|Rapid land building activity along Vedaranniyam coast and its possible implications|
The Vedaranniyam area forms a spectacular triangular shaped coast in the southeastern part of India (Figures 1 and 2). The IRS 1A satellite data (Figure 2) shows rows of beach ridges (palaeo beaches) along a coastal length of 31km from Chettipulam in the NNW to Kodiyakkarai in the SSE. The digitally processed IRS 1A image (band 2, density sliced data) of 1990 shows offshore sand bars upto 27km southeast of Vedaranniyam nose (Point Calimere) inside the sea (2, Figure 3).
Shell samples were collected from 1.2 to 3m depth from four beach ridge complexes from NNW to SSE, at Chettipulam, Maranganallur, Tettagudi and Kodi- yakkarai which are respectively 32km, 22km, 19km and 1km from the present day coast (Figure 2).
Existence of beach ridges upto Chettipulam indicates that the sea might have been upto Chettipulam and regressed to Kodiyakkarai in the recent past. 14C dating of beach ridge at Chettipulam (1, Figure2) shows an age of 6085 223 y.B.P., at Maranganallur (2, Figure 2) 5646 223 y.B.P., Tettagudi (3, Figure 2) 3570+/-205y.B.P. and Kodiyakkarai (5, Figure 2) 1020+/-80y.B.P. The Veda-raneswarar temple located over the beach ridge at Vedaranniyam (4, Figure 2) suggests an approximate age of 1300y.B.P. (7th century A.D) to the ridge here1. The density slicing of IRS 1A band 2 data shows that the offshore bars have developed up to 27km inside the sea (2, Figure 3), and as this data was obtained in 1990, it is reasonable to assume the same age to these offshore bars.
The 14C dates evaluated for the beach ridges show that the sea has gradually regressed due to the rapid accumulation of sediments and the development of cuspate landforms in between Chettipulam and Kodiyakkarai during these 6000 years. Our data has shown that the sea has regressed by 10km in 439 years from Chettipulam to Maranganallur, by 4km in 2076 years from Maranganallur to Tettagudi, by 8km in 2270 years from Tettagudi to Vedaranniyam, by 8km in 220 years from Vedaranniyam to Kodiyakkarai and by 28km in 1020 years from Kodiyakkarai to present day offshore bars. These show that the beach ridges have grown at the approximate rate of 23m/y (metres/year) from Chettipulam to Maranganallur, 2m/y from Maranganallur to Tettagudi, 3.5m/y from Tettagudi to Vedaranniyam, 36m/y from Vedaranniyam to Kodiyakkarai, 27.5m/y from Kodiyakkarai to the recently developed offshore bars of 1990. The above observations show that there is no strict linear relation between the rate of sediment accretion and the time period. Infact, under such dynamic coastal regimes, linear relationship cannot be expected because of varying degrees and duration of the fluvial and physical oceanographic processes. But, however in average (excluding Maranganallur to Tettagudi and Tettagudi to Vedaranniyam) the land building activity is around 29m/y and if this accretion rates maintained Veda- ranniyam nose will get connected to Jaffna peninsula, just 12km from the offshore bars (2, Figure 3), in another 400 years. Regionally from Chettipulam to present day offshore bars, the land has grown to a distance of 58km in 6085 years, at an average rate of 10m/y. At this rate the offshore bars will provide a land connection with Jaffna peninsula in another 1200 years. The graphical projection of the locations of the beach ridges versus their ages has shown a coarse linear relationship indicating that the Veda- ranniyam nose will get connected with Jaffna peninsula in another 2400 years (Figure 4).
The sediment building activity due to littoral currents seems to be very rapid in this area with the rate of 29m/y and hence there is a possibility for such land building/connection in another 400 years. Ramasamy and Balaji2 on the basis of satellite imagery interpretation have identified that the Mio-Pliocene sandstone of Vedaranniyam area is undergoing an upliftment in post Mio-Pliocene period. Ramasamy et al.3 have observed an anticlockwise rotational migration of Cauvery river in the area north and northwest of Chettipulam-Kodiyakkarai during 2300-750y.B.P. and attributed this to the ongoing upliftment of Mio-Pliocene sandstone and the resultant sediment accretion in Chettipulam-Kodiyakkarai area. Rama- samy and Karthikeyan4 have observed further geomorphic and hydrogeochemical anomalies favouring ongoing land emergence in Vedaranniyam area. It is obvious therefore, that the tectonic upliftment has contributed substantially for such sediment accretion brought by littoral currents in Kodiyakkarai-Jaffna peninsular sector and hence it can be confidently said that Vedaranniyam land segment will get connected with Jaffna peninsula ultimately.
1.Venkatarajulu, S., PhD thesis, Bharathidasan University, Tiruchirapalli, (unpubl.), 1994, p. 160.
2.Ramasamy, SM. and Balaji, S., Int. J . Remote Sensing, 1995, 4, 2800-2832.
3.Ramasamy, SM., Balaji, S., Venkata- subramanian, V. and Paul, M. A., INTERFACE, Bull. NRSA Data Centre, 1995, 6(4), 5-6.
4.Ramasamy, SM. and Karthikeyan, N., Geo Carto Int. J., 1997 (in press).
M. A. PAUL
M. G. YADAVA
A. R. NAIR
U. K. SINHA
T. B. JOSEPH
Centre for Remote Sensing,
Tiruchirapalli 620024, India
<187>Radio Carbon Dating Laboratory,
Physical Research Laboratory,
Ahmedabad 380009, India
Bhaba Atomic Research Centre,
Mumbai 400085, India
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