Abstract:
This research is unified sedimentological approach to analyze microfacies, diagenetic characteristics and evaluate the biostratigraphy of Lockhart Limestone of Nammal Gorge area, Western Salt Range, Pakistan. The Paleocene rocks of Nammal Gorge form one of the important stratigraphic sections in Pakistan. This study investigated 4 main microfacies and 13 sub-microfacies of Lockhart Limestone by comparing each microfacies with Dunham Classification Scheme (1962) and points counting method. The grainstone, packstone and boundstone microfacies and their sub-types dominate the observed thin sections, whereas the wackestone microfacies are less common in the study area. There are six sub-microfacies of grainstone and three sub-microfacies of packstone and boundstone respectively, strongly suggests that the Lockhart Limestone was deposited in moderate to high energy environment. The presence of Foraminifera; like Lockhartia sp, Miscellanea sp, Assilina sp, Operculina sp, Ranikothalia sp, Millliods, Textularia sp, and Globogerina linaperta etc has helped to determine the environment of deposition was shallow marine. Lockhartia sp, was dominantly found in the studied thin sections, that is index fossil of these Paleocene rocks. Moreover the diagenetic alterations like aragonite to calcite conversion, diagenetic alterations like physical compaction, chemical compaction, stylolamination, suture seams, brecciated stylolitic fabric, stylolitization, Nodular stylolitic fabric, aragonite to calcite conversion etc, was observed in the study. Nodular stylolitic fabric along with aragonite to calcite conversion is believed to be occurred in Inner Ramp facies. The establishment of micorfacies, biostratigraphy and diagenetic alterations patterns of Lockhart Limestone suggest that these rocks were deposited in Inner Ramp Lagoonal environment. .
