Reconnaissance Microfacies Studies of Margala Hill Limestone, Jabri Area, Southern Hazara, Pakistan Filed under Vol-05

Abstract

  The Margala Hill Umestone of Early Eocene age from Jabrl Area, Southem Hazara has been studied in detail for internal units, microfacies and diagenetic fabrics. A total of ten microfacies and five internal facies units have been defined. The ten microfacies from bottom to top are mudstone (fossiliferous micrite), wacke- to packstone (biomicrite), grainstone (biosparite), wackestone (biomicrite), packstone (biomicrite), packstone (sparbiomicrite), packstone (biomicrite), mud to wackestone (biomicrite), mudstone (fossiliferous micrite) and packstone (biomicrite). The five intemal facies units from bottom upwards are biomicrite, biosparite, biomicrite, sparbiomicrite and biomicrite. These units correspond to fluctuations in sea level. The study of texture, structure and faunal assemblages shows that the Margala Hill Umestone was deposited under open shelf marine environments. The blomicrltes were deposited In low energy environment I.e. below the wave base while biosparite was deposited In high energy environment and at relatively shallower depths. The sparbiomlcrlte has a complex history. Deposition commenced in low energy environment. But due to change In sea level the still porous biomicrite was transferred to higher energy environments where spar cement was Introduced. This paper also deals with diagenetic fabrics and their origin.