Asian monsoon rainfall variation during the Pliocene forced by global temperature change

摘要

The Asian monsoon variations under global temperature changes during the Pliocene are still debated. Here we use a sedimentary record of phytoliths (plant silica) from the Weihe Basin, central China, to explore the history of Csub4/sub grasses and quantitatively reconstruct the Asian monsoon climate since the late Miocene. Our results show that Csub4/sub grasses have been a dominant grassland component since ~11.0?Ma. A subsequent marked decrease in warm- and humid-adapted Csub4/sub grasses and an increase in cool- and dry-adapted Csub3/sub grasses occurred in the Pliocene, ~4.0?Ma; the phytolith-based quantitative reconstruction of mean annual precipitation marked a?decrease from 800~1673?mm to 443~900?mm, indicating a reduction in Asian monsoon rainfall in the Pliocene. Our newly obtained records conflict with the hypothesis that the growth of the Tibetan Plateau strengthened the Asian monsoon rainfall. Nevertheless, they emphasize the importance of global temperature as a determinant of Pliocene Asian monsoon variations.