| 引用本文: | 李昀卿,姚昕,秦问,刘祎,庞宇欣,张欣烨,田芳.2025.湖泊沉积物粒度揭示的河北坝上高原全新世环境演变[J].地球环境学报,16(6):671-685 |
| LI Yunqing,YAO Xin,QIN Wen,LIU Yi,PANG Yuxin,ZHANG Xinye,TIAN Fang.2025.Holocene environmental changes revealed by lacustrine sediment grain-size on the Bashang Plateau, Hebei Province[J].Journal of Earth Environment,16(6):671-685 |
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| 湖泊沉积物粒度揭示的河北坝上高原全新世环境演变 |
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李昀卿1，姚昕1，秦问1，刘祎2，庞宇欣3，张欣烨1, 4，田芳1*
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1. 首都师范大学 资源环境与旅游学院，北京 100048
2. 北京市昌平区第二中学，北京 102299
3. 北京师范大学 地理科学学部，北京 100875
4. 首都师范大学 初等教育学院，北京 100048
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| 摘要: |
| 河北坝上高原位于东亚夏季风边缘区，对季风及气候变化响应敏感，研究其全新世环境演变过程及机制
对认识东亚夏季风演变具有重要意义。以河北坝上高原马连洼湖泊沉积物为研究对象，通过AMS 14C测年结果构建年代框架，开展湖泊沉积物粒度、总有机碳（total organic carbon，TOC）、总氮（total nitrogen，TN）和C/N（TOC和TN比值）环境代用指标分析，揭示该地区全新世（11530 cal. a BP以来）的气候环境演变过程。坝上地区全新世气候环境演变经历了4个阶段：阶段Ⅰ（11530—8770 cal. a BP），气候波动频繁，其中，全新世早期（11530—10060 cal. a BP）风沙活动较强，植被覆盖度较低，随后（10060—8770 cal. a BP）气候有转暖湿趋势；阶段Ⅱ（8770—5710 cal. a BP）气候最为暖湿，植被覆盖度较高；阶段Ⅲ（5710—3270 cal. a BP）气候转凉转干，陆源有机质来源减少；阶段Ⅳ（3270 cal. a BP以来）入湖径流减少，气候温凉偏干，土地覆被变差。该地区分别在11530—11115 cal. a BP、10400—10000 cal. a BP、7600—7450 cal. a BP、4800—4400 cal. a BP和700—300 cal. a BP这5个时期发生了显著的气候事件，主要表现出较强的冷干气候特征，其中，4800—4400 cal. a BP冷干事件对应4.5 ka事件，700—300 cal. a BP对应小冰期早期。 |
| 关键词: 中国北方 东亚夏季风 马连洼 粒度 端元建模分析 |
| DOI：10.7515/JEE232031 |
| CSTR：32259.14.JEE232031 |
| 分类号: |
| 基金项目:国家自然科学基金项目（42071107） |
| 英文基金项目:National Natural Science Foundation of China (42071107) |
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| Holocene environmental changes revealed by lacustrine sediment grain-size on the Bashang Plateau, Hebei Province |
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LI Yunqing1, YAO Xin1, QIN Wen1, LIU Yi2, PANG Yuxin3, ZHANG Xinye1, 4, TIAN Fang1*
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1. College of Resource Environment and Tourism, Capital Normal University, Beijing 100048, China
2. Changping No.2 High School of Beijing, Beijing 102299, China
3. Faculty of Geographical Science, Beijing Normal University, Beijing 100875, China
4. College of Elementary Education, Capital Normal University, Beijing 100048, China
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| Abstract: |
| Background, aim, and scope The Bashang Plateau (Hebei Province) is located in the fringe area of the East Asian summer monsoon. By studying its climate evolution during the Holocene, a deeper understanding of climate variability events and their mechanisms can be achieved. Such research is necessary for the accurate prediction and assessment of the impacts of extreme climate events on both the natural environment and human society. A sediment core obtained from an inland closed lake provides a good archive of past environmental changes, particularly if it is from a small lake with a small catchment, that is sensitive to environmental changes, as it can be used to reconstruct the local climate from the changes in the environmental proxies. Materials and methods A lacustrine sediment core was collected from Lake Malianwa on the Bashang Plateau. After establishing a reliable age-depth model based on AMS 14C dates and integrating environmental proxies such as grain-size, total organic carbon (TOC), total nitrogen (TN), and the C/N (TOC/TN) ratio, the climate and environmental changes during the Holocene on the Bashang Plateau were reconstructed. Such detailed knowledge of environmental changes and the local climate during the Holocene can then help our understanding of the human-environment relationship in this region. Results