MIDDLE AND LATE HOLOCENE SEA-LEVEL CHANGES IN AND AROUND PULICAT LAGOON, BAY-OF-BENGAL, INDIA

The Pulicat Lagoon adjoining the Bay of Bengal is underlain by marine sand, silt and clay beds showing middle and late Holocene cycles of de siccation along its western fringe. Within the lagoonal sequence there are bivalve-rich layers (C-14 ages 3100-2320 yr B.P.) at depth of 1.1 0-1.65 m below the surface in the central part. The marine sediments l ie over a substrate of marshy peat dated at 6650 yr B.P. Within the pr esently dried parts of the lagoon the sediment record is interrupted d ue to frequent regressions. Cycles of desiccation and accompanying sea level fall could also account for the development of sand dunes over the western, central and eastern borders of the lagoon, including the Sriharikota spit, which developed in five stages. The rate of net sedi ment accumulation in the lagoon varies from less than 1 mm/a along the western half to 2.5 mm/a at its eastern margin.