白雨洁^1,2,3,,
吴江滢^1,2,3,,,
梁怡佳^1,2,3,
邵庆丰^1,2,3
1. 南京师范大学地理科学学院, 江苏 南京 210023
2. 虚拟地理环境教育部重点实验室(南京师范大学), 江苏 南京 210023
3. 江苏省地理信息资源开发与利用协同创新中心, 江苏 南京 210023

基金项目: 国家自然科学基金项目（批准号：41372174）和江苏省研究生科研与实践创新计划项目（批准号：KYCX19-0789）共同资助


详细信息

作者简介: 白雨洁, 女, 23岁, 硕士研究生, 自然地理学专业, E-mail:baiyujie0317@163.com

通讯作者: 吴江滢, E-mail:09196@njnu.edu.cn

中图分类号: P597⁺.2;P532

收稿日期:2020-01-20
修回日期:2020-05-12
刊出日期:2020-07-30

THE MULTI-PROXY RECORD OF A STALAGMITE FROM YULONG CAVE,HUBEI DURING THE 4.2 KA EVENT

Bai Yujie^1,2,3,,
Wu Jiangying^1,2,3,,,
Liang Yijia^1,2,3,
Shao Qingfeng^1,2,3
1. School of Geography, Nanjing Normal University, Nanjing 210023, Jiangsu
2. Key Laboratory of Virtual Geographic Environment(Nanjing Normal University), Ministry of Education, Nanjing 210023, Jiangsu
3. Jiangsu Center for Collaborative Innovation in Geographical Information Resource Development and Application, Nanjing 210023, Jiangsu


More Information

Corresponding author: Wu Jiangying,E-mail:09196@njnu.edu.cn

MSC: P597⁺.2;P532

--> Received Date: 20 January 2020
Revised Date: 12 May 2020
Publish Date: 30 July 2020


摘要
摘要:利用湖北神农架利川市玉龙洞一支长约400 mm的石笋（TCL），结合稳定同位素、微量元素以及灰度等多指标重建了14.4 ka B.P.~2012 A.D.时段十年际分辨率的东亚地区气候与环境变化。该时段内，δ¹⁸O变化范围为-9.5 ‰~-6.6 ‰，平均值为-8.48 ‰。该记录与亚洲季风区同时段其他石笋记录重现性良好，说明石笋δ¹⁸O可以较好地反映轨道至千年尺度的亚洲夏季风强度变化。结合其δ¹³C、微量元素以及灰度重建了多指标气候变化。石笋δ¹³C变化范围是-8.2 ‰~-3.8 ‰，围绕均值-5.4 ‰上下波动，主要存在千年尺度振荡，反映了洞穴上覆植被覆盖率和土壤CO₂产率的变化。石笋TCL的灰度值、Sr/Ca和Ba/Ca比值与δ¹³C值在千年尺度波动上对应关系良好，间接指示了与当地水热条件相关的洞穴水文状况变化。石笋灰度与δ¹³C值对应关系良好，间接指示了干湿度或降雨量的变化。石笋中Sr/Ca和Ba/Ca变化的总体趋势基本一致，主要受当地降水量控制下土壤淋滤作用变化的影响。TCL δ¹⁸O序列显示"4.2 ka事件"的起止时间段为4.4~4.1 ka B.P.，整体呈现"缓慢开始，快速结束"的结构特征。此时段其δ¹³C值偏正，灰度以及微量元素代用指标趋势均呈现低值，这种不同指标间出现的协同变化，说明当时利川地区降水量减少，局域环境明显偏向干冷。文章推测此次干旱事件的发生是由于大量淡水注入北大西洋，海表温降低，使得赤道辐合带（ITCZ）南移，进而引起北半球中低纬度季风减弱并得以在石笋多指标记录中反映。
关键词: 全新世/
4.2 ka事件/
玉龙洞/
石笋/
多指标

