This contribution presents chemical data on clays (SEM-EDS and trace elements) along with bulk organic carbon (delta C-13(org)) isotopes from the Mahadeo-Cherrapunji (MCR) section sediments to evaluate Deccan volcanism-induced paleoenvironmental perturbations across Cretaceous/Paleogene boundary (K/PgB). The assemblages of clay minerals (illite, chlorite, kaolinite, and smectite) in this section under study demonstrated that the climate during the late Maastrichtian-early Danian period was humid to arid/semi-arid. The rare earth element (REE) patterns normalized to chondrite reveal flat, heavy REE (HREE) patterns with negative europium (Eu) anomalies and enriched light REE (LREE) patterns. The MCR section suggests that the basin experienced intermittent oxic to anoxic depositional conditions, as indicated by the low to moderate values of Total Organic Carbon (TOC), V, and U, along with low Ni/Co and U/Th ratio values. The average delta C-13(org) value of MCR section clays is - 24.85 parts per thousand. However, the pre-K/PgB gray calcareous shale layer (MC-12A) in biozone CF1 shows a delta C-13(org) value of - 28.91 parts per thousand, which is significantly (similar to 4 parts per thousand) lower than the immediately lying below and above layers. The meager delta C-13(org) value (similar to 4 parts per thousand) during the K/PgB transition is attributed to the highly anoxic oceanic environment. Elevated levels of CO2 were attained through the release of warm greenhouse gasses resulting from Deccan volcanic activity. The findings of this investigation are supported by the shallow marine Therriaghat (Um-Sohryngkew River) section in Meghalaya, as well as other recognized K/PgB successions worldwide.