石笋灰度和同位素对末次冰期气候事件的响应  

The response of stalagmite gray-level and isotopes to the climatic events during the last glacial period

作　　者：王萌 陈仕涛[1,2,3] 黄琬淳 蔡雯沁 龚清霖 梁怡佳 王先锋 汪永进 WANG Meng;CHEN Shi-tao;HUANG Wan-chun;CAI Wen-qin;GONG Qing-lin;LIANG Yi-jia;WANG Xian-feng;WANG Yong-jin(Key Laboratory of Virtual Geographic Environment,Ministry of Education,School of Geography Science,Nanjing Normal University,Nanjing 210023,China;State Key Laboratory of Cultivation Base of Geographical Environment Evolution(Jiangsu Province),Nanjing 210023,China;Jiangsu Center for Collaborative Innovation in Geographical Environment Resource Development and Application,Nanjing 210023,China;Department of Marine Science and Engineering,Nanjing Normal University,Nanjing 210023,China;Nanyang Technological University,Earth Observatory of Singapore,Singapore 639798,Singapore)

机构地区：[1]南京师范大学地理科学学院,虚拟地理环境教育部重点实验室,南京210023 [2]江苏省地理环境演化国家重点实验室培育建设点,南京210023 [3]江苏省地理信息资源开发与利用协同创新中心,南京210023 [4]南京师范大学海洋科学与工程学院,南京210023 [5]南洋理工大学,新加坡地球观测研究所,新加坡639798

出　　处：《自然资源学报》2020年第12期3064-3075,共12页Journal of Natural Resources

基　　金：国家自然科学基金项目(41931178,41572340);江苏高校优势学科建设工程(164320H116)。

摘　　要：对石笋多指标的研究有利于全面理解季风气候事件的变化特征和机制。以湖北永兴洞YX55石笋为研究对象,通过高精度U/Th定年和多指标分析重建了65~35 ka B.P.石笋灰度和稳定同位素的变化序列。在65~40 ka B.P.时段,石笋灰度、δ13C与δ18O都呈现出数个千年至亚千年尺度的变化,但δ13C变化幅度比δ18O小得多。这说明灰度和δ13C这类代表局域气候的指标,都响应于δ18O指示的Heinrich(H)事件和Dansgaard-Oeschger(DO)旋回,但响应的程度各不相同。H4期间,石笋δ13C和灰度呈现不一致变化:δ13C不像在其他H事件一样小幅振荡,而是大幅正偏(相当于其他H事件2~3倍);灰度则显示出和DO旋回一致的特征。这种δ13C/灰度与δ18O异常响应关系可能的机制是:H4期间季风强度急剧减弱,使得洞穴上覆土壤覆盖率大幅降低,从而削弱或阻止了土壤-岩溶系统的过滤能力,使石笋中杂质含量异常增加。The study of various proxies of stalagmites is conducive to understand the characteristics and mechanisms of monsoon climate events comprehensively. Here, we present a high-resolution and multi-proxy stalagmite record from Yongxing Cave, Central China,spanning the interval between 65 and 35 ka B.P. based on high precision U/Th dating method and multi-proxy analyses. A total of 371 subsamples were drilled for oxygen and carbon isotopic measurements along the growth axis at a spacing of 0.5-mm-diameter carbide dental burrs. The analyses were conducted using a Finnigan MAT 253 mass spectrometer linked to a Kiel Carbonate Device at the School of Geography, Nanjing Normal University. The precision is 0.06‰ for δ18 O and 0.05‰ for δ13 C at the 1σ level. For the gray-level measurements, the polished surface of the studied section was scanned at a resolution of 1200 dpi using an EPSON Perfection 4990 Photo Scanner. The gray level was then obtained from the image using the Environment for Visualizing Images(ENVI 4.8) software while traversing down the growth axis. The values range between 0 and 442, with a spatial resolution of 20 μm. The experimental results show that during the period of 65-40 ka B.P., the stalagmite records of gray-level, δ13 C and δ18 O all presented millennial to sub-millennial changes, but the amplitude of δ13 C is much smaller than that of δ18 O. This indicates that the local climate indicators of δ13 C, gray-level and lithology also respond to the Heinrich(H) events and Dansgaard-Oeschger(DO) events, but their sensitivities to events are different. During the H4 episode(about 40-38 ka B.P.), δ13 C and the gray-level of the stalagmite showed anomalous changes. The significantly positive shift of δ13 C reached an amplitude of 4.5‰ during H4, which was 2-3 times than other H events, while the gray-level presented the same characteristics to that of the DO cycles. We imply that the state of soil erosion may play an important role in such correspondence during H4. When the monsoon weak

关 键 词：突变事件 灰度 同位素 亚洲季风 

分 类 号：P532[天文地球—古生物学与地层学]