Abstract:The Yulong Cave (30°39'N, 109°13'E) is located in Mt. Shennongjia, Hubei Province, Central China. The site is strongly influenced by the East Asian Monsoon, with a mean annual rainfall of about 1460 mm and an average annual temperature of about 12.6℃. A 400 mm-long and candle-shaped stalagmite (sample No. TCL) was derived from Yulong Cave. The polished profile of sample TCL shows that it is mainly composed of white calcite, without obvious hiatuses throughout. We conducted 15²³⁰Th dating, stable isotope, trace element and grey level analysis on the stalagmite TCL, thus reconstructed paleoclimate and environment changes covering an interval from 14.4 ka B.P.~2012 A.D. The dating measurements were finished by multi-collector inductively coupled plasma spectrometer (MC-ICP-MS) at two labs, the Institute of Global Environmental Change, Xi'an Jiaotong University, China, and School of Geography, Nanjing Normal University, China. The ²³⁰Th results are in stratigraphic order with a standard error of ±2σ. The δ¹⁸O and δ¹³C were analyzed on a Finnigan MAT-253 mass spectrometer fitted with a Kiel Carbonate Device at School of Geography, Nanjing Normal University, China. The trace element data (Sr/Ca and Ba/Ca) were collected using a X-ray Fluorescence (XRF) at the Key Laboratory of Surficial Geochemistry, Nanjing University, China. The grey level was obtained from a high-resolution image using ENVI 4.0 software traversing down the growth axis and it represents the albedo of the polished surface.
The δ¹⁸O values vary from -9.5 ‰ to -6.6 ‰, following the orbital solar insolation changes on the long-term trend. The good replication of our δ¹⁸O record with stalagmite records from Dongge Cave, Sanbao Cave and Hulu Cave in the Asian monsoon domain indicates that stalagmite δ¹⁸O can reflect the Asian monsoon climate changes on the orbital to millennial timescales. The δ¹³C values range from -8.2 ‰ to -3.8 ‰, with large millennial variations fluctuating around the mean value of -5.4 ‰. On the millennial timescale during the Holocene, the δ¹⁸O and δ¹³C displays a good correlation, with depleted δ¹³C corresponding to decreased δ¹⁸O. This suggests that δ¹³C of TCL mainly reflects the changes of vegetation biomass and terrestrial CO₂ productivity under the influence of monsoon. The grey level ranges from 70 to 200, with higher values corresponding to white and yellowish opaque section of the stalagmite TCL. There is also a good correlation between the grey level and the δ¹³C values. Furthermore, the similar millennial trend of Sr/Ca and Ba/Ca changes is also found. The multi-proxy records of the sample TCL, including the δ¹³C data, trace-element ratios and grey levels have similar changing characteristics on the millennial timescale, with low δ¹³C values corresponding to high grey levels and trace element enrichments, and vice versa. This suggests that they are controlled by a same process, possibly the change of cave hydrology dominated by the local precipitation and vegetation biomass.
The δ¹⁸O record of TCL reflects that the "4.2 ka event" occurred from 4.4~4.1 ka B.P., and it is characterized with a slow start and a fast end. During this episode, the δ¹³C values remain positive, and grey scale and trace element values are low. The corresponding changes between the different indicators together demonstrate a dramatic decrease in local precipitation amount and biomass, namely a drought event, because of the weak monsoon. Besides, the slow dripwater rate which leads to the minimum value of growth rate in stalagmite (17.4 μm/a) further supports the occurrence of the drought. There is a significant similarity between the TCL δ¹⁸O value with the Greek and Arabian Sea records, indicating that the southward shift of the intertropical convergence zone (ITCZ) leads to weakening of the monsoon in the northern hemisphere and occurrence of the drought "4.2 ka event".
Key words:Holocene/
4.2 ka Event/
multi-proxy evidence/
Yulong Cave/
stalagmite



PDF全文下载地址:

http://www.dsjyj.com.cn/data/article/export-pdf?id=dsjyj_11797