Abstract:
The geological structures and seismology of Northern Pakistan are affected by
salt tectonics. These salts or evaporates are the major contributor, which are balancing
northward thrusting and south verging uplifts in this part of Sub Himalaya i.e., in back
bulge. Also, the role of basements related normal faults is important, which are forming
ramp-flat geometries where these incompetent strata (evaporites) are assembled and
give rise to popup structures like Balkassar, Joya Mir, Chak Nourang and diaprism like
Salt Range Thrust (SRT) in the southern part. The Study is lies in the back bulge of the
Sub Himalaya or in the southern part of Potwar platform sequence. Balkassar and Salt
Range structures are evaluated to know the behavior of the salt in Structure
development where popups and diaprism is prominent. Basement faults under these
structures are almost running in EW direction and assembling the maximum thickness
of salts even it exceeds from its actual thickness (800-1000 m). This study is an attempt
to investigate the role of salt in the geological deformation of the Salt Range-Potwar
Plateau using well log interpretation, Burial history of wells and seismic
interpretations, seismic data facilitate to construct the sub-surface models of the study
area i.e., Kalar Kahar and Balkassar area. The structural restoration practice was done
alone seismic lines (KK-13 and PBJ-1) to calculate difference appeared due to the
shortening. Areal distance of the two seismic lines (tied with jump tie method & well
log) is 43 km but when it is restored in a form of platform sequence the distance is 78
km. Therefore, difference or shortening of about 35 km. Burial history shows composite
unconformity from the top of Cambrian to Lower Permian and again remained exposed
from middle Permian to Middle Paleocene age. Temperature data shows increasing
temperature and pressures with respect to depth i.e., 2 degrees per 100 m. Sonic/density
log also gives compaction trend with respect to the depth but it falls dramatically in the
evaporites due to the very low competency i.e., from maximum 2.9 g/cm3 of dolomite
to salt about 1.1 g/cm3. While talking about the reservoirs and hydrocarbon
prospectively, Khewra Sandstone has very good results. But not producing in the whole
basin because of the presence of sealing strike slip fault in Balkassar structure.
