Carbon isotope and REE characteristics of the Paleocene–Eocene shallow marine Subathu formation from the NW Himalaya (India) and their paleo-environmental implications

Abstract

Carbon isotope (δ13C) and rare earth element (REE) concentrations in representative samples of the shallow marine Subathu Formation, explored from the Neelkanth and Dogadda sections of Northwestern Himalaya (India) were determined to infer the palaeo-environmental condition during the late Paleocene and middle Eocene. δ13C values show variation of ∼5.0‰ with maximum excursion (−27.34‰) in calcareous sandstone at the basal part and minimum (−22‰) in red shale towards the terminal end. Total REE concentration varies (due to lithology) from 27.23 ppm to 564.35 ppm with an average of 187.60 ppm. The chondrite and PAAS normalized patterns exhibit positive Ce anomaly (0.95–4.45), enriched LREE, and depleted HREE, medium Y/Ho ratio (∼30–45) along with positive correlation between Y/Dy and Y/Ho ratio. In addition, calcite veins present in some shale samples indicate redox sensitive trace elements. The overall REE abundance and distribution suggests highly oxygenated environment under the shallow marine regressive phase of deposition. The depositional setting, biostratigraphical constrained age along with δ13C values and lower TOC suggested an intense warm period, that might be coeval with the Paleocene-Eocene Thermal Maxima event (PETM).