Abstract:
This research work is based on the structural evaluation and problems
associated with the geological mapping of the Margalla Hills. Area in the north of
Islamabad is selected for this research. In this area repetition and miss matches of the
stratigraphic formations indicate the presence of folds and faults at a map able scale.
Main boundary thrust, Talhaar thrust, Talhaar syncline, Pir Sohawa anticline and
Sanghara anticline are the major structures present in this area. MBT is frontal thrust
marked in the field by faulted contact of Jurassic Samanasuk Formation and Murree
Formation. Outcrop folds are observed in the field involving shale of lower member
of Margalla and Patala Formation. These outcrop scale folds are formed as secondary
folds in major folded structures due to competency contrast and strain
accommodation. The chemical weathering of limestone has obscured the primary
bedding foliation so structural mapping in this area through satellite imagery could
yield wrong orientation research. The fractures are very well developed which often
reveals to be the bedding. So, proper care must be taken for advanced geological
mapping in this area. Two thrust sheets, Talhaar thrust sheet and Margalla thrust sheet
are present in the study area. Theses thrust sheets are bounded by Talhaar thrust and
Main boundary thrust respectively. The synclines and anticlines are formed within
thrust sheets to accommodate the strain resulted by southward progression of
Himalayan induced deformation. The mollasse sediments are restricted to the south of
MBT and no evidence of these depositions is recorded in north of it, which suggests
that area didn’t act as depocentre for the accumulation of mollasse in Miocene and
younger time.
