We compared the stable carbon isotopic records from a loess transect of the Jiaochang in the eastern Tibetan Plateau, spanning the last ∼21,000 years, with multiproxy data for pedogenesis, including magnetic susceptibility, clay fraction, Fe d /Fe t ratio, carbonate and total organic carbon content, in order to probe the mechanisms of δ 13 C values of organic matter and Late Quaternary climate variations in the eastern Tibetan Plateau. Our results indicate that there is no simple relationship between δ 13 C of organic matter and summer monsoon variations. The change in δ 13 C values of organic matter (in accordance with the ratios of C 3 to C 4 plants) results from the interaction among temperature, aridity and atmospheric p CO 2 level. Drier climate and lower atmospheric p CO 2 level contribute to positive carbon isotopic excursion, while negative carbon isotopic excursion is the result of lower temperature and increased atmospheric p CO 2 level. Additionally, our results imply that the Tibetan monsoon may play an important role in climate system in the eastern Tibet Plateau, which specifically reflects frequently changing climate in that area. The results provide new insights into the forcing mechanisms on both the δ 13 C values of organic matter and the local climate system.
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Tang Ya (2007) studied this question.
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