MANGANESE MOBILIZATION FROM THE WESTERN CONTINENTAL-MARGIN OF INDIA

The Western Continental margin of India (WCMI) exhibits distinct featu res with respect to vertical distribution of manganese in sediments, T here is no significant manganese downcore variation in upper slope sed iments whereas high concentration (by an order of magnitude relative t o bottom sections) has been observed in top sediment cores for the low er slope region, Also, in the upper slope sediments, average manganese concentration is low by a factor of three compared to that (similar t o 1000 ppm) transported by the Narbada/Tapti river suspended particles , The low manganese concentration is attributed to its reductive mobil ization, Typical value of manganese flux being mobilized into overlyin g seawater fi om reducing upper slope sediments covering an area of 5 degrees Lat x 3 degrees Long is calculated to be 3x10(10) g/y, which i s nearly 10% of dissolved manganese supply to the ocean by world river s. Although calculated flux of manganese mobilized from upper slope se diments is not the highest among the values from other margin regions, yet this shows a potential source for dissolved manganese in seawater , Interestingly, the calculated carbon oxidation flux (based on mangan ese reduction rate) in the upper slope sediments is found to be less t han 1% of primary productivity and, thus it provides a limiting value of organic matter combustion, Contrary to upper slope sediments, there is no significant supply of soluble manganese to overlying seawater, which is expected due to prevailing oxidizing conditions at the sedime nt-water interface in the lower slope region.