Abstract:
The Murree Formation is a part of the Miocene molasses deposits of the
Rawalpindi Group that crops out in Islamabad, Pakistan. The rock sequence of the
formation consists of a series of alternating beds of sandstone, siltstone and shale with
subordinate marls and conglomerates. The sporadic exposures of the formation occur
south of the Main Boundary Thrust (MBT) at Shah Allah Ditta, Barakahu, around Rawal
Dam, G and H Sectors of Islamabad and along the Srinagar Highway. The sandstone of
the Murree Formation is predominantly fine - to medium- grained and moderate to poorly
sorted. The rock contains angular to sub-angular quartz (30-55 vol.%) and feldspar (2-3.5
vol.%) with abundant rock fragments (20-51 vol.%). The cementing material is calcite
which constitutes (14-28 vol.%). The relative abundances of quartz, feldspar and rockfragments suggest the sandstone of the formation as sub-mature whereas the presence of
calcite matrix and angular grains of quartz place it texturally as immature. The observed
accessory minerals include epidote, monazite and tourmaline. The sandstone, on the basis
of quartz, feldspar and rock fragments classify as litharenite and recycled orogenic in the
(Q-F-LF) ternary plots, which might have formed due to rapid deposition in the
tectonically deformed areas. For knowing the potential of the sandstone of the Muree
Formation for utilization as the geotechnical properties obtained include uniaxial
compressive strength (50.9-16.1), uniaxial tensile strength (8.19-2.31), specific gravity
(2.67-2.636) and water absorption (0.59-0.25). Based on the research study, sandstone of
the Murree Formation is considered suitable for dimension stones and construction
material.
