Radiocarbon dates and Holocene sea-level change along the Cuddalore and Odinur Coast, Tamil Nadu

Five sediment cores from the tidal flats and estuaries between Cuddalore and Odinur, Tamil Nadu at similar to 50-70 cm water depth were collected to study the down core variations in organic matter, calcium carbonate content and sediment texture. Quartz, feldspar and moderately rounded to well-round, garnet-rich sand were present in all cores except core IV collected from Marakkanam. Cuddalore (cores I-III) sediments were coarse-grained and those from Odinur (core V) varied from sand to silty sand to clay. Smectite, kaolinite, illite and vermiculite occurred as clay minerals. High content of organic matter was observed in cores from Marakkanam and Odinur. Radiocarbon dates on shell, organic carbon at the base and at intervals of the cores from Marakkanam (core IV) and Odinur (core V) are 8200 +/- 230, 9170 +/- 290, 5540 +/- 430, 2700 +/- 140 yrs BP respectively. The sea-level curve presented for the Marakkanam site indicates a gradual and slow sea-level rise since 9000 to 1800 yrs BP. Data on sediment texture, mineralogy, organic matter content supplemented by radiocarbon dates indicate that the deposition of these sediments has taken place in phases since the early Holocene. Reworking of the inner shelf sediments as a result of the dropping sea-level provided the ultimate sediment source for the progradation of the present coastline.