Climatic changes since the last deglaciation inferred from a lacustrine sedimentary sequence in the eastern Nanling Mountains, south China

Abstract

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.

Holocene environmental change at Lake Shudu, Yunnan Province, southwestern China

“…Elsewhere, a decline in Asian monsoon intensity during the mid to late Holocene is inferred from a shift to more positive d 18 O values from *9 ka BP in the Dongge Cave speleothem record located in southern-central China ) and from ca. 6 kcal yr BP in organic and geochemical proxies obtained from Dahu swamp, eastern Nanling Mountains, southern China (Zhong et al, 2010). However, a shift to arid conditions should have triggered vegetation changes (including reduced pollen concentrations associated with a reduction in vegetation cover), but this is not apparent in the 05SD1 pollen record.…”

“…In other parts of the world, abrupt climate changes have also been observed through the Holocene, including North Africa (deMenocal et al, 2000;Chase et al, 2010) and South America (Moy et al, 2002;Mayr et al, 2007), though the relationship (if any) with those in the North Atlantic remains unclear. In Southeast Asia, a region dominated by monsoonal airflow, the records suggest contrasting trends with some sequences suggesting a strengthening of the Asian summer Monsoon during the mid to late Holocene (Thompson et al, 1997) with others implying a weakening of the system Zhong et al, 2010). Determining the timing, magnitude and trend of past climate is crucial for understanding and managing future change across the region.…”

Sediment geochemistry of Dahu Swamp in the Nanling Mountains, South China: implication for catchment weathering during the last 16,000 years

“…Lower DD values, with samples dominated by higher organic components reflect drier marshy conditions, and higher DD values were resulted from the dominance of terrigenous detritus in sediments (Zhong et al 2009). Based on above interpretation, we infer that lower values of TOC and Md, less positive organic d 13 C as well as higher DD, would reflect relatively wetter conditions, thus suggesting the strengthening of the EA summer monsoon and vice versa (Zhong et al 2010b).…”

East Asian Monsoon Precipitation and Paleoclimate Record Since the Last Interglacial Period in the Bohai Sea Coastal Zone, China

“…These changes have been documented in terrestrial records such as loess-paleosol deposits in northern China (Liu 1985;Porter and An 1995;An 2000), aeolian deposits in north-central China (Li et al 2000;Du et al 2011Du et al , 2012, lacustrine deposits in northern and southern China (Shen et al 2005;Zhong et al 2010), and stalagmites in southern and eastern China (Wang et al 2001;Yuan et al 2004). However, research conducted on records from the coastal environment has been insufficient.…”