Distribution and sources of sedimentary organic matter in a tropical estuary, south west coast of India (Cochin estuary): A baseline study

► We report δ13C and δ15N values of sedimentary organic matter from the Cochin estuary. ► δ13C and δ15N values ranged from −27.5‰ to −21.7‰ and δ15N 3.1-6.7‰ respectively. ► Organic matter is found to be mixture terrestrial and marine derived materials. ► The δ15N values displayed a complex behavior in the study region. ► The fraction of terrestrial derived organic matter was estimated.