Geometry and Evolution of the Sulaiman Fold Belt and Hydrocarbon Prospects

Jadoon, Ishtiaq A.¹
(1)Department of Environmental Sciences, COMSATS Institute of Information Technology, Abbottabad, Pakistan.

The lobate, Sulaiman fold belt covering about 200,000 square kilometer along the western terminus of the Indian subcontinent is considered to be the most prolific hydrocarbon province of Pakistan. Integrated surface geology and subsurface seismic data has allowed recognizing the geometry and evolution of the Sulaiman fold belt as a passive-roof duplex, with the absence of a thrust fault at the mountain front and presence of surface monoclines with exposure of progressively older strata towards the internal parts of the system. A key balanced cross-section across the Sulaiman fold belt exhibits fold-and-thrust structures in the form of two detachment folds (Sui and Loti gas fields) with about 10 km depth of the detachment in the Triassic or older strata at the mountain front. They are transformed into a passive-roof duplex geometry further north. The duplex structures are characterized by the fault-bend folds and anticlinal stacks, as prospects, with an overlap of a considerably long roof sequence. The roof-sequence is devoid of any thrust far about 60 Km north of the tip of the first duplex. It is, however, breached by the foreland and hinterland verging reverse faults, bounding tight anticlines of Cretaceous and younger strata, in the central Sulaiman fold belt. These reverse faults of limited lateral extent and displacement are recognized not to qualify the definition of a nappe structure. They are interpreted to be related to the active evolution of a passive-roof duplex, with abundance of seismic activity in the central Sulaiman fold belt. Some of these faults are observed to show a dominant component of dextral strike-slip displacement, suggesting imprints of transpression and rotation along the western edge of the Indian plate.

AAPG Search and Discovery Article #90135©2011 AAPG International Conference and Exhibition, Milan, Italy, 23-26 October 2011.