Tertiary Geology of Part of South Makran, Baluchistan, West Pakistan

Abstract

The South Makran basin in the southern part of the Baluchistan basin was the site of considerable clastic sedimentation from the Oligocene onward. The sediments formed a wedge thickening seaward from the present Gokh Prush Band at a rate of 160 m/km to a total thickness of at least 10,000 m along the coast of the Arabian Sea. The sequence comprises the Panjgur Formation of Oligocene to early Miocene age and the Miocene to Pliocene Makran Group. The rock types are shale, mudstone, conglomerate, and minor coquina and limestone. The predominance of argillaceous and sandy detritus indicates marked subaerial erosion of uplifts on the north. The dominant structural trend is east-west. The structure on the north is complex, with tightly folded asymmetric anticlines and synclines, many overturned, associated with transverse faults and high-angle thrust faults. There are indications that salt intrusions were important in producing local structure along the coast and offshore. The folds are believed to be disharmonic, having been produced by southward gliding over plastic argillaceous sediments above the Eocene to Cretaceous carbonates that formed the rigid floor of the post-Eocene basin. Only four wells have been drilled for oil in the study area, and they tested only three structures. Many untested possibilities are believed to remain. Water resources can be augmented by construction of a series of dams to trap the seasonal rainfall in the intermittent stream courses.