Sedimentation in the Indian Ocean
Based on information from more than 600 sediment cores, dredges, and available literature, several facies are distinguished in the Indian Ocean sediments: (a) terrigenous turbidites in the Ganges and Indus Cones and the Somali Abyssal Plain; (b) siliceous clay and ooze in equatorial and Antarctic regions; (c) pelagic brown and red clay in deep and central areas remote from land; (d) calcareous ooze in relatively shallow areas. In addition, we have mapped consolidated sediments on the elevated plateaus, igneous rock-outcrops on the Mid-Oceanic Ridge and manganese nodules occurring in a variety of physiographic regions. The nature and distribution of these sedimentary facies are the result of a number of factors: proximity of continents which have varying topography and climate, volcanism, oceanic productivity, water depth, physiography and various sediment dispersal mechanisms. In certain areas, the facies are modified by diagenesis through zeolitization and chertification, by ferromanganese accretion, or by carbonate cementation.
Available data suggest that the distribution and sources of the sediments characterizing some of these facies changed markedly in the geological past. For example, the siliceous clay facies of the equatorial region was either very much restricted in distribution or not present during pre-Miocene times. In pre-Miocene times the prime source for the non-biogenic detritus throughout much of the eastern Indian Ocean was in situ basalt volcanics in contrast to the varying sources since Miocene.
Mapping of sedimentary facies with varying mineralogical and physical properties is a first step towards understanding the acoustical and engineering properties of the Indian Ocean floor.
KeywordsIndian Ocean Sedimentary Facies Equatorial Indian Ocean Deccan Trap Eastern Indian Ocean
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