Past 20,000-year history of Himalayan aridity: Evidence from oxygen isotope records in the Bay of Bengal
Late Quaternary climate history of the Himalayas is inferred from sea surface salinity (SSS) changes determined from the oxygen isotope in planktonic foraminifers, in a turbidity-free, 14C-dated core from the Bay of Bengal. The heaviest d18O incursion (– 0.9 and – 0.44‰ for Globigerinoides ruber and G. sacculifer respectively) between 20 and 15 Ka BP reveals that the Himalayas was intensively glaciated with minimum fluvial discharge until 15 Ka BP. During the initial phase of deglaciation between 15 and 12.5 Ka BP, the climate was unstable. The deglaciation intensified after 12.5 Ka BP, and culminated at about 11 Ka BP with a fluvial pulse. The heavier concordant incursions of d18O in both the species indicate that Himalayan aridity and associated glaciation at 10.5 Ka BP was again enhanced to the magnitude of the Last Glacial Maxima. The beginning of Holocene (~ 9.5 Ka BP) is characterized by excessive lighter d18O values due to high fluvial discharge attributed to intensified monsoon regime that persisted throughout the Early Holocene. During Mid–Upper Holocene, the Himalayas experienced at least two significant episodes of aridity and intensified glaciation at 5–4.3 and ~ 2 Ka BP.
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