为进一步理解末次冰消期以来东亚夏季风(EASM)变化的时空特征,特别是中原地区全新世EASM的时空格局及其驱动机制,在AMS 14C年代的支持下,本文基于荥阳盆地湖相—湿地相剖面的正构烷烃和沉积学指标(粒度和总有机碳),重建了荥阳盆地～17.8 cal ka BP以来的气候与环境变化历史.重建结果表明,～17.8-～11.7 cal ka BP是草原环境下的黄土状堆积阶段.～11.7-～8.5calkaBP为湿地沉积时段,是森林和湿地扩展的时期.～8.5-～2.8 cal ka BP为湖泊存在时段,木本植物和水生植物丰度达到最高后波动降低.～2.8-～2.4 cal ka BP为湿地存在阶段,菌藻类和/或微生物、沉水浮游植物的烷烃贡献量很大.～2.4-～1.1 calkaBP为草原环境下的黄土沉积时段.本文进一步基于荥阳盆地长链正构烷烃的平均碳链长(ACL27-33,简称ACL)和C27+29/C31+33比值,结合渑池盆地木本花粉百分含量和禾本科/(蒿属+藜科)比值,重建了中原地区全新世以来湿度变化,并与长江中下游地区和中国北方地区(指黄河以北地区)的全新世湿度序列进行了对比.对比结果显示,全新世中期的干旱时段(～7.0-～4.0 cal ka BP或～8.0-～5.0 cal ka BP)与长江中下游地区全新世中期的干旱时段基本对应.这一时段的干旱对应于厄尔尼诺—南方涛动(ENSO)强度的较低值(即La Nino态)时段和赤道西太平洋SST较高温时段.控制上述EASM影响区的中国中部地区全新世湿度空间格局的主要机制可能是ENSO状态以及由ENSO调控的亚热带西太平洋高压(WPSH)的南北向移动.
Climate and environmental changes since the last deglaciation in the Xingyang Basin of the Central China Plains
In order to depict the spatiotemporal patterns of EASM variations(EASM:East Asian Summer Monsoon)since the last deglaciation,we analyzed n-alkane compositions and sedimentological characteristics of a lacustrine-wetland section(namely ZWZ-1 section)in the Xingyang Basin of the Central China Plains.We also reconstructed the climatic and environmental changes since～17.8 cal ka BP on the basis of the analytical results.The reconstruction displayed five-staged variations:(1)～17.8-～11.7 cal ka BP was a period of loess-like sediment accumulation under.a steppe-dominating environment;(2)～11.7-～8.5 cal ka BP was a period of wetland deposition,during which the n-alkane-indicated forest and wetland expanded;(3)～8.5-～2.8 cal ka BP was a period of lacustrine deposition and also a period of maximal woody and aquatic plant n-alkane components;(4)～2.8-～2.4 cal ka BP was again a period of wetland deposition when the n-alkane components of bacteria,algae/microorganisms and submerged phytoplankton increased dramatically;(5)～2.4-～1.1 cal ka BP was a loess deposition period under a steppe-dominating environment.We also compared the Holocene moisture sequences(ZWZ-1 section and MC-1 section)from the Central China Plains with those from the middle and lower reaches of the Yangtze River and also with those from northern China.The moisture sequence at ZWZ-1 section was based on the average chain length of long-chain n-alkanes(ACL27-33)and C27+29/C31+33 ratio and the moisture sequence at MC-1 section was based on tree pollen(％)and Poaceae/(Artemisia+Chenopodiaceae)ratio.Our comparison shows that the mid-Holocene drought(～7.0-～4.0 cal ka BP or～8.0-～5.0 cal ka BP)in the Central China Plains chronologically corresponded with the mid-Holocene drought in the middle and lower reaches of the Yangtze River.It seems that the mid-Holocene drought in the entire central China(including the middle and lower reaches of the Yangtze River and the Central China Plains)was causally associated with lowered El Nino-Southern Oscillation(ENSO)intensity and also with elevated Sea Surface Temperature(SST)in the western Tropical Pacific.This implies that the spatiotemporal patterns of the Holocene moisture variations in the entire central China were controlled by ENSO state and modulated by ENSO-dictated north-south shift of West Pacific Subtropical High(WPSH).
Xingyang Basinn-alkaneHoloceneEast Asian Summer MonsoonEl Niño-Southern Oscillation
万方数据
维普
