A CORAL BASED QUATERNARY SEA LEVEL VARIABILITY RECORD IN THE PALK STRAIT OF THE INDIAN OCEAN

Exposed fossil corals found on the islands situated in the Palk Strait provide strong evidence for the sea level variability in the region and its evolution. Field investigation and subsurface investigations using ground penetration radar (GPR) and rotary drilling in Kachchathivu, Delft, Iranathivu, Eluvativu, and Punkuduthivu islands and in Jaffna Peninsula of Sri Lanka indicated that coral sequences are unconformably lie over the Miocene limestone basement. Age dating of intact corals was done using radiocarbon and U/Th techniques and their heights from the present msl was determined by leveling.

U/Th ages of corals at Kachchathivu, Iranativu and Punkuduthivu islands show that corals were grown to a minimum of 1.3 m high during 129-131 kyrs BP of the last interglacial period and 3.1 m at 107±9.3 kyrs BP. Coral growth over the Miocene limestone basement during this period has formed these island. Later these island and the coastal areas of the Jaffna Peninsular were again submerged at least by 2.1 m during the mid Holocene highstand occurred at around 5.5 kyrs BP. During this event corals again grew above the Pleistocene corals of the last interglacial period. At the end of the mid Holocene highstand sea level fell back to the present level exposing these coral islands and the coastal areas of the Jaffna peninsula.