Microfacies Analysis and its Implications for Depositional Environment of Margala Hill Limestone from Khaira Gali Road Section, North Eastern Hazara, Pakistan

Stratigraphic section of Margala Hill Limestone exposed in the Khaira Gali road section of the Hazara Basin, northwestern Himalayas has been measured, logged and sampled. The 96m thick section of Margala Hill limestone mainly consists of medium to thick bedded nodular limestone with intercalations of shale. This high resolution petrographic study of the formation has been done with an integrated approach of sedimentology, paleoecology and biostratigraphy and it mainly shows wackstone to packstone carbonate texture with different assemblages of Larger Benthonic Foraminifera e.g. (Assilina spinosa, Nummulites globulus, Ranikothalia sindensis, Nummulites mamillatus, Assilina subspinosa, Nummulites atacicus, Assilina granulosa, Operculina patalensis, Assilina laminosa, Ranikothalia nuttalli, Lockhartia conditi, Ranikothalia sahni, Lockhartia tipperi, Discocyclina dispansa, Discocyclina ranikotensis and Quinqueloculina), Bivalves and green algae. Five types of microfacies have been interpreted on the basis of carbonate texture and skeletal grains observed in thin sections. These microfacies include Rotaliids-milliolids mud-wackstone, Algal- bioclastic packstosne, Nummulitic wack-packstone, Assilinids wack-packstone and Discocyclina- Ranikothalia wack-packstone microfacies. The presence of these assemblages draws the conclusion that the deposition was occurred in closing Neo-Tethys on an inner to middle shelf environment at the northern extremity of the Indian Plate. Based on age diagnostic Foraminiferal assemblages, Ypresian, Early Eocene age has been designated to the Margala Hill Limestone.