Palynological and stable isotopic study of palaeoenvironmental changes on the northeastern Tibetan plateau in the last 30,000 years

Abstract

The Tibetan Plateau is important in influencing the atmospheric circulation of the Northern Hemisphere. However, only a few continuous palaeoclimate records are available. Here, we present a 30,000 year pollen and carbon stable-isotope record of two lacustrine sections from the Zoigê Plateau on the northeastern Tibetan Plateau. The pollen spectra show that the territorial palaeovegetational evolution experienced 7 stages in the following order: (1) 30.0 (?)–26.0 kyr B.P., alpine desert and desert–grassland vegetation; (2) 26.0–18.0 kyr B.P., grassland and alpine meadow vegetation; (3) 18.0–14.2 kyr B.P., alpine desert; (4) 14.2–10.0 kyr B.P., grasslands and meadows with islet forests; (5) 10.0–9.4 kyr B.P., marsh and meadow vegetation; (6) 9.4–4.0 kyr B.P., dark conifer islet and marsh; and finally (7) 4.0 kyr B.P.–present, marsh and subalpine meadows with scattered islets of dark conifer. The palaeoclimate was inferred from these variations in palaeovegetation, and in particular, the variation in the last 12,000 years was confirmed by the δ 13C curve of the No. 2 pit section. Major post-glacial climatic events are clearly identified in the two study sequences, including the Late Glacial series of Bölling, Alleröd, Old Dryas and Younger Dryas, and the Holocene Optimum. The climate records in the two sequences also indicate a long-term trend towards aridity in the study area.