Reconstruction of late glacial and Holocene climate evolution in southern China from geolipids and pollen in the Dingnan peat sequence

摘要

We have carried out a multi-proxy analysis of a radiocarbon-dated peat core that records the history of paleoclimate change dating from 18 ka in the Dingnan region of southern China. Fatty acid and hydrocarbon distributions, total organic carbon (TOC) concentrations, pollen assemblages and sediment lithology reveal a succession of three major paleoclimate intervals. Plant waxes are the predominant origin of the n-alkanoic acid and n-alkane compositions of this sedimentary sequence. Contributions of these geolipid components vary relative to TOC and with changes in lithology and help to refine a pollen-based reconstruction of local paleoclimate evolution. A period of cool and fairly wet climate (15,630-10,450 cal aBP) follows accumulation of coarse fluvial sediments under relatively dry deglacial conditions. The second period (10,450-6040 cal aBP) experienced the warmest climate and the highest precipitation, indicated by a minimum C-18:1/C-18:0 ratio, together with the low CPI values of n-alkanes and high ACL values. The third time interval (6040-3800 cal aBP) was a moderately dry and cool period. The climate record of the most recent period (< 3800 cal aBP) is obscured by agricultural disturbance. The Younger Dryas (12,900-11,600 cal aBP) appears in this record as a period of variable and very wet climate. During the interval 10,450-6040 cal aBP, both temperature and the precipitation/evaporation ratio maximized. Therefore, we consider this period to represent the Holocene Optimum which coincides with that of the northern hemisphere. Moreover, our results do not fit the spatially asynchronous pattern of the East Asian monsoon Holocene Optimum in China suggested by previous studies. They instead parallel the pattern of global paleoclimate change and consequently show that the evolution of Holocene paleoclimate in southern China is consistent with changes in northern hemisphere solar radiation. (c) 2005 Elsevier Ltd. All rights reserved.