A note on geochemistry of surface sediments from Krishna-Godavari basin, East Coast of India

Abstract

A closely spaced 75 surface sediments drawn from ‘Gas Hydrate` Project taken up by National Institute of Oceanography on a regional scale from the Krishna-Godavari Basin (Latitude I5 degrees 35 minutes to 16 degrees 20 minutes N; Longitude 81 degrees 40 minutes to 82 degrees 30 minutes E) are analysed for texture, major, and some trace and rare earth elements to understand their source and provenance. Water depth in the study area varies between 300 to 2000 m and there is a WNW-ESE trending sedimentary ridge in the southwestern part of basin. Sediments are mostly silty clay in nature. Ti - bearing minerals such as titanite and pyrophanitc are evident by the strong positive correlation between Ti and Ca (r = 0.89) and Ti and Mn (r =0.67) respectively. An independent behaviour of Zr suggests occurrence of zircon mineral. The strong positive correlation among Al, Fc, Mg and K (r = 0.68 to 0.90) suggests their association with clay. The average total REE (IREE 176 plus or minus 13 ppm) abundance is similar to that of average shale with a flat shale- normalized REE pattern suggest a terrigenous source. High concentration of Fe (6.45+0.43%), Ti (0.82+0.07%), V (192 plus or minus 23 ppm), Cr (128 plus or minus 13 ppm) and Zr (I59 plus or minus I9 ppm) and presence of smectite as a major clay mineral suggest that Peninsular Godavari River has sediment influx from source rocks of Eastern India mainly Deccan Trap, Precambrian and Dharwar formation. Further, it confirms that the role of Ganges-Brahmaputra River sediments to the basin appears to be small compared to the Peninsular rivers.