Depositional characteristics of recent and past washover sand sheets from Cauvery Delta Coast Tamil Nadu India

Abstract

Geological investigations of coastal sediments indicate that prehistoric tsunamis can be identified. Their characterisation has altered the knowledge of the past frequency and magnitude of tsunamis for different areas of the world. Yet there have been relatively few geological studies of modern tsunamis with virtually no direct observations of the processes associated with tsunami sediment transport and deposition. In many places on Cauvery Delta Coast of Southern India, distinct deposits of marine sand drape the landscape and overlie the muddy soils of the coastal plain. Here, using standard methods of tsunami geology, probable precedent for the 2004 tsunami in stratigraphy from the last few millennia in a mudflat terrain were identified. By reconnaissance survey, a number of pre-2004 sandsheet deposits were identified along Cauvery Delta Coast of the Tamil Nadu in Vanagiri, Karaikal, Kameshwaram and Pushpavanam showing characteristic sedimentological signatures. As the study deals mainly on finding locations for paleo-tsunami, the above mentioned areas were selected which were frequently affected by waves along the coast. Altogether 14 pits were made and samples were collected at different intervals like 1cm, 2cm and 5cm respectively to analyse washover deposits practically. Stratigraphic cross sections were assembled from correlated pits and field estimates of particle size were made; a preliminary chronology was inferred and for aminiferal analysis was done. They are compared with the characteristics observed in 26th December 2004 Indian Ocean tsunami deposits from South India. Indian Ocean tsunami has left significant sand deposits along the coastal tract of Tamil Nadu. The study of these deposits provides a better understanding of the effects of tsunami on coastlines. The evidence left by the tsunami in the coastal stratigraphy assists in providing modern analogues for the identification and interpretation of palaeo tsunami in the geologic record. newline newline newline