Coastal processes of Central Tamil Nadu, India: clues from grain size studies

The sediments of the beaches along the central coast of Tamil Nadu from Pondicherry to Vedaranyam were studied for their textural variation. 108 sediment samples collected from the low-, mid-, and high-tidal zones, as well as the berms and dunes of different beach morpho-units were analysed. The study area was divided into three sectors (northern, central and southern) on the basis of prevailing energy conditions and oceanographic parameters. The poorly sorted, negatively skewed, coarser sediments of the northern sector are indicative of denudational processes taking place there. Medium-to-fine, moderately-to-well sorted, positivesymmetrically skewed sediments dominate the central sector, probably as a result of the influence of palaeo-sediments deposited by rivers from inland as well as by waves and currents from offshore. Fine, poorly sorted, positive-symmetrically skewed sediments dominate the southern sector, highlighting depositional processes. Linear Discriminant Function Analysis (LDF) of the samples indicates a shallow marine environment origin for all the three sectors. These results show that reworked sediments, submerged during the Holocene marine transgression, are being deposited on present-day beaches by waves, currents and rivers in the study area.