The sediment particle size is mainly fine silt. Grain-size data can be separated into 3 end-members: EM1 (mode grain-size: 137.7 μm), has two distinct peaks, representing sand sediment; EM2 (mode grain-size: 19.9 μm) belongs to silty sand; and EM3 (mode grain-size: 5.8 μm) is very fine silt. The C/N ratio ranges between 10 and 20, and the TOC and TN results show a fluctuating trend of first rising and then declining during the Holocene. Based on the change patterns of end-members and the content of TOC, TN, and C/N, the history of environmental changes during the Holocene can be divided into four stages. In stage Ⅰ (11530—8770 cal. a BP), EM1 is at its highest of the four stages, with high values of sand content and EM1 occurring frequently; TOC and TN content are unstable, especially during 11530—10060 cal. a BP where they fluctuate greatly; and from 10060—8770 cal. a BP, the content of sand decreases while TOC content increases. In stage Ⅱ (8770—5710 cal. a BP), all indicators are relatively stable, with a high value for EM2 and a low content of sand and a high content of TOC. In stage Ⅲ (5710—3270 cal. a BP), sand content increases while TOC content and C/N ratio are low. In stage Ⅳ (after 3270 cal. a BP), the proportion of EM3 is high, EM1 reappears frequently, and the average values of TOC and TN become unstable. Discussion Based on the distribution characteristics of the 3 end-members, we attempt to explain the variations of the sedimentary environment: EM1 reflects aeolian sediment, EM2 reflects surface runoff transport material, and EM3 represents lake hydrostatic sedimentation. Between 11530 cal. a BP and 8770 cal. a BP, the climate fluctuated from cold and dry to warm and humid. Sandstorm activities were frequent under the cold and dry climate and vegetation was sparse from 11530—10060 cal. a BP, while a warm and humid climate is inferred alongside increased vegetation productivity from 10060—8770 cal. a BP. The climate is typically warmest and most humid with the highest vegetation cover between 8770 cal. a BP and 5710 cal. a BP. During the period 5710—3270 cal. a BP, the climate turned cool and dry, and the amount of terrestrial organic matter decreased. After 3270 cal. a BP, sandstorm activities again occurred frequently with decreased runoff into the lake, suggesting that the vegetation cover deteriorated with the cooler and drier climate. Significant climate-change events occurred in the region during the following five periods: 11530—11115 cal. a BP, 10400—10000 cal. a BP, 7600—7450 cal. a BP, 4800—4400 cal. a BP, and 700—300 cal. a BP. In general, our interpretation is consistent with existing research on past climate in northern China. Conclusions Sediment grain size, TOC, TN, and C/N records of Lake Malianwa and a regional comparison with Lake Gonghai and Anguli Nur suggest that the overall climate of the region during the Holocene has changed from cold and dry to warm and humid, before reverting to cool and dry. The source of organic matter in the lake was exogenous. The climate change in this region is closely related to variation in the East Asian summer monsoon intensity. Moreover, at the orbital scale, the climate is also influenced by the combined drivers of solar radiation intensity and North Atlantic ice-rafting events. Recommendations and perspectives Environmental characteristics inferred from Lake Malianwa sediments are consistent with existing studies about northern China, supplementing the Holocene climate history record of northern China. |
| Key words: northern China East Asian summer monsoon Malianwa grain-size end-member modeling analysis |
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