A study on pre- and post-tsunami shallow deposits off SE coast of India from the 2004 Indian Ocean tsunami: a geochemical approach

A study was made on samples from one core collected immediately after the December 2004 Asian tsunami to know the geochemical nature of the offshore tsunami sediments. The core sample was analyzed for sediment grain size, CaCO₃, organic carbon (OC) and major elements (SiO₂, TiO₂, Al₂O₃, Fe₂O₃, CaO, MgO, Na₂O, K₂O, P₂O₅, MnO). The results indicate that the core sample can be divided into two parts: (1) upper 0–25 cm, interpreted to be deposited after tsunami (AT), and (2) lower 25–45 cm, interpreted as before tsunami (BT) as evidenced by the sandy nature AT with fluctuating CaCO₃ contents. The AT part is devoid of OC suggesting that the sediment could have been transported to deeper regions along with the finer particles. Major elements such as SiO₂, TiO₂, CaO indicate high values than the other elements in AT part than in the BT part. The BT part contains Al rich alluvium mud associated with finer mud and organic particles. An analysis of the correlation matrix indicates the possible source of elements and transport of heavy minerals in the AT part than the BT part. The overall results suggest that the sediments could possibly have two different origins.