| 引用本文: | 龙宜澧，刘星星，王婷，孙有斌.2021.末次间冰期以来渭河盆地沉积相变化及其影响[J].地球环境学报,12(4):389-401, 410 |
| LONG Yili, LIU Xingxing, WANG Ting, SUN Youbin.2021.Paleoenvironment evolutions recorded in the Weihe Basin sedimentary since the last interglacial[J].Journal of Earth Environment,12(4):389-401, 410 |
|
| 摘要: |
| 渭河盆地南依秦岭、北邻黄土高原，保存了巨厚的风尘河湖相沉积序列，是研究新生代气候环境演化的理想场所。以位于西安凹陷区域的西安市鄠邑区正庄村获取的14 m钻孔岩心作为研究对象，通过与邻近的渭南黄土剖面粒度曲线和全球LR04深海氧同位素曲线对比，构建了岩心序列的年代标尺，利用粒度、磁化率等指标探讨风尘-湖相沉积对风力和水动力的不同响应。对粒度测试结果采用威布尔分布（Weibull-distribution）拟合方法，提取了4个粒度组分指示不同沉积相及变化，结果表明：（1）西安凹陷鄠邑地区在末次间冰期结束时发生了一次沉积相变，由湖泊沉积转向风成沉积；（2）尽管沉积相发生变化，粒度指标对沉积环境变化响应仍然敏感，与黄土和石笋记录可良好对比，揭示出末次间冰期以来渭河盆地沉积环境的显著变化。 |
| 关键词: 渭河盆地 风尘湖相沉积 粒度变化 古环境意义 |
| DOI：10.7515/JEE212001 |
| CSTR： |
| 分类号: |
| 基金项目:中国科学院战略性先导科技专项（B类）（XDB40000000）；国家自然科学基金项目（41807425）；黄土与第四纪地质国家重点实验室开放基金（SKLLQG1633） |
|
| Paleoenvironment evolutions recorded in the Weihe Basin sedimentary since the last interglacial |
|
LONG Yili, LIU Xingxing, WANG Ting, SUN Youbin
|
|
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. CAS Center for Excellence in Quaternary Science and Global Change, Xi’an 710061, China
4. Institute of Global Environmental Change, Xi’an Jiaotong University, Xi’an 710054, China
|
| Abstract: |
| Background, aim, and scope The Weihe Basin, enclosed by the Chinese Loess Plateau to the north and the Qinling Mountains to the south, is an outstanding, world-class continental site for obtaining high-resolution multi-proxy records that reflect environmental changes spanning most of the Cenozoic. To reconstruct its paleoenvironment changes since the last interglacial, it’s necessary to clarify the evolution history of sedimentary facies and the climate significance of proxies. By studying the samples from the sedimentary center of the Weihe Basin and comparing of other loess and stalagmite archives, the changes of facies and paleoenvironments were revealed. Materials and methods A 14 m core was drilled in Zhengzhuang Village (ZZC), Xi’an City. Grain-size distributions and magnetic susceptibilities were measured by a Malvern Mastersizer 2000 laser instrument and a Bartington MS2 meter, respectively. The single specimen unmixing based on Weibull distribution was also performed to grain-size distributions to extract the potential paleoclimate signals. A refined chronological framework was established by correlating our grain-size data to an adjacent loess profile that has high-resolution OSL dates and the benthic δ18O timescale LR04. Results A refined chronological framework since the last interglacial was established. By using the grain-size distribution unmixing approach, four major components (i.e. end-members), which are sensitive to aeolian and fluvial sedimentary processes to varying degrees, were distinguished from the grain-size compositions of the core. Discussion The analysis of physical proxies of the ZZC core indicates a sedimentary facies transition occurred around 80 ka. The transition has a great influence on the sensibility of magnetic susceptibility to paleoclimate changes. However, the grain size is still a sensitive proxy to reveal the climate evolution, by comparing with other loess and stalagmite archives. Conclusions Our results indicate that a sedimentary facies transition from lake to eolian deposition occurred at the end of the last interglacial. Though frequent changes in sedimentary facies exist, grain-size variations have similar patterns with loess and speleothem records and are sensitive to the palaeoclimatic changes since the last glacial in the Weihe Basin. Recommendations and perspectives The ZZC core has revealed Weihe Basin’s sedimentary facies change since the last interglacial and is significant for the subsequent studies in Weihe Basin. |
| Key words: Weihe Basin aeolian-lacustrine sedimentary grain size paleoenvironment |
