Microfacies Analysis and Source Rock Potential of Nammal Formation, Western Salt Range, Pakistan

Abstract

The present study investigates the microfacies and source rock potential of the Eocene Nammal Formation in the Nammal Gorge Section, western Salt Range, Pakistan. The Nammal Formation consists of light grey to creamy color limestones, olive green to grey shales and light grey marls. Twelve rock samples of limestone were collected for microfacies analysis and nine samples of limestone and shale were analyzed for determination of Total Organic Carbon (TOC) content and source rock potential of the Nammal Formation. Thin section studies of rock samples revealed four microfacies, i.e., mudstones, wackestones, wackestones to packstones and packstones. Microfacies analysis showed that intraclast, planktons and some small benthic foraminifera, pelecypods and opperculina are present in the Nammal Formation. The type of microfacies and abundance of planktons suggest deposition on a carbonate ramp platform within outer neritic to distal shelf environment in the study area. The Nammal Formation presents a coarsening upwards trend and rise in sea level during its deposition. The average TOC value of nine samples of shale is 0.0812 which shows very little organic matter and poor source rock potential of the Nammal Formation.