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Four short core samples were collected from the creek, estuarine regions of southeast (SE) coast of India affected by the 2004 Asian Tsunami. The study is aimed to signify the importance of ostracoda species in identifying major natural events (e.g. Tsunamis) in the coastal regions. The presence of many marine ostracoda species in the beach areas and the comparative studies with earlier reports from SE coast indicate that these species were brought by the high-energy tsunami waves. The depositional feature of ostracoda species in the beach and estuarine region also infers on the nature and force of tsunami waves in a particular region. The results clearly support that microfossils can be used to identify the major natural events close to coastal regions.

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Palaeoclimate, palaeoecological and palaeoshoreline studies were carried out for a 2.5 m deep sediment core deposited since ∼3700 yrs BP in the central part of Pichavaram mangrove wetland, Cauvery river delta. Presently, the study area is dominated by Avicennia officinalis, A. marina and Suaeda sp. with fringes of Rhizophora sp. along the backwater channel. Based on sedimentology, palynological and thecamoebian analysis, it is inferred that since 2100 yrs BP the climate amelioration took place from warm and humid with strengthened monsoon to a dry and arid climate coupled with weakened monsoon condition inducing changes in ecology vulnerable for mangroves. Consequently, the vegetation too evolved from moist deciduous/evergreen forest to mixed deciduous forest and a reduction in mangrove diversity. The qualitative and quantitative study show a decline in the mangroves since the last millennium which may be attributed to the increased salinity along with enhanced anthropogenic activities in Pichavaram estuary. This is reflected by the dominance of salt tolerant mangrove associates since the last millennium.

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An attempt has been made to establish the sediment-ostracode relationship, in the gulf of Mannar, off Tuticorin, south east coast of India. 48 sediment samples were collected from 12 sampling stations. Twelve bottom sediment samples were collected once in three months, for a period of one year, so as to represent the four seasons (winter, summer, southwest Monsoon and northeast Monsoon). Calcium carbonate and organic matter content of each sample were correlated against the ostracode population recovered in the respective sample. An increase in the CaCO3 percentage and a decrease in the organic matter content generally favor a higher population size.