QUARTZ AND FELDSPAR DISTRIBUTION IN CONTINENTAL-SHELF SEDIMENTS OF EAST-COAST OF INDIA

Coarse fractions of 57 sediment samples from the eastern continental shelf of India between the Hoogly mouth and Krishna mouth have been analysed for quartz and feldspar distribution. Highest concentrations (80-90%) of quartz are in the sediments between Kalingapatnam and Chilka lake and in the area north of the Mahanadi. It is lowest (50-60%) in the sediments off the Krishna and Godavari and in the outer continental shelf off Visakhapatnam. Plagioclase feldspar concentrations are high (20-40%) in the clayey silt sediments off the Krishna and Godavari and low (< 10%) in the sandy sediments which occur in the northern part. Alkali feldspar to quartz ratios range from 0.05 to 0.27 in the inner shelf and 0.4 to 0.9 in the outer shelf sediments off Visakhapatnam. Variations in the distribution of quartz and feldspar have been attributed to coastal geology and rock formations in the drainage basins of the rivers. It is further suggested that the feldspar quantity cannot be regarded as a climatic indicator in all the regions.