Surface and subsurface data from the Sulaiman thrust belt show that nearly all
the 10 km thick sequence of dominantly platform (>7 km) and molasse strata is detached
at the deformation front. These strata thicken tectonically to a minimum of 20 km in the
hinterland of the Sulaiman fold belt without significant thrust faults at the surface. The
balanced structural cross-:section suggests that the tectonic uplift in the Sulaiman fold belt
is a result of thin-skinned, passive-roof duplex style of deformation. The duplex
sequence of Jurassic and older rocks is separated from the roof sequence by a passive-back
thrust in thick Cretaceous shales. The passive-roof sequence remains intact for
about 150 km and becomes emergent along a passive-back thrust in the hinterland. The
structures are expressed at the surface by fault-related folds in the foreland and out-of-sequence
structures (secondary faults and related pop-ups) in the interior. The duplex
structure varies from fault-bend folds to anticlinal stacks, and hinterland dipping
duplexes. Progressive deformation reveals a series of structural and geometrical features
including: (1) broad concentric folding at the fault tip; (2) development of a passive-roof
and duplex sequence; (2) forward propagation of the duplex as critical taper is achieved;
(4) tear faults and extensional normal faults within the overthrust wedge; and (5) out of
sequence (secondary) thrusting. The 349 km long balanced cross-section from the
Sulaiman fold belt restores to an original length of 727 km that provides 378 km of
shortening in the cover strata of the Indian subcontinent. Minimum estimate of
shortening is 328 km. Modelling of the Bouguer gravity profile from the Sulaiman
foredeep across the Indian/ Afghan collision zone suggests the depth to the Moho at the
Sulaiman deformation front is about 36 km. Depth to Moho increases northward with a
gentle gradient of 1.1° (20 m/km) for 280 km to the hinterland where the depth to the
Moho is about 42 km. About 150 km north across the Khojak flysch the Moho gradient
steepens abruptly to about 7.8° (136 m/km) to attain an average depth of about 57 km in
eastern Afghanistan. This suggests that the Sulaiman fold belt is underlain by transitional
crust associated with the western passive margin of the Indian subcontinent. / Graduation date: 1992
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/36541 |
| Date | 20 May 1991 |
| Creators | Jadoon, Ishtiaq Ahmad Khan |
| Contributors | Lawrence, Robert D. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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