The coupling of Orbulina universa diameter with the warming and cooling events in the Arabian Sea over the past 40,000 years

A 40 ky record of variations in the average diameter of Orbulina universa from a 5.4 m core (SK-322) in the Arabian Sea, off Goa, India has been analysed in this study. The chronology of the upper 1.00 m of the core was documented by AMS radiocarbon dates. Fifty specimens of O. universa were hand-picked from each of the 50 subsamples. In all, 2500 specimens were measured for their diameter. Downcore variations in the average diameter of O. universa were in excellent agreement with the curve representing the Iberian Margin temperature index, with the peak representing the Bolling-Allerod transition and the troughs reflecting Heinrich Event I and Younger Dryas. The lower part of the core examined in this study (between 58 and 100 cm), which is the equivalent of 30,000-40,000 years BP, is marked by closely spaced peaks and troughs that are interpreted as representing the Dansgaard-Oeschger cycles that were dominant in the Northern Hemisphere between 60,000 and 30,000 years BP.