Abstract
A study of the distribution of iron, manganese, cobalt and nickel in sediment cores from the shelf, slope and basin regions of Bornbay-Kathiawar coast of India shows that cobalt and nickel are derived from the overlying sea water as adsorbants of manganese and iron hydroxides, clay minerals, and organic matter present in the sediment. Since the cores represent differing environments, the inter-relationship and the factors governing adsorption and fixing them in the sediment vary considerably.
Mn/Fe ratio decreases uniformly with depth in the shelf sediments excepting in one core, whereas on the slope and the basin, it indicates a gain which is due to the enclosed slum and turbidite deposits. The manganese: iron ratios for (a) the shelf cores are 1 : 72; 3 : 205; and 6: 265; (b) for the slope it is 1 : 116; and (c) the basin 6: 170. The values are highest in one core. This suggests an enrichment of manganese in the shelf region and in the basin, but great mobility in the slope and parts of the shelf resulting in depletion.
Iron-cobalt and manganese-nickel are the covariants, and hence correlatable. Significantly, the organic matter in the slope sediment is inversely proportional to the amount of manganese present in the sediment. One core shows some unusuIIy high values (56 ppm cobalt and 75 ppm nickel) as against the average values of 13 and 55, respectively, for near-shore sediments (total sediment) of North Atlantic and North Pacific.
