Echo characters of the continental margin, western Bay of Bengal, India

Abstract

An echo character study of about 35,000 km length of 3.5 kHz echograms, recorded from the continental shelf, slope and rise domains in the western Bay of Bengal, reveals twenty echo types. Based on their distribution, the analysis of sediment cores, and comparison with the similar echo types reported from Atlantic continental margin, the echoes are interpreted to reflect variation in sediments produced by different processes. The distribution of various echo types are significantly different within each physiographic province. Shallow marine processes have influenced the continental shelf off non-deltaic areas whereas fluvio-deltaic processes dominate areas off deltas. Deposits formed by mass wasting dominate the continental slope off Puri-Machilipatnam and off Pondicherry where the sea floor is eroded and gullied by slides, slumps and debris flows. The deposits developed under the influence of combined processes are most widespread on the continental rise south of Kakinada. The rest of the continental rise, the continental slope off Nizampatnam Bay and Cauvery River, and the Bengal Fan are influenced by turbidity currents. The Bengal Fan is also affected by mass wasting.