Acta Musei Moraviae

Petrographic investigations of the sandstone of the Dhok Pathan Formation, South Eastern Hazara, North Pakistan, Implications for the Provenance

In this study, the sandstone of the middle part of the Dhok Pathan Formation was studied in detail for the petrographic-based provenance at the South Eastern Hazara. The outcropping clastic sequence of the area reveals complex braided fluvial depositional conditions dominated during Pliocene period. The interbedded channel facies (sandstones) and floodplain facies (shales and some specific sandstone units), in varying proportions, differentiate individual formation in the Siwalik Group. The watercourse sediments are the product of aggrading fluvial sedimentation and are distinguished by a succession of upward-fining sandstones overlain by mudstones. Most of the sandstone units in the study area have been observed as multistoried and comprised of composite sand bodies reflecting a mixed fluvial depositional mechanism. The petrographic analyses of different samples collected from the study area of the middle sandstone horizon of the Dhok Pathan Formation reveals abundant quartz, feldspar, rock fragments along with variable amounts of several accessory minerals such as epidote, garnet, jarosite and clay minerals. The feldspar grains show alteration to chlorite, kaolinite and other secondary minerals. Calcite, clay minerals, silicious and iron oxide are present as cementing material and their grains show poor to moderate sorting. Rock designated on the basis is lithic arkose to Feldspathic litharenite considering the Folk’s classification of sandstone. Rock fragments observed in the petrographic analysis provide indications about provenance. These assemblages of rock fragments also suggest that the source rocks were rich in igneous to metamorphic ensemble in addition to sedimentary assimilation. By plotting the provenance diagram of Dickenson, showing that the source rocks fit in the zone of recycled orogen.