Late Quaternary pollen records from the Yangtze River Delta, East China, and its implications for the Asian monsoon evolution

摘要

Compiled pollen records derived from four cores (ZK004, ZK005, SZ03, and SZ04, respectively) were established to reveal the last 800 thousand years (ka) climate change and its driving forces in the Yangtze River Delta, East China. The percentages of the herbaceous taxa (Poaceae, Artemisia, Asteraceae, Chenopodiaceae, Cyperaceae, Typhaceae, and others), arbors and ferns (Fagaceae, Pinaceae, Ulmaceae, Betulaceae, Juglandaceae in arbors; Polypodiaceae and other Monoletespores and Triletespores in ferns), and the natural logarithmic ratios of these values yield reliable records representing distinct climate stages and periodic cycles. During 800-480 ka, the Yangtze River Delta experienced a relatively stable East Asian summer monsoon (EASM) and East Asian winter monsoon (EAWM), but after that time, both the EASM and EAWM intensified. Within these stages, distinct periodic cycles (including 100-, 41-, and 23-kyr cycles) each indicate orbital control. Such climate stages and cycles are well correlated with palaeoclimate records on the Loess Plateau, implicating the same EASM and EAWM association across the East Asian landmass. Linear interpolation of the absolute age is less robust but can be useful for the last 800 ka when there is no alternative dating method.