Outcrop geology, microfacies analysis and depositional environments of Chorgali Formation from Bhattian and Gharaga, Southern Hazara basin Pakistan

Abstract

In Hazara Basin, Early Eocene is represented by carbonate succession of Chorgali Formation which is mainly composed of limestone with marls and calcareous shale. Limestone is predominantly marly and argillaceous in nature. Two Stratigraphic sections of Chorgali Formation exposed at Gharaga and Bhattian villages have been completely examined and sampled for outcrop characteristics, petrography, microfacies and depositional settings. These sections have both well preserved lower and upper contacts with Early Eocene Margalla Hill limestone and Middle Eocene Kuldana Formation, respectively. The petrographic analyses reveal that Chorgali Formation exposed at Gharaga and Bhattian sections yields abundant Eocene foraminifers along with other fauna and their broken shells. On basis of outcrop data and detailed petrographic analyses, five microfacies are recognized including Nummulites-Lockhartia wackestone to packstone (MF-1), Nummulites- Assilina wackestone to packstone (MF-2), Ostracods-Miliolids packstone (MF-3), Marls Microfacies (MF-4) and Calcareous shale Microfacies (MF-5). Comprehensive microfacies, palaeoecological and outcrop data reveal that deposition of Chorgali Formation was occurred on mid ramp settings with some deposition in attached to partially restricted lagoonal area of inner ramp and proximal part of outer ramp.