Pakistan
Before break-up of Gondwanaland, around 200 Ma, Indian Plate was juxtaposed with African Plate, whereas its northwestern part was in vicinity of Arabian Plate; hence there was unhindered deposition of sediments across plates.
In Pakistan Precambrian and Paleozoic succession outcrops along foot-hills of Salt & Khisor ranges. Wells drilled in eastern Potwar produce hydrocarbons from Paleozoic. Exploratory wells drilled on Punjab Platform encountered this succession, where Karampur-1 well showed presence of dead oil. Marvi-1 well drilled in Thar Desert encountered about 2 km of Paleozoic succession and also Precambrian. Across border, in India, Baghewala heavy oil discovery is made in Late Neoproterozoic.
Along northwestern margin of Indian Plate, where Kirthar Fold Belt (KFB) is present in Pakistan, large domal structures exist that expose Chiltan limestone of Middle Jurassic age. KFB is, therefore, suitable to confirm presence of Precambrian and Paleozoic, as it can be encountered at drillable depth.
Smewing et al (2002) report that around 9 km of sediments were deposited in KFB region. However, about 4.5 km uplift across post-Miocene Western Boundary Thrust resulted in erosion of around 2-3 km thick Cenozoic and upper Mesozoic rocks that exposed Jurassic rocks in cores. Remaining Mesozoic is estimated to be around 2 km thick in KFB. It is postulated that space is available for accommodating a considerable thickness of sediments which could be of Paleozoic age and older. Gravity-magnetic surveys indicate the basement to be around 8-9 km deep. Peters (1995) has established similarity of oils from Baghewala, Karampur with source rock of Precambrian Huqf Group in Oman. This similarity indicates that Precambrian and Paleozoic succession could have been deposited in KFB while three plates were juxtaposed.