The paleoclimatic implication of oxygen isotopes of authigenic carbonates in loess on the Northeastern Tibetan Plateau since Last Glacial Maximum

As a significant component of the global climate system, the East Asian monsoon (EAM) is crucial in understanding general climate change. The response of sensitivity and extent of the EAM to orbital-timescale climate change remains controversial. The composition of oxygen isotopes of authigenic (pedogenic) carbonate in loess deposits from the Northeastern Tibetan Plateau was measured, which is at the modern northwestern boundary of the present-day EAM, and compared with equivalent data from northeastern China under the influence of the EAM and two selected sites in the zone under the influence of the westerlies (Bayanbulak (Xinjiang) and Kesselt (Belgium)). The data enable discussion of the paleoclimatic implication of δ¹⁸O of carbonate in loess deposits and extension (changes) of the EAM-affected area during the Last Glacial Maximum and early Holocene. The δ¹⁸O values of authigenic carbonate at the Northeastern Tibetan Plateau were close to those from the westerly climate zone, but higher than those from regions affected by the Asian monsoon during the Last Glacial Maximum and early Holocene. This indicates that precipitation moisture sources at the Northeastern Tibetan Plateau were likely not directly derived from the EAM during Last Glacial Maximum and early Holocene. In contrast, the westerlies and locally recycled or evaporated moisture were possibly the dominant influencing factors of the relatively δ¹⁸O-enriched soil water and the authigenic carbonate in Northeastern Tibetan Plateau. Further study of loess carbonate records from the Northeastern Tibetan Plateau will reveal the past climate changes in the plateau region and provide valuable clues for the interaction between the Asian monsoon and westerly climate systems.