Sedimentology and Palaeoenvironmental Reconstruction of the Early Cambrian Kussak Formation, Salt Range, Pakistan

Comprehensive sedimentological and sequence stratigraphic analyses of the Kussak Formation were carried out at the Nilawahan Gorge, the Karuli Section and the Khewra Gorge, Pakistan. The studied Kussak Formation has been grouped into: (1) bioturbated mudstone, (2) interbedded sandstone/shale, (3) sandy dolomite, (4) glauconitic sandstone and (5) laminated sandstone and siltstone. Hard to friable sandstone is present with condensed neobolus beds in the mud at the top. Bioturbation and glauconite are in middle parts, while a few beds of sandy dolomite are also present in the upper and middle parts of the Kussak Formation. These five depositional sequences had developed during the phase of transgression. Mineralogically, the average modal composition classifies it as quartz arenite. Rock fragments belong to the igneous origin, and feldspar grains most likely indicate an igneous and metamorphic source. The field and petrographic study indicate that the source area belongs to arid and semi-arid environments. Presence of wavy and flaser bedding indicates tidal flat deposition. Burrows, mud cracks, and synaeresis cracks indicate supra-tidal environment. Subsurface data show the finning upward sequence that confirms the deposition during transgression. In summary, the environment of deposition is subtidal, intertidal to supra-tidal environment. Palaeogeographic setting shows that the Kussak Formation source belongs to Aravalli and Malani ranges.