Sedimentology And Facies Modeling Of Permian Tobra Formation, Salt Range Pakistan (T-1439) (MFN 6902)

Abstract

The early Permian sedimentary sequence of Salt Range belongs to glacio-fluvial origin of late Paleozoic Ice-age, that marks a complete transition from Ice-age period to greenhouse period. Present research work is aimed to understand the sedimentology and litho-facies of early Permian Tobra Formation from eastern and western Salt Range through a detailed field and laboratory investigations. The field studies comprise of measuring designated litho-sections in Zaluch Section at western Salt Range and Pidh and Tobra Sections in eastern Salt Range where Tobra Formation is exposed, collection of representative samples and recording all sedimentary structures. The present research work determined about 7 litho-facies of Tobra Formation i.e. Matrix-Supported Conglomerate Facies, Clast-Supported Conglomerate Facies, Claystone-Conglomerate Facies, Claystone Facies, Massive Claystone Facies, Massive Sandstone Facies and Pebbly-Sandstone Facies. These Facies expresses glacial influenced debris flow to stream/channel flow deposits. The petrographical studies revealed that the sandstone of Tobra Formation is quartz arenite to lithic arenite and immature to submature. It is interpreted as recycled orogenic tectonic regime during semi humid to humid climate conditions. The formation is comprised of Diamictite conglomerates, mostly having igneous origin clasts. The framework grains observed during petrography, are angular to sub rounded monocrystalline and polycrystalline quartz, Microcline, perthitic feldspar, alkali feldspar, plagioclase, biotite, hematite, chert, muscovite and number of lithic fragments from distinct origins. The geochemical analysis (XRD) finds that quartz, dolomite and albite are the major mineral constituents, palygorskite and dickite are minor constituents. Major element analysis finds out that Tobra Formation sandstone are lithic-arenite and non-marine deposits with increasing maturity; immature to submature, and subalkaline, basic to acidic rocks.