Influence of seabed topography on the distribution of manganese nodules and associated features in the Central Indian Basin: A study based on photographic observations

The distribution of manganese nodules and associated rock outcrops and sediment cover in the Central Indian Basin (10°–16°S, 73°–82°E), were studied from seabed photographs in relation to topographic features, categorised as the crests of seamounts and abyssal hills, their slopes, valleys and abyssal plains. The nodule coverages are high on the crests and slopes (mean coverage = 12.3 and 15.3%) and low in the valleys and plains (mean coverage = 0.3 and 1.4%). The occurrence of nodules is related to the rock outcrops and sediment cover which are in turn controlled by variations in seabed topography; rock outcrops are exposed on crests and slopes, sediment thickness increases from nil on the crests to very thin on the slopes, and from thick to very thick in the plains and valleys. High nodule concentration along the slopes and near the crests of the seamounts and abyssal hills, is a result of the availability of rock fragments as nuclei, which are derived from the rock outcrops. However, areas where nodules are absent are common in all the topographic settings.