Underwater geomorphology as a function of the variations in ferromanganese nodule characters in the Indian Ocean

Abstract

Ferromanganese nodules from three areas in the northern part of the Central Indian Ocean Basin have been studied. Statistical analysis shows significant variations in morphological and physical characters of nodules between the area S sub(5), which is situated on the northwestern slope of a seamount, and the other two areas, S sub(4) and S sub(6), which are away from the seamount. Surface roughness, porosity and water content are directly proportional to nodule size. Nodules from area S sub(5) which occur at shallow depth, are mostly large in size, contain rock-fragments as the nucleus, and are rich in Co and Fe and poor in Mn, Ni and Cu. In contrast, nodules from areas S sub(4) and S sub(6) occur at deeper depths, are mostly medium to small in size, contain consolidated mud as the nucleus, and are rich in Mn, Ni and Cu but poor in Fe and Co. Variation in nodule characters indicates a strong influence of seamount topography on the substantial contributions of transitional elements from seawater and sediment interstitial water to the nodules occurring in shallow and deep areas respectively