| 引用本文: | 黄守毅，蔡演军，吕雁斌，贺梅，成星，程海，
R. Lawrence Edwards.2021.贵州七星洞石笋文石-方解石序列记录的气候变化[J].地球环境学报,12(6):632-640 |
| HUANG Shouyi, CAI Yanjun, LÜ Yanbin, HE Mei, CHENG Xing, CHENG Hai, R. Lawrence Edwards.2021.Climate change recorded by an aragonite-calcite stalagmite in Qixing Cave, Guizhou[J].Journal of Earth Environment,12(6):632-640 |
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| 摘要: |
| 文石-方解石型石笋的矿物相变化可能与气候环境变化存在联系，但中国季风区有关此类石笋的古气候研究比较匮乏。本文对七星洞一个文石-方解石型石笋开展了岩石学鉴定和氧、碳同位素组成分析，发现其文石层的出现与δ18O值、δ13C值的显著偏正存在联系，通过对文石形成的可能机制和δ18O、δ13C值变化的一般规律进行综合分析，验证了该类石笋中文石层出现指示气候干旱的论点。将石笋校正后的方解石δ18O序列与董哥洞δ18O记录进行对比，发现七星洞石笋QXZ文石层指示的干旱事件与董哥洞记录中的弱季风事件存在一定的对应关系，因此，研究该类型石笋的矿物相变化对于全面认识研究区季风变化历史具有重要意义。 |
| 关键词: 石笋 方解石 文石 δ18O 气候变化 |
| DOI：10.7515/JEE212023 |
| CSTR：32259.14.JEE212023 |
| 分类号: |
| 基金项目:国家重点研发计划项目（2017YFA0603401）；中国科学院战略性先导科技专项（B类）（XDB40010200） |
| 英文基金项目:National Key Research and Development Program of China (2017YFA0603401); Strategic Priority Research Program of the Chinese Academy of Sciences (XDB 40010200) |
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| Climate change recorded by an aragonite-calcite stalagmite in Qixing Cave, Guizhou |
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HUANG Shouyi, CAI Yanjun, LÜ Yanbin, HE Mei, CHENG Xing, CHENG Hai, R. Lawrence Edwards
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1. State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences, Xi’an 710061, China
2. University of Chinese Academy of Sciences, Beijing 100049, China
3. Institute of Global Environmental Change, Xi’an Jiaotong University, Xi’an 710049, China
4. CAS Center for Excellence in Quaternary Science and Global Change, Xi’an 710061, China
5. Department of Earth Sciences, University of Minnesota, Minneapolis 55455, USA
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| Abstract: |
| Background, aim, and scope The alternate deposition of aragonite and calcite in stalagmite is generally related to climate and environment changes. However, using stalagmite with interbedded layers of aragonite and calcite for paleoclimate reconstruction in regions affected by Asian monsoon in China is still scarce. In this study, we investigate the occurrence of interbedding aragonite and calcite in a stalagmite from Qixing Cave, southern China and its relations to the regional climate changes by combining petrographic and stable isotope (δ18O and δ13C) analysis. Materials and methods QXZ is a calcite stalagmite with several aragonite layers collected in Qixing Cave, Guizhou Province, southern China. Four thin sections with a standard thickness of 30 μm were prepared for petrographic analysis and observed by Olympus BX60 polarizing microscope at the Institute of Earth Environment, Chinese Academy of Sciences (IEECAS). Seventeen subsamples for dating were drilled along the growth layers of the stalagmite at different depths and then dated at the Isotope Laboratory, Department of Earth Sciences, University of Minnesota using inductively coupled plasma mass spectrometric techniques (SC-ICP-MS). A total of 451 sub-samples were collected by scraping along the growth axis at an interval of ~0.05 mm and analyzed by Finnigan MAT-252 at IEECAS. Results According to the petrographic observations, it is found that white layers in QXZ are composed of aragonite, while the remaining layers consist of calcite. Dating results show that the stalagmite QXZ deposited during the last ~10 ka, and the age-depth chronology is established by linear interpolation. What can be intuitively noted is that the abrupt positive shift of δ18O and δ13C are associated with the appearance of aragonite. Discussion The precipitation of needle-like aragonite in QXZ indicates that the aragonite layers may deposit under arid conditions. The appearance of aragonite layers keeps pace with the positive shifts of δ18O and δ13C, indicating that a common factor dominates both of them. After calibrating the isotope composition of the aragonite to that of calcite in stalagmite QXZ, the δ18O values of aragonite layers are still relatively higher than those of calcite layers, further verifying that the appearance of QXZ aragonite layers is associated with arid conditions. By comparing the calcite δ18O series of QXZ with the δ18O records from Dongge Cave, it is apparent that the drought events indicated by aragonite layers, and also enriched δ18O and δ13C, in QXZ largely correspond to the weak monsoon events in Dongge records. Conclusions The occurrence of aragonite layers in aragonite-calcite stalagmites may indicate decreased precipitation (or drought events). And the well correspondence between aragonite layers and the weakening of monsoon highlights the great importance of alternate deposition of aragonite and calcite in stalagmites for understanding the climate changes. Recommendations and perspectives In the Asian Monsoon regions, there is still a lack of paleoclimate research on aragonite-calcite stalagmites. Whether the appearance of aragonite layers corresponding to the drought events/weak monsoon events is applicable to stalagmites from varied locations still requires further research. |
| Key words: stalagmite calcite aragonite δ18O climate change |
