Microfacies Analysis And Interpretation Of Depositional Setting Of Chorgali Formation, Rumli Village, Islamabad

Abstract

This research project deals with the depositional environment and biostratigraphy of the early Eocene Chorgali Formation found in Rumli Village, Islamabad. The Chorgali Formation is well exposed in the study area, having limestone with thin inter-beds of shale. The study involves fieldwork and the laboratory work. Fieldwork involved the collection of fifteen rock samples, followed by petrographic analysis, which led to the recognition of a variety of faunal assemblage, including Nummulites atacicus, Nummulites mamillatus, Nummulites globulas, Assilina spinosa, Assilina granulosa, Assilina laminose, Lockhartia and Milliolide. The study suggests Nummulites and Assilina are index fossils of Chorgali formation. Four microfacies were identified such as Coralline algae mudstone, Peloidal mudstone microfacies, Bioclastic Wackstone microfacies, and Assilina-Nummulites Wackestone microfacies. These microfacies were identified on the basis of faunal content, allochem type and texture. Additionally, petrographic studies were conducted to examine the diagenetic features present within the Chorgali Formation. These studies revealed various diagenetic features that have influenced the formation. The recorded diagenetic features include, recrystallization, fracturing, calcite filled veins and neomorphism. However, these diagenetic features, microfacies and fossil content clearly indicate that Chorgali Formation was deposited in shallow marine environment.