PETROGRAPHIC CONTROL ON GEOMECHANICAL CHARACTERISTICS OF NAMMAL FORMATION, SALT RANGE, PAKISTAN

Abstract

The Nammal Formation of Eocene age along the Salt Range Thrust (SRT) is present in all the three sections of Salt Range. The main concern of this research is to investigate the petrographic control on geomechanical characteristics of Nammal Formation. The limestone of the Nammal Formation has been detailed studied under the microscope. Strength and the mechanical tests are also applied. According to Dunham’s scheme of classification, the petrographic study has suggested that the limestone of Nammal Formation of Western Salt Range is bioclastic mudstone. At the Sethi section of Central Salt Range, the limestone has been named as Bioclastic wackestone. The limestone of the Nammal Formation of Eastern Salt Range is named as the Bioclastic wacke-packestone. The observed diagenetic features include such as neomorphism, dissolution and three types of carbonate cement. The geomechanical results in which the strength tests (UCS, Brazilian and Schmidt Hammer test) and aggregate tests (Loss Angeles abrasion, Water absorption, specific gravity and sulfate soundness test) are indicating that this limestone can be considered for engineering and construction. Micrite and sparry calcite cement helps in increasing strength values while the presence of calcite veins, bioclasts and planktons may reduce the strength values. The presence of marl portion in Nammal Formation is poor for the engineering and construction.