【摘要】 中国南方更新世红土是古气候环境变化研究非常重要的载体之一,红土微生物类脂分子是其古气候环境研究的有效指标,但其在红土中的古气候意义需要更进一步的挖掘和明确.选取处于气候变化敏感地带并且已有很好年代学基础的安徽宣城红土剖面进行详细的野外调查和系统的样品采集,利用改善后的碱式水解法提取红土微生物类脂分子,通过对比分析、比较印证等方法对其中的甘油二烷基链甘油四醚(glycerol dialkyl glycerol tetraethers,简称GDGTs)进行系统研究.宣城剖面GDGTs分布特征显示:剖面下部各指标呈旋回性变化、而上部相对稳定,表明形成初期环境比较动荡,而后期成土环境相对稳定;土壤pH为7.0~8.0,推测其物源主要来源于北方干旱区或长江中下游干涸河滩沉积;BIT指标反映宣城地区在130ka BP左右气候极为干旱.结果表明,红土中微生物类脂物GDGTs能够定量、高分辨率地重建安徽宣城的古气候环境,具有重要的研究意义.更多还原

【Abstract】 Abundant information about paleo-environment,paleo-climate and paleolithic culture can be obtained from the red earth in southern China.However,the vermicular paleosol is proposed to be incapable of interpretating the original information about the past climate and envrionment changes owing to the intensive pedogenesis in the tropical-subtropical area.Therefore,previous studies on bio-climatic approaches including pollen,spore fossils and phytoliths are also believed to be not suitable for such kind of stratigraphy.Despite that some studies show the microbial molecular fossils are useful in the paleo-environment reconstruction,but their implications in red earth need to be further explored and confirmed.It is necessary to introduce some new methods to extract the detailed biological information in the red earth.In this study,we collected red earth samples from the Xuancheng section,Anhui Province in the Middle-Lower Reaches of the Yangtze River,which is well-dated and sensitive to climate change.Microbial lipids in the red earth are extracted by employing alkaline hydrolysis combined with the field survey and the laboratory investigation.The characteristics of the microbial lipids,especially glycerol dialkyl glycerol tetraethers(GDGTs)are investigated.The distributions of GDGTs from the Xuancheng profile show that all GDGT-derived proxies in the lower part of profile fluctuates frequently,whereas they are relatively stable in the upper part,which indicates that the paleo-environment changed frequently during the early period of this profile but the later soil environment was relatively stable.The CBT-inferred soil pH ranges from 7.0to 8.0,indicating that the soil parent material likely comes from the arid areas in northwestern China or alternatively from the dry river sediments in the Middle-Lower Reaches of the Yangtze River.The low BIT values suggest that it was very dry at 130 ka BP in the Xuancheng region.更多还原