Evolution and Geological Significance of Holocene Emerged Shell Beds on the Southern Coastal Zone of Sri Lanka

Jinadasa Katupotha

Abstract


Assemblance of bivalve and univalve molluskan shells occur due to the eustatic and tectonic changes as well as by coastal hazards. They are a geoscientitic tool in the study of former sea-levels. Along the southern coast of Sri Lanka, the bulk of the shell valves on the "Dry Zone" between Tangalle and Bundala have been piled up by severe storm wave action on mounds, in lagoon and lake bottoms, on sand dunes and headlands. Furthermore, the shell valves of lagoon, lake and channel beds (floors of marine and brackish pools) mostly accumulated in situ due to the lowering of sea level. The deposition sequences of some shell patches of the mounds at Udamalala and on dune deposits help to infer that the valves have been discarded by early inhabitants and animals. The stratigraphy of the shell deposits had been intermittently covered by vast quantities of coral and/or shelly sand and various types of debris moved by severe monsoon waves. The colour and the materials of the shell layers show that they are subjected to local weathering conditions. Well-polished, oval-shaped stone artifacts, stone balls, human and animal bones as well as pottery fragments mixed with these shell beds are of archaeological interest.


Keywords


Coastal archaeology; sea-level change; wetlands; lagoon; submerged peneplain.

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