Sudden warming epochs during 42 to 28 ky bp in the Himalayan region from stable iso-tope record of sediment column from a relict lake in Goting, Garhwal, North India

Abstract

¹⁸O/¹⁶O variations of the precipitation recorded in carbonate sediments of a high-altitude Himalayan lake have been investigated by analysing samples from a varve deposit in Goting, Garhwal Himalaya. ¹⁴C ages of four samples from different depths suggest that the sedimentation in the lake started ~ 42 ky BP and continued till ~ 28 ky BP. Fluctuations in δ¹⁸O values are interpreted in terms of water-source variations. A trend showing the enrichment of δ¹⁸O values between 32 and 28 ka indicates slow cooling as one approaches the Last Glacial Maximum (LGM). There are six strong δ¹⁸O excursions (depleted ratios) coinciding with low ¹³C values at around 40.2, 38.2, 36.2, 34.2, 32.8 and 29.4 ky BP, denoting enhancement of the southwest monsoon. In addition, three positive shifts at around 40.7, 37.2 and 35.2 ky BP were observed, which indicate weakening of the southwest monsoon. Fourier analysis of the δ¹⁸O time series shows a significant ~ 740 year periodicity, similar to that reported in the Arabian Sea and South China Sea.