STRUCTURAL AND STARTIGRAPHIC FRAMEWORK OF THE MARWAT-KHISOR RANGES, N.W.F.P. PAKISTAN

IFTAKHAR, ALAM (2008) STRUCTURAL AND STARTIGRAPHIC FRAMEWORK OF THE MARWAT-KHISOR RANGES, N.W.F.P. PAKISTAN. Doctoral thesis, University of Peshawar.

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Abstract

The Marwat-Khisor ranges define an east to northeast-trending fold-thrust belt flanking the mobile perimeter of the Bannu Basin in the south. Detailed mapping in this belt has led to well understanding of its stratigraphy and structural architecture. The stratigraphy of the Khisor Range consists of Paleozoic to Mesozoic platform sedimentary rocks unconformably overlain by Plio-Pleistocene sediments of Siwalik Group rocks whereas the Marwat Range is entirely composed of Siwalik Group rocks of Plio-Pleistocene age. Structures produced by ongoing Himalayan tectonics are well recorded in these ranges and are represented by regional to local scale, parallel to en cehelon folds and thrust faults. Key structural elements of the Khisor Range are the Paniala, Saiyiduwali, Mir AIi, and Khisor anticlines along with a frontal thrust named the Khisor Thrust. The Marwat Anticline constitutes the main structure of the Marwat Range. At the surface, most of these folds have southward-facing asymmetry except the Paniala Anticline, which is north facing. The Khisor Thrust fault is partially exposed along the southern slopes of the Khisor Range where it places Permian strata in its hanging wall over the Siwalik Group rocks in the footwall. Several interpretive structural transects are constructed across the Marwat-Khisor ranges in order to analyze its subsurface style. Projecting surface structures to depth using kink plane bisecting angle techniques, it is found that in Marwat-Khisor ranges basement is not involved in deformation and there is a through-going sole fault at the base of Jhelum Group rocks which separates basement from the overlying sedimentary sequence. Shortening above this basal decollement is the consequence of sequential up-section ramping. The Marwat Anticline is the earliest response to shortening related to a simple structural process-fault bend folding and its evolution is concurrent with the underlying ramp. It was subsequently followed by gradual southward migration of deformation till enough critical taper was achieved to initiate the next frontal ramp from the basal decollement that emerged at surface as Khisor Thrust that accomplish most of the shortening in the frontal boundary of the Khisor Range. Major folds in the Khisor Thrust sheet such as the Paniala, Saiyiduwali, Khisor, and Mir Ali anticlines accommodate bending in the underlying thrust ramp. Orientation of both large and small-scale structures indicate that the Marwat-Khisor structural province is characterized by thin skinned deformed fold-thrust assemblages that define a south-southeast vergent structural system impinging upon the Punjab Foreland. Attitude data on the fold limbs suggest that the prominent fold structures have been evolved as fault-bend folds, being the consequence of contractile deformation related to southward progression of Himalayan deformation. Deformation in the region post-dates the deposition of Plio-Pleistocene Siwaliks indicating that the age of compressional deformation is post Pleistocene. Prerequisites for hydrocarbon generation, accumulation and entrapment such as source, reservoir , seal, and fault related anticlinal culminations are present throughout the study area that proves the hydrocarbon potential of the surrounding region.

Item Type: Thesis (Doctoral)
Uncontrolled Keywords: marwat-khisor ranges, startigraphic framework, stratigraphy, structural architecture, khisor thrust fault, paleozoic rocks, mesozoic rocks
Subjects: Q Science > QE Geology
Depositing User: Muhammad Khan Khan
Date Deposited: 22 Sep 2016 04:58
Last Modified: 22 Sep 2016 04:58
URI: http://eprints.hec.gov.pk/id/eprint/1454

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