Structural Styles, Evolution and Hydrocarbon Prospectivity of the Kirthar Range, Western Pakistan: Deformation and Hydrocarbon Accumulation Along a Transpressional Plate Margin and Fold-Thrust Belt

Daniel Schelling¹, Amir Ayub², Shahid Zahidi³, Ahmed Naveed⁴, John Hurst⁵, Phil Maclaurin⁶, and Patrick Bird^3
1 Structural Geology International, Salt Lake City, UT
² Moh Geological Consultants, Calgary, AB
³ Premier-Kufpec Pakistan, Islamabad, Pakistan
⁴ Premier Oil, London, United Kingdom
⁵ Novus West Asia, Dubai, United Arab Emirates
⁶ Premier Oil, Singapore, Singapore, Singapore

Located along the presently active, western plate margin to the Indian subcontinent, the north-south trending Kirthar Range of western Pakistan includes a complex set of structural systems that have developed as a result of transpressional deformation since the initial collision of the Indian subcontinent with Eurasia and the Afghan microcontinent. Within the southern Kirthar Range, structural systems have developed primarily as a result of thin-skinned detachment tectonics, with fault-propagation, hanging wall anticlines defining the primary hydrocarbon targets (eg. the Zirkani gas discovery). Further north, however, within the central and northern Kirthar Ranges, compressional tectonics has resulted in significant uplift, on the scale of 5 to 10 km, along deep-seated fault systems that originate below the massive, Jurassic Chiltan Limestone. Broad structural uplifts, bounded by medium to high-angle fault systems, define the primary hydrocarbon targets of the central Kirthar Range, which include the Bhit and Bhadra gas discoveries. Along the Quetta syntaxis, where the north-south trending Kirthar Range merges with east-west trending structures of the southern Sulaiman Range, complex structural interference patterns have resulted in the formation of the Zarghun structure, along which gas was discovered in 1997. Additional structural complexities have been identified along the western edge of the Kirthar uplift, where structural overprinting has resulted in the deformation of previously developed compressional systems by late-stage strike slip systems. The interaction of compressional, transpressional, and strike-slip structural systems of the Kirthar Range has therefore resulted in complex structural styles that must be understood for successful hydrocarbon exploration.

AAPG Search and Discovery Article #90039©2005 AAPG Calgary, Alberta, June 16-19, 2005