The present study was carried out in order to study about the clay minerals and their interaction in the coastal environments of Arasalar river estuary at Karaikal. The clay minerals composition of coastal and estuarine sediments is of broad interest because ofits sensitivity as an indicator of environmental change (Lanson, 1997). Clay minerals of surficial sediments have been used widely as afirst order guideto the source, environment and the transportpaths of fine grained sediments. Sampling was done for two years at 3 different stations 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 withlayeredlattice structures showinghighionexchange capacity.Owingto this property, clay minerals have animportant role in the nature of sedimentation, chemistry and deposition of sediments. This simplified ion exchange process is complicated by various factors like, quality and typeof 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 studyperiod, illite was most abundant clay mineral in the sediments ofthe Arasalar riverestuary.It varied from70.01 to 87.39%. The higher percentageofillite was observedduring monsoon and premonsoonseasons. Kaolinite+Chlorite peak reflecting the second dominant minerals over the other minerals.Itranged from 9.76 to26.88% and the higher percentage was observed during premonsoonand summer seasons. Montmorillonite content varied from 0.81 to 3.12%. It is found in higher concentration during premonsoon and monsoon seasons. The concentration gibbsite varied from0.65 to 6.03% and the higher percentage ofthe gibbsite was observed duringpostmonsoon season. Thus in the present study the concentration of clay mineralslike illite, kaolinite, chlorite, montmorillonite, gibbsite and their seasonal variations givesa lead in deciphering the source ofsedimentsand their interaction of Physico chemical parameters during different seasons were discussed.
