Evolution of vegetation and climate variability on the Tibetan Plateau over the past 1.74 million years

The Tibetan Plateau exerts a major influence on Asian climate, but its long-term environmental history remains largely unknown. We present a detailed record of vegetation and climate changes over the past 1.74 million years in a lake sediment core from the Zoige Basin, eastern Tibetan Plateau. Results show three intervals with different orbital- and millennial-scale features superimposed on a stepwise long-term cooling trend. The interval of 1.74–1.54 million years ago is characterized by an insolation-dominated mode with strong ~20,000-year cyclicity and quasi-absent millennial-scale signal. The interval of 1.54–0.62 million years ago represents a transitional insolation-ice mode marked by ~20,000- and ~40,000-year cycles, with superimposed millennial-scale oscillations. The past 620,000 years are characterized by an ice-driven mode with 100,000-year cyclicity and less frequent millennial-scale variability. A pronounced transition occurred 620,000 years ago, as glacial cycles intensified. These new findings reveal how the interaction of low-latitude insolation and high-latitude ice-volume forcing shaped the evolution of the Tibetan Plateau climate.publishedVersio

Phased uplift of the northeastern Tibetan Plateau inferred from a pollen record from Yinchuan Basin, northwestern China

Abstract The uplift of the Tibetan Plateau (TP) significantly affected both regional and global climates. Although there is evidence that the Tibetan Plateau experienced uplift during the Quaternary, the timing and amplitude are poorly constrained. However, the increased availability of long sedimentary records of vegetation change provides an opportunity to reconstruct the timing of the uplift. Here, we present a well-dated, high-resolution pollen record for the last 2.6 Ma from the Yinchuan Basin, which was incised by the Yellow River with its source in the northeastern Tibetan Plateau. Variations in the Artemisia/Chenopodiaceae (A/C) ratio of the reveal changes in moisture conditions in the Yinchuan Basin during glacial-interglacial cycles, as well as a gradual long-term aridification trend which is consistent with progressive global cooling. However, fluctuations in the percentages of Picea and Abies differ from those of the A/C ratio and we propose that they reflect changes in the vegetation and environment of high elevation areas. The Picea and Abies records reveal two phases of increased representation, at 2.1 and 1.2 Ma, which may indicate phases in the uplift of the northeastern Tibetan Plateau. Thus, they provide independent evidence for the timing of the uplift of the Tibetan Plateau during the Quaternary

Evolution of vegetation and climate variability on the Tibetan Plateau over the past 1.74 million years

The Tibetan Plateau exerts a major influence on Asian climate, but its long-term environmental history remains largely unknown. We present a detailed record of vegetation and climate changes over the past 1.74 million years in a lake sediment core from the Zoige Basin, eastern Tibetan Plateau. Results show three intervals with different orbital- and millennial-scale features superimposed on a stepwise long-term cooling trend. The interval of 1.74–1.54 million years ago is characterized by an insolation-dominated mode with strong ~20,000-year cyclicity and quasi-absent millennial-scale signal. The interval of 1.54–0.62 million years ago represents a transitional insolation-ice mode marked by ~20,000- and ~40,000-year cycles, with superimposed millennial-scale oscillations. The past 620,000 years are characterized by an ice-driven mode with 100,000-year cyclicity and less frequent millennial-scale variability. A pronounced transition occurred 620,000 years ago, as glacial cycles intensified. These new findings reveal how the interaction of low-latitude insolation and high-latitude ice-volume forcing shaped the evolution of the Tibetan Plateau climate

Provenance of aeolian sands in the Hetao Plain, northwestern China

Patches of aeolian sand are distributed throughout the Hetao Plain, which pose threats to farming and agriculture. Identification of the provenance of the aeolian sands may help with efforts to alleviate ecological stress in Inner Mongolia and in the paleoenvironmental interpretation of sandy sequences. This study uses geochemical data to determine the provenance of aeolian sands from the Hetao Plain. Provenance discrimination diagrams revealed that the aeolian sands were mainly derived from mixed source felsic granites and granodiorites, which have undergone weak sedimentary recycling. The chemical index of alteration and A–CN–K data indicated that the aeolian sediments were transported over a short distance. Comparison of trace element and rare earth element (REE) ratios of the aeolian sands with rock samples from potential source areas has revealed that aeolian sand deposits in the Hetao Plain were mainly derived from Sertengshan and Yellow River sediments. The Langshan and Ordos Plateau may represent additional sand sources for the Hetao Plain