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Abstract: Tectonic Style of the Sulaiman Range (Pakistan), A View from Analog Modeling

Nadine Ellouz, Francine Benard, Jean Letouzey, Carla Muller, Francois Roure, Azam Malik, Tariq Jaswal, Tahir Maqsood

Located 500 km south of the Main Boundary Thrust, the Sulaiman range results from two synchronous tectonic movements: a Tertiary collision related to frontal or oblique subduction of the Indian Plate underneath Eurasia, and, westward, a large left- lateral movement along the Chaman Fault accommodating the northward motion of India.

The inner units of the foldbelt consist of folded and thrust Paleozoic to Eocene formations. Eroded material was deposited in the foredeep basins as Miocene and younger sediments (Siwaliks).

Inherited from extensive tectonic episodes during the Mesozoic, the basement registered N-S and NW-SE trending faults, defining an irregular shape of the margin. Some paleohighs were individualized and, locally, compressionaly reactivated.

The tectonic features of the folded units and underthrust autochthon have been characterized along balanced cross-sections. The restoration of these sections has allowed an estimation of the shortening rates, the timing and the 2D geometry of the deformation.

To estimate the 3D geometries, sand-box model analysed with X-ray tomography have been used. We tested several boundary conditions simulating the:

- heterogeneities of the substratum due to pre-Tertiary tectonic events;

- distribution of detachment levels: pre-Middle Jurassic, Lower Cretaceous; and Lower Eocene shales;

- two episodes of deformation separated by an erosion phase.

The sand-box modeling demonstrated the importance of the pre-orogenic basement's shape, illustrated by the development of en echelon folds. Together with the structural restorations, the 3D modeling was helpful for understanding the deep architecture of the Sulaiman range and the chronology of deformation.

AAPG Search and Discovery Article #90956©1995 AAPG International Convention and Exposition Meeting, Nice, France