Interpretation Of Paleoenvironments Based On Faunal Assembelages & Diagenesis Of Kohat Formation At Sumari Village, Lachi, Kohat Sub Basin, Pakistan

Abstract

The Kohat formation of Eocene age was developed in the Kohat basin of the Himalayan Fold and Thrust Belt in Northern Pakistan. The Kohat Formation shows variable thickness comprising mainly from thin to thick bedded nodular limestone, with intercalations of thinly laminated shales. For micropaleontological examination, the Eocene Kohat formation at outcrop level was measured in the Sumari Village, Lachi, District Kohat, northern Pakistan. Eighteen thin sections were obtained from different samples. Based on primary sedimentary features and lithology, the Kohat formation is subdivided into eight different lithofacies. Thin section studies revealed the depositional environments of formations leading to the identification of three foraminiferal genera as Nummulites, Assilina & Alveolina. Based on petrographic data, six microfacies have been identified, i.e., Nummulitic Pack stone Microfacies. Algal-Miliolid Wackestone-Packstone Microfacies. Bioclastic Pack stone Microfacies. Bioclastic Wacke stone Microfacies. Nummulitic Grain stone Microfacies. Bioclastic Mudstone Microfacies. The characterization of these above facies supports deposition in shallow marine environment. The diagenetic fabric consisting of neomorphism, dissolution, micritization of Kohat formation indicates meteoric-deep burial environment of diagenesis.