Sedimentology of Lockhart Formation, Ratta Shah Chowk, Taxila, Punjab, Pakistan

Abstract

A portion of the Lockhart Limestone outcrop exposed in the Margalla Hills ranges is investigated for its microfacies analysis and diagenetic fabric. The medium to thick-bedded, nodular, and occasionally brecciated limestone that makes up the majority of the Lockhart Limestone is highly fossiliferous, with thin interbeds of shale and marl. Four microfacies-bioclastic pack-stone, wacke-stone (siliciclastic bioclastic rich sub microfacies), wacke-stone pack-stone and mud-wacke-stone have been found based on thorough petrographic research. The Lockhart Limestone is thought to have been deposited in the fore-shoal mid-ramp, mid-ramp and outer ramp depositional settings based on microfacies research. Lockhart Limestone's Paleocene age has been determined by using age-diagnostic foraminifera, specifically Miscellanea, Lockhartia and Ranikothalia. Numerous diagenetic phenomena, including micritization, neomorphism (aragonite to calcite transformation and production of micro spar), compaction, pressure dissolution (micro stylolites) and cementation (calcite-filled microfractures), define the diagenetic fabric of the Lockhart Limestone. These diagenetic characteristics arise in burying—meteoric and marine diagenetic environments. Based on the outcrop features, microscopic fabric and depositional environment, the Paleocene Lockhart Limestone of Pakistan exhibits traits that are like those of the Paleocene Zongpu Formation (Member-3) of the Gamba-Tingri Basin of southern Tibet.