Characteristics of 2004 tsunami deposits of the northern Tamil Nadu coast, southeastern India

Abstract

The 2004 Indian Ocean tsunami left significant sand deposits along the coastal tract of southeast India (Tamil Nadu state). These deposits serve as a benchmark to understand the effects of present day tsunami on the coastline. Additionally, the geological signatures of tsunami in the coastal stratigraphy can assist in providing modern analogs for identification and interpretation of ancient tsunami. This article presents the field observations of tsunami deposits, their internal stratigraphy and foraminiferal distribution, all of which varied from north to south depending upon coastal geomorphology, near shore bathymetry and sediment sources. In a few places, the tsunami deposits have been reworked due to subsequent events that caused modification in the internal stratigraphy. The tsunami deposits of the northern Tamil Nadu coast comprise at least 50% or more reworked foraminiferal specimens, indicating that the tsunami sediments may have been derived from a paleostrandline from a water depth of at least 45 m Key words: 2004 tsunami, geomorphology, foraminifera, sand deposits, southeast coast of India. Resumen El tsunami de 2004 en el Océano Índico acumuló una capa de sedimentos gruesos (depósitos de arena) a lo largo de la costa sureste de la India, particularmente en el estado de Tamil Nadu. Esos depósitos sedimentarios sirven como referencia para entender los efectos de tsunamis actuales en las zonas costeras. Además, las características geológicas de los depósitos de tsunami actuales en la estratigrafía costera asisten en identificación e interpretación de los tsunamis antiguos. En este artículo presentamos las observaciones del campo sobre los depósitos de tsunami, su estratigrafía interna y distribución de foraminíferos según varía de norte a sur, dependiendo de la geomorfología costera, de la batimetría somera, y de la proveniencia de los sedimentos. En algunas localidades, la estratigrafía interna de los depósitos fue perturbada debido a eventos subsiguientes. Los depósitos de tsunami de 2004 en la costa norte de Tamil Nadu constituyen al menos 50% o más de las foraminíferas retransportadas, lo cual indica que los sedimentos de tsunami fueron derivados de un paleo-costa, actualmente ubicado a una profundidad de al menos 45 m.

Ostracoda as an aid in identifying 2004 tsunami sediments: a report from SE coast of India

“…Paris et al 2007). The above inference is also in accordance with earlier report in the same area by Srinivasalu et al (2009a), indicating that the tsunami layers are seen above the organic layers in many places.…”

“…The inference is also very well documented by the large number of broken carapace valves signifying high-energy tsunami waves in the southern part of the study area. The above high energy activity is very well supported by the huge tsunami deposits in many places (Srinivasalu et al , 2009a.…”

“…Studies related to the recent 2004 Asian Tsunami have been made by several authors along southeast coast of India on various geological aspects (Srinivasalu et al , 2009aYeh et al 2006). The transport of foraminiferal species from deeper regions to the coastal regions in other areas has been reported by Dominey-Howes et al (1999) (Western Australia); Hindson et al (1999) (Algrave, Portugal); Fujiwara et al (2000) (Southern Kanto region, Pacific coast of Central Japan); Luque et al (2002) (Bay of Cadiz, Spain); Ruiz et al (2004) (Doñana National Park, SW Spain); Nagendra et al (2005) (SE coast of India); Hussain et al (2006), Malik et al (2006) (Andaman Islands, Indian Ocean); Nigam and Chaturvedi (2006) (NE Arabian sea); Hawkes et al (2007), Jankaew et al (2008) (Malaysia-Thailand Peninsula) and Smedile et al (2007) (Eastern Sicily, Italy).…”

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

“…In addition, the southern part of Cauvery basin (part of Nagapattinam and Karikal Town) in the peninsular shield is underlain by rocks of Archean age and the coastal tract is covered by younger alluvium and coastal sands (Mohanachandran and Subramanian 1990). The study area also witnessed maximum backwash of sediments from land during/after the three major tsunami waves that struck the coastal region (Srinivasalu et al 2009). 2.1 Sample collection and methodology adopted Several core samples were collected immediately (1st week of January, 2005) during a cruise in CRV Sagar Paschimi after the December 2004 Asian tsunami event.…”

“…The sandy nature is due to the high Tsunami waves and intense current activity. The result is that the finer particles remain in suspension (as evidenced by the backwash process due to the three large Tsunami waves: Srinivasalu et al 2009) for a fairly long time and are progressively removed to deeper regions by the tidal currents.…”