李育,,
张新中,
韩琴,
徐玲梅,
叶旺庭
兰州大学资源环境学院, 甘肃 兰州 730000
基金项目: 国家自然科学基金项目（批准号：41822708）、中国科学院（A类）战略性先导科技专项项目（批准号：XDA20100102）和科技部、中国科学院第二次青藏高原综合科学考察研究项目（批准号：2019QZKK0202）共同资助
详细信息
作者简介: 陈大伟, 男, 24岁, 硕士研究生, 内流河流域古环境研究, E-mail:lansedreams@163.com
通讯作者: 李育, E-mail:liyu@lzu.edu.cn
中图分类号: P931.1;P512.2收稿日期:2019-09-11
修回日期:2020-01-21
刊出日期:2020-09-30
Study on grain size indicator of surface soil and terminal lake sediments in closed basins over Qilian Mountains
Chen Dawei,Li Yu,,
Zhang Xinzhong,
Han Qin,
Xu Lingmei,
Ye Wangting
College of Earth and Environmental Sciences, Lanzhou University, Lanzhou 730000, Gansu
More Information
Corresponding author: Li Yu,E-mail:liyu@lzu.edu.cn
MSC: P931.1;P512.2--> Received Date: 11 September 2019
Revised Date: 21 January 2020
Publish Date: 30 September 2020
摘要
摘要:通过对祁连山地区典型内流河——石羊河、丰乐河、石油河和布哈河流域表土及终端湖全新世剖面沉积物中粒度指标的分析和对比，结果表明：1）流域表土粒径随海拔变化具有明显的空间分异特征，大致以河流出山口海拔为界分为上下游两部分，除石油河外，上游以粉砂组分为主，粒度频率曲线表现为河流沉积的双峰特征，粒径波动较小并随海拔有降低趋势，反映河流初始水动力较强并逐渐减弱；下游以砂组分为主，粒度频率曲线具有风成沉积特征，指示干旱化趋势，粒径变化幅度和频率大，表明受人类活动影响强烈；2）终端湖剖面沉积物粒度显示了全新世以来复杂的干湿变化，在约3 cal.ka B.P.之后均出现粒径增大波动增大的现象，指示不同程度的干旱化，在1~3 cal.ka B.P.之间出现人类活动的影响并逐渐加剧；3）基于流域表土粒度指标现代过程分析表明祁连山内流河流域终端湖剖面粒度指标可以在一定程度上指示流域干湿变化并识别人类活动强度，区域环境在长期干旱化的背景下受到人类活动的强烈干扰。
关键词: 祁连山/
内流河/
沉积物/
粒度/
环境变化
Abstract:Four typical closed basins of Qilian Mountains, Shiyang River basin, Fengle River basin, Shiyou River basin and Buha River basin are selected as the study areas. Surface soil and 30 cm underground soil samples along both sides of the river are collected to analyze the grain size characteristics of these regions. Median grain size and average grain size of the soil samples, combined with the terminal lakes records of these basins (including median grain size, average grain size, and grain size composition) are used to analyze the characteristics of the environmental changes in these four river basins during the Holocene. The results show:
(1) Soil grain size in these basins has obvious spatial differentiation along with changing altitudes, which roughly divides the basin into two parts of the upstream and downstream depending on the position of the river flowing out of the mountain. Except for the Shiyou river basin, silt component takes advantage in the upstream, and the grain size frequency curve shows the double peak characteristics of river deposition with low fluctuation. However, sand component prevails in the downstream parts, the grain size frequency curve has the characteristics of aeolian deposition with more and higher fluctuation, indicating strong influence by human activities;
(2) The grain size records from terminal lakes show complex dry-wet changes during the Holocene. However, a consistent change that the mean grain size and fluctuation both increased since about 3000 years ago in these records is confirmed. The increase of grain size indicates that the terminal lake area has experienced different aridity process, and the fluctuation anomaly indicates that the deposition process may be affected by modern human activities which gradually increases between 1 cal.ka B.P. and 3 cal.ka B.P.;
(3) The modern process analysis shows that the grain size of terminal lake sections in the closed basins over Qilian mountains can indicate the change of dry and wet climate in the past and identify the intensity of human activities, and the regional environment is strongly disturbed by human activities under the background of long-term drought. In the future, the process of aridity will continue, and the extent and intensity of human activities will be further enhanced.
Key words:Qilian Mountains/
interior river/
sediment/
grain size/
environmental change
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