Physico-mechanical and petrographic analysis of the Margalla Hill Limestone, Islamabad, Lesser Himalaya, Pakistan

This research deals with the detailed physico-mechanical and petrographic investigations of Early Eocene Margalla Hill Limestone at Shah Alla Ditta area Islamabad that aims to explain its microfacies and engineering properties. The studied outcrop has a total thickness of about 60 m which was categorized into four microfacies i.e., bioclastic mudstone, bioclastic mud-wackestone, bioclastic wackestone and bioclastic wacke-packstone. Based on the faunal assemblage, allochemical and orthochemical constituents, the identified microfacies are interpreted to be deposited on the inner ramp lagoon to middle ramp environments. Physical and mechanical properties such as water absorption, specific gravity, bulk density and unconfined compressive strength (UCS) were investigated and correlated with micrite, bioclasts and porosity. Statistical relationship of UCS with micrite, bioclasts and porosity are established through linear regression analysis, which showed that micrite has a positive relation with higher regression coefficient values ( R 2 = 0.98) while bioclasts ( R 2 = 0.96) have a negative trend with UCS. The physical properties reveal that an increase in micrite content resulted in an increase in specific gravity and bulk density but consequently a decrease in water absorption and porosity. On the other hand, bioclasts content shows a negative relation with the specific gravity and bulk density but a positive relation with water absorption and porosity.