Distribution and composition of verdine and glaucony facies from the sediments of the western continental margin of India
Abstract
Investigations on green grains from sediments of the western continental margin of India, between Ratnagiri and Cape Comorin, (water depth 37-330 m) indicate the presence of verdine and glaucony facies. Verdine facies occurs over an area of about 100,000 km sup(2), representing the largest sedimentary basin in the world associated with low fluvial input. Green grains occur as irregular grains, fecal pellets, and infillings/internal molds of microfossils. They are abundant on the shelf off river mouths and their distribution varies with sediment type. Grains vary from dark green to pale green or brownish green. Green grains studied here are a mixture of predominant authigenic green clay and detrital clay minerals and are altered. Both phyllite C and suspected phyllite V- (verdine mineral minerals) associated green grains occur on the continental shelf (between 37 m and 100 m), the former being associated with the transition zone between inner and outer shelf and the latter with relict sands and reefs on the outer shelf. The distribution of verdine and glaucony facies on the southwestern margin of India is different from those of the distribution along the east coast of India, Senegal, and French Guiana margins, suggesting different paleogeography and subsidence history of the western Indian margin during the Late Quaternary
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