贾飞飞^1,,
鲁瑞洁^2,3,4,
高尚玉^2,3,4
1. 辽宁师范大学, 城市与环境学院, 辽宁 大连 116029
2. 地表过程与资源生态国家重点实验室, 北京师范大学地理科学学部, 北京 100875
3. 防沙治沙教育部工程研究中心, 北京师范大学地理科学学部, 北京 100875
4. 环境演变与自然灾害教育部重点 实验室, 北京师范大学地理科学学部, 北京 100875

基金项目: 国家自然科学基金项目（批准号：41601190和41330748）资助


详细信息

作者简介: 贾飞飞, 女, 29岁, 讲师, 自然地理学专业, E-mail:jiafeifei15@163.com

中图分类号: P941.73;P534.63⁺2;P532

收稿日期:2018-03-19
修回日期:2018-06-02
刊出日期:2018-09-30

Environmental changes recorded from grain-size characteristics of the lacustrine-peat sediments from southeastern margin of Mu Us Desert since 12.2 ical.ka B.P.

Jia Feifei^1,,
Lu Ruijie^2,3,4,
Gao Shangyu^2,3,4
1. School of Urban and Environmental Sciences, Liaoning Normal University, Dalian 116029, Liaoning
2. State Key Laboratory of Earth Surface Processes and Resource Ecology, Faculty of Geographical Science, Beijing Normal University, Beijing 100875
3. Engineering Center of Desertification and Blown-Sand Control of Ministry of Education, Faculty of Geographical Science, Beijing Normal University, Beijing 100875
4. Key Laboratory of Environmental Change and Natural Disaster of Ministry of Education, Faculty of Geographical Science, Beijing Normal University, Beijing 100875


MSC: P941.73;P534.63⁺2;P532

--> Received Date: 19 March 2018
Revised Date: 02 June 2018
Publish Date: 30 September 2018


摘要
摘要:选取毛乌素沙漠东南缘典型湖沼相沉积炭窑沟剖面，通过分析沉积序列粒度组成与粒度分布特征，结合AMS ¹⁴C年代数据，恢复了本区12.2 cal.ka B.P.以来的环境变化过程。结果显示：12.2 cal.ka B.P.之前沉积物较粗，以极细砂和细砂为主，粒度分布曲线与现代风成砂一致，为典型风成砂堆积，说明这一时期气候干旱，炭窑沟地区为沙漠环境；12.2~6.2 cal.ka B.P.堆积湖相沉积，粉砂和粘土含量增加，指示气候变湿，变为湖滨或浅湖环境；6.2~3.0 cal.ka B.P.发育泥炭，沉积物以粉砂为主，在细颗粒及300~500 μm处各有一个弱峰，说明这一时期气候持续好转，植被生长茂密，湖滨或浅湖变为湿地或沼泽；3.0 cal.ka B.P.之后沉积物平均粒径变粗，各组分随深度变化频繁，但粒度分布曲线主要表现为两种模式，一种为典型风成砂模式，一种为细颗粒显著增加的湖相沉积模式，指示这个时期气候总体变干，但期间经历了多次干湿变化。12.2 cal.ka B.P.以来毛乌素沙漠东南缘环境演化过程与季风边缘区气候变化有很好地一致性，与东亚季风变化也具有同步的变化规律，说明本区环境演化进程主要受到东亚季风的控制。
关键词: 毛乌素沙漠/
湖相沉积/
泥炭/
粒度/
环境变化

Abstract:The Mu Us Desert, located in the desert/loess transition zone and in the margin of the East Asian summer monsoon, is an ideal region for studying past environmental changes due to its sensitive climatic response. Fluvial-lacustrine sediments, peat and aeolian deposits have been used to explore past climate changes in this area. Compared to aeolian deposits, fluvial-lacustrine sediments and peat provide high resolution climatic or environmental information because of the relatively uniform accumulation rate in an aquatic or wetland environment.
In this paper, we obtained a 1050 cm-long lacustrine-peat sediment sequence(TYG section:37°43'10.73"N, 109°0'4.2"E) from the southeastern margin of Mu Us Desert. This section located on the first terrace of the Xuanhe River, a third-order tributary of the Yellow River. Subsamples were taken generally at an interval of 2 cm or 5 cm, and a total of 218 samples were collected for grain-size analysis using Malvern Mastersizer 2000. 11 samples were collected from the TYG section for Accelerator Mass Spectrometry(AMS) ¹⁴C dating at the Beta Analytic Radiocarbon Dating Laboratory. The dating results indicated the aeolian sand at 1050~834 cm accumulated before 12.2 cal.ka B.P., lacustrine sediments at 834~593 cm deposited from 12.2 cal.ka B.P. to 6.2 cal.ka B.P., peat at 593~317 cm developed from 6.2 cal.ka B.P. to 3.0 cal.ka B.P., and silt-sand at 317~11 cm accumulated after 3.0 cal.ka B.P.
We reconstructed regional environment changes since 12.2 cal.ka B.P. based on the grain-size characteristic of a high-resolution Holocene sequence of lacustrine-peat sediments. Our results indicate that before 12.2 cal.ka B.P., sediments sizes of TYG section were coarser than other periods, and main fractions of grain size were fine sand and sand, with the content of fine sand was 40.7%, distribution curve of grain size was bimodal. These results indicated climate was dry and this region was in a desert environment before 12.2 cal.ka B.P. From 12.2 cal.ka B.P. to 6.2 cal.ka B.P., lacustrine sediments occurred in the TYG section, accompanying with decreased sand fraction and increased fine grain-size fraction. The content of silt increased from 14.6% to 31.1%, and the content of clay changed from 1.7% to 4.5%.These evidences indicated that climate was wet and desert environment turned to shallow lake. Peat replaced lacustrine sediments in TYG section between 6.2 cal.ka B.P. and 3.0 cal.ka B.P. Clay and silt fraction content increased to 49.4%. The distribution curve of grain size was multimodal and there was a weak peak at 300~500 μm because coarse grains were more easily captured by the plants. These suggested that climate was optimum and shallow lake changed to swamp during this period in this region. Silt-sand accumulated and grain-size of sediments has two different distribution patterns since 3.0 cal.ka B.P. One was similar with that of aeolian sand, and the other was similar with that of lacustrine sediments. These evidences implied that climate turned to dry but it fluctuated frequently with several wet fluctuations since 3.0 cal.ka B.P. Comparison with other lacustrine sediments from surrounding areas shown that the environmental evolution in the southeastern margin of Mu Us Desert since 12.2 cal.ka B.P. was consistent with the climate changes in the margin of the East Asian summer monsoon, and was also synchronous with the changes of East Asian monsoon, indicating that the environmental evolution in the southeastern margin of Mu Us Desert was controlled by East Asian monsoon.
Key words:MuUs Desert/
lacustrine/
peat/
grain-size/
environmental changes



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