Abstract: The Permo-Carboniferous depositional sequence of Lower Gondwana in Sikkim Lesser Himalaya wasinvestigated through an integrated approach of lithological, petrological, and geochemical studies. Lithologically,it is characterized by glacial diamictite at the base and shale-sandstone facies at the top of a sequence which isinterpreted as a glaciomarine deposit. Coarser sandstone and massive diamictite composed of quartz, feldspar,muscovite, zircon, and other lithic fragments are observed in thin section. Geochemistry of all studied samples fromthe Rangit Pebble Slate Formation shows the dominance of silicon dioxide compared to other elemental oxides.The tectonic discrimination diagram positively infers passive margin sedimentation from a felsic-rich provenance.Chemical Index of Alteration was used to depict the weathering trends of all studied samples which reflect paleosedimentation under humid to sub-humid climatic conditions.