Sedimentary Facies and depositional environment of the Lower Eocene shallow shelf carbonate deposit, the Sakesar Limestone, Salt Range, Pakistan

DOI: 10.5176/2251-3353_GEOS14.22

Authors: Shahid Ghazi, Pervaiz Khalid, Aftab Ahmad Butt, Sadaf Sharif and Tanzila Hanif

Abstract: The Lower Eocene (Ypresian) Sakesar Limestone is well exposed in the Salt Range, Pakistan. It comprises 30-35 m thick succession of interbedded nodular limestone, marl and shale. The present study is focussed on detailed sedimentological and biostratigraphical analysis of the Sakesar Limestone based on the data of five stratigraphically important sections (Khajula, Tatral, Badshah Pur, Sardhai and Nilawahan) from the Salt Range. Nine diagnostic microfacies are recorded including; Bioclastic wackestone, Assilina-Nummulitic packstone, Nummulitic wackestone, Nummulitic-Assilina packstone, Bioclastic mudstone, Nummulitic-Alveolina wackestone to packstone, Rotaliine wackestone to packstone, Bioclastic mudstone and Nummulitic-Alveolina packstone. Several species of larger foraminifera have been recorded which include Nummulites mamillatus (Fichtel and Moll), Nummulites atacicus Leymerie, Assilina spinosa Davies and Pinfold, Assilina subspinosa Davies and Pinfold, Assilina laminosa Gill, Assilina granulosa (d’Archiac), Lockhartia tipperi (Davies), Lockhartia conditi (Nuttall), Discocyclina dispansa (Sowerby) and Alveolina globula Hottinger. During the Lower Eocene time shallow marine sedimentation rich in larger foraminifera took place in the carbonate ramp platform environment in the Salt Range region. The assemblage of larger benthic foraminiferal and detailed microfacies analysis reveals the inner neritic depositional environment of the Sakesar Limestone. Isotopic records of stable carbon and oxygen also indicate marine depositional environment for the Sakesar Limestone.

Keywords: Lower Eocene, Sakesar Limestone, Larger benthic foraminifera, Inner neritic, Salt Range