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A. T. Rao ¹, C. V. Raman ¹

Affiliations
1 Department of Geology, Andhra University, Waltair 530003, IN

Abstract

Charnockites in parts of the Eastern Ghats show indications of sulphide mineralisation. Pyrrhotite, chalcopyrite and galena have formed in paragenetic sequence replacing blue quartz, black feldspars, hypersthene and pink garnet of the charnockites near Kondapalli in Andhra Pradesh.

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A. T. Rao ¹, C. V. Raman ¹

Affiliations
1 Department of Geology, Andhra University, Waltair, IN

Abstract

Vemparala in northernmost Precambrian Nellore schist belt is made up of banded quartz-magnetite rocks, quartzites, pyroxene granulites, gabbros and granites. These were subjected to folding and refolding resulting in F₁, F₂, F₃ folds. Spinel-bronzite pyroxenites were structurally emplaced along the crests of F₂ folds and are the first known occurrences in Nellore Precambrian belt.

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C. V. Raman ¹, A. T. Rao ¹

Affiliations
1 Department of Geology, Andhra University, Waltair 530003, IN

Abstract

The red sediments of Recent age confined to the slopes of hill ranges and along the coast of Visakhapatnam and Bhimunipatnam are classified into inland and coastal red sediments. The textural analysis reveals that the inland red sediments are poorly sorted with negative skewness, and the coastal red sediments are better sorted and positively skewed. Beach samples are well sorted Showing both positive and negative skewness. In the light of skewness patterns it is concluded that the coastal red sediments were laid down in a depositional environment, whereas inland red sediments belong to an erosional or non-depositional environment and further that these clastic red sediments are immature and have formed under a fluvial environment.

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C. V. Raman ¹, K. S. N. Reddy ¹

Affiliations
1 Department of Geology, Andhra University, Visakhapatnam - 530 003, IN

Abstract

Textural distribution patterns of seafloor sediments from the Mahanadi-Nagavali shelf, northwest Bay of Bengal, are used to evolve a model for the regional sediment-dispersal system. Mean size trends, standard deviation, skewness and correlation of negative skewness with silt/Clay ratios reveal certain patterns, each being specific to an area(s) of shelf. Sediment distribution patterns show that the near shore environment is occupied by sand and clayey sand, while the inner and middle shelf regions are covered by sandy silt, silty calcareous sand, silty clay, silty sand and sand-Silt-Clay. The outer shelf is largely covered by clayey silt. Relict carbonate deposits are preserved on the outer shelf at ∼100 m off Rushikulya to Baruva. Palimpsest sediments cover the Sonapurapeta-Bavanapadu shelf at depths of 0-60 m.

Mud dispersal in the study area offshore is caused by transport components along and across the shelf. The Mahanadi-Devi River system is the principal source of sediment for the Mahanadi-Nagavali shelf. The Nagavali and Vamsadhara rivers are a minor source of sediment towards the southern part of the shelf, and their detrital inputs are largely deposited on the shelf adjacent to the river mouths. Sediments in the study area are transported and advected southward (bottom nepheloid layers ?). The Mahanadi-Nagavali shelf response to the present hydraulic regime is recorded in the modern sand facies and the offshore mud facies, particularly the silty clays.

Keywords

Continental Shelf, Sediment Dispersal, Grain Size, Relict Sands, Bay of Bengal, India.

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C. V. Raman ¹

Affiliations
1 Department of Geology, Andhra University, Visakhapatnam - 530 003, IN

Abstract

No Abstract.

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