18 Ka BP records of climatic changes, Bay of Bengal: Isotopic and sedimentological evidences

Abstract

Based upon the oxygen isotopic records of Globigerinoide sacculifer, the clay mineral assemblages and aridity indicator chlorite/illite (C/I) ratio, the palaeoclimatic changes during the past 18 Ka BP have been archived. The results show intense arid climate between 18 and 15 14C Ka BP, a variable climate between 15 and 13 Ka BP, and again an arid climate at 12.5 Ka BP. The negative d18O, reduced C/I and higher smectite document a humid phase culminating at 12 Ka BP. Arid climate phases are also identified at 10.3 and 11.5 Ka BP. The later event matches well with that of the ‘Younger Dryas’ event of world climate models. The beginning of the Holocene is marked by lighter d18O values (at around 9.5 Ka BP), which has been interpreted as onset of a humid phase and high freshwater influx into the bay, correlating with the world climatic event ‘mwp IB’. We also identify two more arid events at ~ 4800 and 2300– 2200 yr, hitherto unreported from the Bay of Bengal.