Towards a Better Understanding of the Structural Style and Hydrocarbon Potential of the Southern Kirthar Fold Belt (Pakistan): New Insights from Field Observation and Remote Sensing
Ahmad, Sajjad¹; Qayyum, Abdul²; Khan, Mohammad I.²; Rehman, Gohar¹
¹Department of Geology, University of Peshawar, Peshawar, Pakistan.
²Exploration, MOL Pakistan, Islamabad, Pakistan.
The Kirthar fold belt (KFB) of south Pakistan is the southernmost part of a regional fold-thrust belt which skirts the outer border of Himalayan continental collision zone. The structural style and evolution of the Kirthar fold belt is mainly affected by the tectonics of the Chaman and Ornach-Nal transform zone located in the west and a better understanding of its structural fabric is crucial to elucidate the impact of Chaman transform zone on its structural style and ultimately hydrocarbon potential. The external foothills of the southern KFB have yielded significant commercial discoveries of hydrocarbons till now while the main KFB is still a challenge and less explored province. The current observations in southern KFB reveal that the main KFB is separated from its eastern foothills by a north south to north northwest trending, steeply east-dipping back thrust namely Kirthar Fault detached within Ghazij Shale. The structural style of eastern foothills and the main KFB is comprised of a series of northwest trending en echelon fold-thrust assemblages detached within Eocene and Jurassic to Cretaceous rocks respectively. The folds orientation in the main KFB and its eastern foothills are oblique to the Kirthar Fault and is consistent with that of a right lateral wrench zone structural pattern. The structural analysis in the southern KFB suggests that the initial fold belt was shaped as a result of the eastward emplacement of the Bela Ophiolite onto Indo-Pakistani Plate during Late Paleocene. The right lateral wrench-related structural pattern is believed to be the latest activity attributed to left lateral strike slip adjustments of the Afghan and Indo-Pakistani Plate along the Chaman and Ornach-Nal transform zone. The Eocene-cored fold strand which immediately lies west of the Kirthar Fault is in good position to receive the hydrocarbons from the generation and expulsion front in the east. This idea is well supported by the westward asymmetry caused by the west-verging Kirthar Fault.
AAPG Search and Discovery Article #90155©2012 AAPG International Conference & Exhibition, Singapore, 16-19 September 2012