Integrated microfacies analysis of lower Paleogene carbonate rocks of Kasanwala area, Western Salt Range, North Western Himalayas, Pakistan

Abstract

The main purpose of this study is to analyze the microfacies and biostratigraphy of lower Paleogene carbonate rocks (Lockhart Limestone, Nammal Formation and Sakesar Limestone) from the Kasanwala section in Western Salt Range. Several samples were collected during field work to prepare the thin sections for rock identification and to identify the microfacies of above mentioned formations. The results depicts that Lockhart Limestone is composed of nodular limestone with intercalated shale and is dominated by larger benthonic foraminifera. The measured thickness of Lockhart Limestone in study area was 37m. Four microfacies of Lockhart Limestone have been observed after thin section analysis namely; Bioclastic Mudstone, Lockhartia Wackestone, Miscellanea Packstone and Lockhartia Packstone microfacies. The Nammal Formation consists of alternating beds of medium to dark grey limestone with some clay and shale and is highly fossiliferous in some parts. In this section, Nammal Formation was 56m thick. Five microfacies of Nammal Formation have been identified, namely ; Bioclastic Mudstone, Nummulitic Wackestone, Bioclastic Wackestone, Peloidal Wackestone and Nummulitic Packstone microfacies. The Sakesar Limestone is composed of cream to light grey nodular massive limestone with chert nodules in upper part. The observed thickness was 36m. Three microfacies of Sakesar Limestone have been proposed after comprehensive microscopic analysis namely; Algal Mudstone, Bioclastic Mudstone and Assilina Wackestone microfacies. On the basis of observed fauna, its bathymetry and the microfacies framework, it can safely be concluded that these lower Paleogene rocks were deposited in shallow marine, open shelf environment with free circulation of water.