Source and processes from core sediment samples off Mahanadi and Krishna rivers, western Bay of Bengal

Abstract

A total of sixteen samples representing the surface, 10 cm and 20 cm of sediment core depth between water depth of 25 m and 2600 m from the continental shelf region off Mahanadi and off Krishna were analyzed for grain size, clay minerals, total organic carbon and selected metals to understand the source and processes. The study revealed an overall decrease in sediment size from shallow to deeper water depth as well as from Mahanadi (north) to Krishna (south), indicating transportation direction. Total organic carbon content is low (less than 1 percent) and higher content was associated with finer sediment size in the samples studied. High sand content in shallow water stations off Mahanadi indicates high hydrodynamic conditions as compared to that off Krishna. High smectite content off Krishna suggests Deccan Basalt and their associated black cotton soil as their source whereas high illite content off Mahanadi suggests source belongs to Archean Proterozic Gneissic complex along with its major supply from the Himalayan region through Ganges and Brahmaputra. Ba values obtained off Mahanadi indicate the source of felsic rocks. High concentration of Fe, Mn and Ti off Krishna supports the source of basic igneous rocks. Relatively high coarse sediments, as well as high illite percentage off Mahanadi river mouth, suggests a change in land use pattern and climate in recent years.