Late Mesozoic Sedimentary Megacycle in the Rifted Haro Trough, Hazara, Pakistan and its Hydrocarbon Implications in the Northern Rim of the North West Himalayan Basin
Late Jurassic to Late Cretaceous Haro megacycle (Chichali, Lumshiwal, and Kawagarh formations) is geographically situated between Nathiagali, Murree, and Jhelum faults. This megacycle is unconformably contained between the Middle Jurassic Samana Suk platform carbonates and the Early Tertiary carbonates. The megacycle consists of two unconformity bounded sequences: (1) above the top-Bathonian unconformity with Late Oxfordian basal belemnite bed, two coarsening up cycles, and a pelecypod coquina cycle bounded by Late-Albian unconformity; (2) middle/Late Turonian to Campanian planktonic foram wackestone-packstone, a carbonate slope breccia,and a localized Campanian/Maestrichtian low stand Jamhiri Sandstone bounded by the Basal Tertiary unconformity. The Sequence 1 clastic cycles were supplied from the east and prograded westward axially in the basin. At least two major marine transgressions are recorded in the Haro megacycle. The Cretaceous tectonics, the sedimentary facies and their relations to the bounding faults, suggest the Haro Trough was an extensional rift basin. The original basin bounding and internal normal faults have later been inverted as thrusts. Regional time shifts at the base of the Late Mesozoic megacycle and the collapse of underlying carbonate platform, suggest the rifting started in the north and gradually migrated southward in Pakistan.
The horsts bounding the Cretaceous grabens are attractive for hydrocarbon exploration. The deformed sedimentary basins in northern Pakistan should be reevaluated for identification of horsts to better target hydrocarbons exploration in the early Tertiary and the older rocks.