EVIDENCES OF CLIMATIC VARIATIONS DURING LATE PLEISTOCENE-HOLOCENE IN THE EASTERN BAY OF BENGAL

Based upon the variations of clay minerals, sediment texture, heavy mi neral assemblage and Th-230 excess in the Late Pleistocene sediments o f a hemipelagic core from the eastern Bay of Bengal (2713 m water dept h), 35 cm and 73-78 cm levels are assigned as Holocene-Pleistocene Bou ndary and Last Glacial Maxima (LGM) respectively. Two dominant arid ph ases and weak monsoon around LGM (73-110 cm) and at Holocene-Pleistoce ne boundary are identified from high concentration of chlorite, C/I ra tio maxima (aridity reflector), decrease in characteristic clay minera l suites of humid climate, i.e. smectite and illite and a low K/C rati o. The intensity of monsoon between LGM and 15 ky-1 has been cyclic, a nd enhanced thereafter until the beginning of Holocene as deduced from high smectite, reduced chlorite and higher K/C ratio of sediments in 40-73 cm section (LGM-Early Holocene). Between 35 and 40 cm, at the be ginning of Holocene, a significant reversal in the climate from humid to arid, and associated decrease in the monsoon intensity is interpret ed. Clay mineral assemblage (high content of smectite, low chlorite) a nd their ratios, sediment texture and absence of heavy minerals betwee n 0 and 35 cm, reflect the prevalence of stronger monsoon since 10 ky- 1 BP. Angularity of quartz, characteristics of heavy and clay mineral suites and presence of glass shards have been utilized to determine th e source of the sediments to this part of the Bay of Bengal.