Microfacies Analysis of Margalla Hill Limestone, Kuzagali, Khyber Pakhtunkhwa, Pakistan

Abstract

This research project deals with biostratigraphy and microfacies analysis of the Eocene Margalla Hill Formation found in Kuza gali, Murree Islamabad. The Margalla Hill Limestone is well exposed in the study area, having limestone with thin interbeds of shale and marl. The study involves fieldwork and laboratory work. Fieldwork involved the collection of twenty rock samples, followed by petrographic analysis, which led to the recognition of a variety of faunal assemblage, including Nummulites atacicus, Nummulites fishtail, Nummulites globules, Assilina, Assilina granulosa, Assilina laminose, Lockhartia, Discocylina, and Alveolina. The study suggests Nummulites are index fossils of Margalla Hill Limestone. Four microfacies were identified such as bioclastic mudstone, Bioclastic wack-packstone microfacies, Bioclastic wackstone microfacies, and Bioclastic mud-wackstone microfacies. These microfacies were identified based on faunal content, allochem type, and texture. Additionally, petrographic studies were conducted to examine the diagenetic features present within the Margalla Hill Limestone. These studies revealed various diagenetic features that have influenced the formation. The recorded diagenetic features include recrystallization, micritization, compaction and neomorphism. However, these diagenetic features, microfacies, and fossil content clearly indicate that the Margalla Hill Limestone was deposited in the shallow marine environment.