Phytolith records of the climate change since the past 15000 years in the middle reach of the Yangtze River in China

摘要

Based on 14C dating and core sediments survey, phytolith records are employed to reconstruct paleovegetation and paleoclimate in the Jianghan Plain in the middle reach of the Yangtze River. Phytoliths identified are assigned into 21 well-described morphotypes and divided into four groups (Poaceae, fern, coniferous and broad-leaved). The phytolith assemblages together with warmth index (I w) are divided into 18 ecological zones, which reflect a complete vegetation history related to climate change in the middle reach of the Yangtze River during the past 15000 years. On the basis of the correlation of phytolith records with the paleoclimatic indicators from stalagmite, peatland, North Atlantic deep-sea sediments, Loess Plateau of Central China, and Arabic Sea sediments, eight climatic phases are identified included Last Glacial Maximum (LGM) (20–14.8 cal kaBP), Last Deglaciation (LDG) (14.8–11.9 cal kaBP), low-temperature phase in the Early Holocene (11.9–8 cal kaBP), Holocene Optimum (8–4.9 cal kaBP), Holocene Katathermal (4.9–1.1 cal kaBP), Medieval Warmth Period (MWP) (1.1–0.7 cal kaBP), Little Ice Age (LIA) (0.7–0.15 cal kaBP), and Modern Warming (0.15 cal kaBP — present). Climatic events such as Bolling-Allerod warm intervals, Older Dryas, Inter-Allerod Cold Period, and Younger Dryas, and eight Holocene Bond events (B1–8) have been identified since the LDG. Our results demonstrate that the evolution of the climate in the research area has a strong link with the Indian Summer Monsoon (SW Monsoon), Asian Summer Monsoon (SE Monsoon), and Holocene events in North Atlantic simultaneously, which might indicate that solar variability affects the Earth surface climate system at the centennial and millennial scales.