SEDIMENT MOVEMENT ON THE CONTINENTAL-SHELF OFF BOMBAY, INDIA

A fluorescent tracer study was carried out at a water depth of approximately 65 m on the outer continental shelf off Bombay, to decipher the sediment movement. The region is characterized by alternating bands of coarse and fine-grained sediments and also numerous NNW-SSE trending bedforms. The fluorescent tracer distribution after 1 week indicated NE-SW dispersal with a major concentration along NW and NE directions. Repeated sampling 1 year after injection showed maximum concentration of tracer in the vicinity of the release point and some concentration in the NE and SW directions. A comparison of this distribution with near-bottom current patterns in the vicinity of the site suggests that the tide-dominated currents in the presence of waves (along with a gravitative mechanism) have partly helped in the dispersal of tracers parallel to as well as transverse to the orientation of the bedforms. The marked decrease in relative concentration of fluorescent tracers over a year could be due to the apparent transport and dilution with fine-gained sediments in the east.