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An absolute-dated, bi-decadal-resolution, stalagmite oxygen-isotopic time series from Shigao Cave reveals the evolution of summer monsoon precipitation over the past 9.9 ka BP in northern Guizhou Province, Southwest China. The δO-inferred climate conditions are divisible into three distinct stages: (1) a maximum humid era from 9.9-6.6 ka BP; (2) a gradual declining precipitation interval between 6.6-1.6 ka BP; and (3) a relatively low precipitation time window after 1.6 ka BP. Consistency of contemporaneous stalagmite Holocene δO records between Shigao and other caves in the Indian and East Asian monsoon realms support the effect of primary orbital solar forcings on monsoonal precipitation. However, statistical analysis shows a significant spatial asynchroneity of the Holocene Optimum termination in the Asian monsoon territory. The Holocene Optimum ended at 7.2-7.4 ka BP in Oman, located in the Indian monsoon region, and at 5.6-5.8 ka BP in Central China, in the East Asian monsoon zone. In Southwest China, the termination occurred between these periods, at 6.6-7.0 ka BP, and was influenced by both monsoon systems. We propose that this spatially asynchronous ending of Holocene Optimum in Asia may be attributed to sea surface temperature changes in the western tropical Pacific, which is a primary moisture source for the East Asian monsoon. [ABSTRACT FROM AUTHOR]

The causal correlation or linkage between the East Asian Monsoon (EAM) intensity and rise/fall of Chinese dynasties recently proposed by high-resolution paleoclimate reconstructions is examined in detail. Aside from many exceptions to the correlation, both instrumental and historical climate records show strong spatial variations of rainfall on annual-to-decadal scales over eastern China. The relationship between rainfall and EAM intensity also exhibits regional disparity. These observations suggest: (1) Taking paleo-proxy records from a single locality in eastern China to imply changes in drought/wetness as to affect the cultural and political history of China is fraught with uncertainty. (2) On annual-to-decadal scales, the thesis that δ18O in speleothems can be used as a proxy for the EAM strength lacks empirical underpinnings. [ABSTRACT FROM AUTHOR]

The mid-Pleistocene vermiculated red soils (VRS) from Xuancheng (Anhui Province) and Bose (Guangxi) are studied through soil micromorphological, mineralogical and chemical approaches. The results indicate a polygenetic nature of the VRS, having experienced multiple soil-forming stages. Three main stages have been recognized, attributable to distinct climate regimes. They include the formation of the homogeneous matrix of a red soil (stage 1), development of the white veins within the soil profile (stage 2), and formation of juxtaposed textural features (stage 3). The white veins, resulting from iron-depletion in the groundmass of the homogeneous matrix of a red soil, required abundant rainfall without significant seasonal desiccations. The geographically widely spread VRS south of the Yangtze River in China implies a Mid-Pleistocene extreme East Asian summer monsoon. This climate extreme might be closely linked with the changes in the strength of NADW. [ABSTRACT FROM AUTHOR]