Micropaleontological Assemblages on December-2004 Tsunamigenic Sediments Record of Climate Variation Between Cuddalore and Nagapattinam, East Coast of India

Abstract

Ninety-nine benthic foraminiferal species belonging to 41 genera, 26 families, 17 superfamilies and 5 suborders have been identified from 84 samples which were collected from beach (23 nos), offshore (24 nos), estuaries (8 nos), inland (23 nos) and one pit sample (6 nos), between Cuddalore and Nagapattinam in the tsunami affected coastal environment. Out of 99 species, only 20 species are living ones. The following species are appreciably distributed in different stations, namely Ammonia beccarii, Elphidiumcrispum, Rosalina globularis, Asterorotaliatrispinosa and Pararotalianipponica. The total distribution of foraminifera is higher at Cuddalore and Nagapattinam whereas at Pudupettai and Samadanpettai it is noticed in the lower order. Organic matter and living species show positive relation. No relationship is observed between dead species and the organic matter, which suggests that the dead species recorded in the sediment, must have been primarily drifted/transported as empty calcareous shells. From the sand/silt/clay ratios, it is inferred that the sediments are normally sandy in nature but silty sand dominates at deeper depths. Carbonate content establishes a positive correlation with all parameters. A fluctuation of salinity values in offshore regions indicates the influx of fresh water from Colleroon river. From the overall studies of foraminiferal distribution in this region, it may be inferred that the species distribution in the offshore region is mainly derived from the inner shelf region. To observe the earlier changes in climactic condition in marine environment mainly based on information from marine sediments. The collected samples from our study area marine sediments contain a variety of foraminifera, which archive climactic information from both planktonic and benthic assemblages and in their sedimentological compositions.