A STUDY ON THE SIGNIFICANCE OF CLAY MINERAL BEHAVIOUR IN ESTUARY AND BEACH SEDIMENTS OF KARAIKAL COAST, EAST COAST OF INDIA

The present study was carried out in order to study about the clay minerals and their variation along the coast and the estuarine environments of Arasalar River at Karaikal. The clay minerals composition of coastal and estuarine sediments is of broad interest because of its sensitivity as an indicator of environmental change (Lanson, 1997). Clay minerals of surficial sediments have been used widely as a first order guide to the source, environment and the transport paths of fine grained sediments. The forty sediment samples were selected for the clay mineral studies in both environments. Sampling was done for two years at 3 different stations at the estuary and 2 stations (A&B) at the coast very adjoining to either end of the mouth of the river during 8 seasons starting from premonsoon-2011 to summer-2013. The sediments less than two micron size are classified as clay, have plate like crystals with layered lattice structures showing high ion exchange capacity. Owing to this property, clay minerals have an important role in the nature of sedimentation, chemistry and deposition of sediments. This simplified ion exchange process is complicated by various factors like, quality and type of cations presents in solution,pH, Eh, type of clay mineral, size etc., this process further gets intricate when river born clay comes into contact with estuarine waters. During the study period, illite was most abundant clay mineral in the sediments of the Arasalar river estuary. It varied from 70.01 to 87.39%. Along the beach, illite concentration in sediments varies over a range of 65.99 to 85.44% The higher percentage of illite was observed during monsoon and premonsoon seasons. Kaolinite+Chlorite peak reflecting the second dominant minerals over the other minerals. It ranged from 9.76 to 26.88% and the higher percentage was observed during premonsoon and summer seasons.along the coast. It is ranged from 9.96 to 28.01%. Montmorillonite content varied from 0.81 to 3.12%. It is found in higher concentration during premonsoon and monsoon seasons. Along the beach it ranged from 1.36 to 9.91%. The concentration of gibbsite varied from 0.65 to 6.03% and the higher percentage of the gibbsite was observed during postmonsoon season. Along the beach it varied from 0.73 to 4.47 %.Thus in the present study the concentration of clay minerals like illite, kaolinite, chlorite, montmorillonite, gibbsite and their seasonal variations gives a lead in deciphering the source of sediments and their interaction of Physico chemical parameters during different seasons were discussed.