Two sediment cores recovered from Dahu Swamp, which is located in eastern Nanling Mountains in south China, were selected for investigation of palaeoclimatic changes. Multi-proxy records of the two cores including lithological variation, organic carbon isotope ratio, dry bulk density, organic matter content, magnetic susceptibility, humification degree, median grain size and geochemical proxies reveal that during the last deglaciation three drier phases correspond to the Oldest, Older and Younger Dryas cooling events, and the intercalated two wetter phases synchronise with the Bølling and Allerød warming events. The Holocene Optimum, which was resulted from a strengthening of the East Asian (EA) summer monsoon, occurred in the early and mid Holocene (ca. 10-6 cal. ka BP). In the mid and late Holocene (ca. 6-3 cal. ka BP), a prevailing dry climate suggested a weakening of the EA summer monsoon. The general trend of Holocene climatic changes in this study agrees with the 258 N summer solar insolation, suggesting that orbitally induced insolation may have played an important role in the Holocene climate in the study region.

Zhong, W., Ma, Q. H., Xue, J. B., Zheng, Y. M., Cai, Y. & Ou, Y. J. 2009: Humification degrees of a lacustrine sedimentary sequence as an indicator of past climatic changes in the last c. 49 000 years in South China. Boreas, 10.1111/j.1502‐3885.2009.00119.x. ISSN 0300‐9483. An 860 cm long sediment core recovered from Dahu Swamp was used to test the potential of the degree of humification (expressed as the corrected absorbance values, HDcab) of lacustrine sediments as an indicator of past climatic changes in South China. The chronological sequence of this core was established using 10 AMS 14C dates and 10 conventional 14C dates and gives the bottom age of c. 48 800 cal. yr BP. Based on comparisons with multiproxy records, such as lithological variation, organic carbon isotope ratio, organic matter content and dry bulk density, we infer that the HDcab record is sensitive to local hydrological variations that are closely related to the East Asian (EA) summer monsoon precipitation. Higher HDcab values would indicate relatively drier conditions, suggesting a weakening of the EA summer monsoon and vice versa. Based on the HDcab, as well as other multiproxies, the climatic history in the last c. 49 000 years in the swamp area shows agreement with the Chinese stalagmite record and with the 25°N summer solar insolation, implying that orbitally induced insolation may have played a role in the last glacial period (LGP) climate in South China. Several millennial‐scale dry phases during the LGP show similarities with the stadials revealed by the ice core record in Greenland and from the Chinese cave stalagmites. Our study demonstrates that the HDcab of lacustrine sediments is a useful proxy of past climatic changes in South China.

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This study emphasizes to testify the potential of geochemical proxies of lacustrine sediments as indicative of past climatic changes since the last deglaciation over the catchment of a small closed lake in South China. Based on the study on the core K02 from Dahu Swamp, a small lake in the eastern Nanling Mountains, we inferred that chemical features of clastic materials, which were mainly derived from the granite weathering crust and transported by surface runoff into this lake, possibly had played an important role in affecting chemical characteristics of the sediments. Wetter climatic conditions would lead to stronger chemical weathering intensity (CWI), resulting in more soluble and mobile elements being easily leached downward in granite weathering crusts and the insoluble ones being enriched in the top materials of the weathering crusts. In contrast, dry conditions would exert a converse influence. Although this study presents a different climatic implication of geochemistry from lacustrine sediments in South China from that in north-central China, the results demonstrate that chemical elements of sediments in the small lake in South China can be utilized to reflect the CWI, which was closely in association with variations in temperature and precipitation in the lake catchment.

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