Tracking provenance shift in the Cretaceous-Paleogene sedimentary succession of the Garhwal foreland basin, NW Himalaya using sediment geochemistry and U-Pb detrital zircon geochronology

The present study involving the sediments of Nilkanth and Subathu formations from the Himalayan foreland basin in Garhwal region, NW-Himalaya, Uttarakhand, India focuses on the tectono-sedimentary evolution of the basin in relation to the India-Eurasia collision using sandstone petrography, sediment geochemistry and detrital zircon geochronology. Geochemical proxies including i) higher concentrations of MgO, Ni, Cr, ii) enriched LILE and LREE and iii) flat HREE in Subathu litho-succession as compared to the Nilkanth mixed clastic-carbonate succession, allowed proposing a northern arc-related supply (in addition to cratonic source) for the Subathu Formation as opposed to supply only from the cratonic side in case of Nilkanth Formation. The presence of -90 Ma youngest zircon grain in Subathu sandstone attests to the claim of detrital supply in the Subathu basin from the north. The idea also gets support from the chemical distinction between sandstone samples of the two formations and their tectonic set-ups inferred therefrom. Whereas the upper Cretaceous Nilkanth Formation, deposited in a passive margin set-up at the leading edge of the northward advancing Indian plate, between -125 and 100 Ma and received detritus from the Indian peninsula, collision and forebulge formation resulted in the transgression that triggered Subathu sedimentation with the onset of detritus supply from the tectonically uplifted orogen in the north by Late Paleocene.