MICROFACIES AND DEPOSITIONAL SETTING OF THE EARLY EOCENE CHOR GALI FORMATION, CENTRAL SALT RANGE, PAKISTAN

Abstract

The Early Eocene succession is well exposed in the Central Salt Range; Pakistan
consisted of the Nammal Formation, the Sakesar Limestone and the Chor Gali Formation. The present
work is focused on detailed microfacies and depositional setting of the Chor Gali Formation in the Salt
Range. Four stratigraphically important sections Khajula, Tatral, Badshah-Pur and Karuli were
measured. Twenty five samples were collected and analyzed from these sections to illustrate the
temporal as well as spatial variations in facies. The thickness of the formation varied from 20 to 30
meters. Formation has predominantly composed of thin to well bedded limestone, shale and marl. The
limestone units are argillaceous, marly and rich in larger foraminifers while the shale was highly
fossiliferous and variegated in colour. Six dominant litho-units have been established based on the
field observations. The microfacies analysis allowed identifying and describing diagnostic microfacies
including bioclastic mudstone, bioclastic wackestone, bioclastic packstone and bioclastic grainstone.
The study of benthic larger foraminifera revealed ten age diagnostic species; Nummulites mamillatus
(Fichtel and Moll), N. atacicus Leymerie, Assilina spinosa Davies and Pinfold, A. subspinosa Davies
and Pinfold, A. laminosa Gill, A. granulosa (d’Archiac), A. placentula (Deshayes), Lockhartia tipperi
(Davies) and L. conditi (Nuttall). Field observations and microfacies analysis suggested that the
deposition of formation took place in inner shelf conditions. Presence of shallow water benthic larger
foraminifera also support inner shelf environment for the Early Eocene Chor Gali Formation.