Provenance and palaeo-weathering pattern of the Carboniferous Fenestella Shale Formation, north-west Tethys Himalaya, India

Using the integrated approach of sedimentology, petrography and geochemistry, we tried to understand the provenance, palaeo-weathering and depositional pattern of Carboniferous Fenestella Shale Formation (consisting of shales and sandstones) exposed in the Kashmir Valley, north-west Tethys Himalaya. Five lithofacies are identified from base to top of the studied succession, viz., quartz-arenite facies, pebbly sandstone facies, sandstone-siltstone facies, silty-shale facies and shale facies collectively suggest a shallow and deep-water depositional environment. The dominance of small-scale bi-directional cross-stratification relative to large-scale planar cross-bedding in the quartz-arenite facies intercalated with shale facies reflects deposition in a shelf to shore setting during regressive to transgressive phases. The discrimination diagrams also suggest the passive margin depositional setting of these rocks. The chemical index of alteration (ranging from 53 to 77) and weathering index of Parker (ranging from 37 to 57) reflect that the source rocks underwent a low-to-moderate degree of chemical weathering. The presence of plutonic (granitic) rock fragments and dominance of heavy mineral grains, e.g., zircon, rutile and tourmaline in the Fenestella sandstones suggest plutonic rocks as pristine source rocks. Based on coupled sedimentological and geochemical characteristics and available geochronological data sets, it is suggested that the Neoproterozoic Pan-African granites situated south of the Tethys Himalaya could be the possible source rocks for Fenestella Shale Formation.