Geological Significance of Marine Molluskan Beds: Evidence from Southern Coastal Zone of Sri Lanka

Abstract

Mollusks are invertebrate animals that live in brackish water or marine habitats. The diversity and complexity of these habitats are due to winds, waves, tides, bottom features, daytime illumination, geologic origin of shoreline and ecologic conditions ofthe oceans. Assembly ofbivalve and univalve mollusks occur due to the eustatic changes and the prevalence ofcoastal hazards. Stratigraphic sequences ofshell beds along the southern coast between Kalametiya Kalapuwa (lagoon) and Bundala Lewaya (salt-pan) clearly indicate that shells have been piled up together with stone artifacts, pieces of pottery, human bones and other animal bones. These were caused by severe storm wave action on mounds in lagoon and lake bottoms, on sand dunes and headlands. The present study shows that the shell valves of lagoon, lake and channel beds (floors of marine and brackish pools) mostly accumulated in situ consequent to the lowering of sea level between 5030 - 4390 and 3930 - 3290y B.P.