Kapila Dahanayake

Recent- and Paleo-tsunami Sediments of Sri Lanka: Sedimentology, Micropaleontology and 14c Dating Kapila Dahanayake

Authentic tsunami sediments collected from a previously empty bottle and several coastal localities were identified as brownish silty fine sand with a characteristic grain size distribution and an assemblage of planktonic and benthic microfossils. e.g forams. Influenced by references in Sri Lankan ancient texts to occurrences of tsunamis a search was undertaken for paleotsunami sediments in selected coastal villages of Peraliya and Denuwala. In boreholes and well cuttings of such locations we recognize two paleotsunami horizons at 30 and 75 cm respectively below the present ground surface each consisting of brownish silty fine sand with microfossils that remarkably resembled those found in the recently deposited uncontaminated tsunami sediment. The 14C dating of different tsunami sediments gave anomalous ages. However their C/N ratios indicated marine origins. The book highlights diagnostic criteria to identify authentic past and recent tsunami sediments and discusses the challenges of 14C dating tsunami sediments. It is a landmark publication of interest to geologists, paleontologists, archaeologists and in modeling and dating tsunamis