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A. L. Paropkari ¹, Ch. M. Rao ¹, P. S. N. Murty ¹

Affiliations
1 National Institute of Oceanography, Dona Paula 403004, Goa, IN

Abstract

Total phosphate in the sediments ranges from 0.15 to 0.29% in the bulk samples and from 0.09 to 0.23% in the acid soluble fractions of the samples. There was no appreciable variation in the phosphate within the Gulf and no significant relation was observed between phosphate content and texture of the sediments. Invariably higher concentrations of phosphate were associated with the acid soluble fractions as compared to the acid insoluble fractions. The contributions made by the acid insoluble fractions to the phosphate concentration in the bulk samples was probably through the detrital minerals with which it might be associated, while the contributions made by the acid soluble fraction was probably in the form of adsorbed phosphate than in association with the carbonate phase.

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CH. M. Rao ¹, P. S. N. Murty ¹

Affiliations
1 National Institute of Oceanography, Dona Paula 403004, IN

Abstract

The modern sediments accumulating on the western continental margin of India between 17° and 13° latitude are composed predominantly of terrigenous material in the inner shelf with moderate organic carbon content (< 3%), carbonate sediments in the outer shelf with low organic carbon content (< 1%) and organic carbon rich (upto 12%) carbonate sediments in the slope region. The bulk and partition geochemistry of the surface sediments reflect the complex intermixture of several sedimentary components (lithogenic, authigenic and biogenic) and enable the identification of geochemical processes that are responsible for the incorporation of elements into the sediments. The elemental concentrations are found to be related to the distribution of three major components i.e, terrigenous debris (Si, Al,Ti, Fe, Mn, Cu), authigenic Calcium Carbonate (Sr, P) and organic carbon (P, Ni, Zn).

Keywords

Geochemistry, Marine Geology, West Coast of India, Continental Margin Sediments.

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V. Purnachandra Rao ¹, Ch. M. Rao ¹, A. Mascarenhas ¹, K. Mohan Rao ², N. P. C. Reddy ², H. C. Das ³

Affiliations
1 National Institute of Oceanography, Dona Paula 403 004, Goa, IN
2 National Institute of Oceanography, Regional Centre, 52, Kirlampudi, Layout, Visakhapatnam 530 023, IN
3 Oil India Limited, Duliajan, Assam 786 602, IN

Abstract

Sedimentological and geochemical investigations of the sediments in a core from the eastern continental margin of India, at a water depth of 1200m, revealed two distinct sediment types. The Late Pleistocene sediments are greyish-black in colour and consist of mud turbidites in the lower part and dolostone breccia in the upper part. They also consist of illite and chlorite-rich clay minerals with high organic carbon and sulfur. Organic matter is of dispersed nature. These are similar to black shales and are apparently formed by rapid burial of terrigenous organic matter by turbidites with intermittent reducing conditions during lowered sealeveIs. Dolostone fragments appear to have been transported by mass movement processes during the terminal pleistocene. The Holocene sediments: are moderate yellowish-brown in colour and with detrital vivianite nodules at the base. These sediments are clayey with mont-morillonite-rich, illite-poor clay minerals, lower organic carbon and sulfur contents and ferruginised pyrite grains, deposited under oxidising conditions. The marked changes in the sedimentary environments are attributed to climate and sealevel changes during Pleistocene and Holocene.

Keywords

Environment, Pleistocene, Holocene, Black Shales, Off Penner River, Continental Margin.

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Ch. M. Rao ¹, P. S. Rao ¹, K. A. Kamesh Raju ¹

Affiliations
1 National Institute of Oceanography, Dona Paula, Goa - 403 004, IN

Abstract

No Abstract.

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