The Romanche fracture zone sediments, equatorial Atlantic: main controls on their distribution and composition

Abstract

In the present study, the lithology, mineralogy and chemistry of sediment cores collected from different parts of the equatorial Atlantic have been investigated in order to determine the factors controlling their composition and distribution. From the sediment characteristics revealed in this study, the dominant control on the sediment composition appears to be the relative abundance of CaC03 and alumino silicate minerals. Water depth appears to play an important role in controlling the distribution of the sediments in the region. Sediments from above the CCD are dominantly calcareous oozes, whereas those sediments from below CCD are dominantly clays. It can also be seen that sediment relationship to their source areas tend to control the distribution of elements in the sediments in the region. Post-burial diagenesis has also taken place within the sedimentary column involving the shifting of Fe-Mn oxides and associated trace elements from easily reducible to more resistant phases. The element interrelations within the geochemical data indicate that the elements studied are present in biogenic, terrigenous, ultramaiic and hydrogenous components of sediments. The proportion of each of these components in the sediments is controlled largely by water depth and proximity to the source of the deposits.