摘要
青藏高原东南缘干热河谷中广泛发育黄土或黄土状土,是解读中国西南季风、干热河谷环境演变与高原隆升关系的良好载体,但目前尚无关于其成因、形成时代和古气候意义的系统研究。通过对金沙江干热河谷华弹段中黄土状土的空间分布、粒度特征、化学风化指数以及沉积速率的分析,发现该区黄土状土拔河越高,粒径越小,沉积速率越低;结合前人物源示踪研究成果,证实黄土状土来源于金沙江谷底的河漫滩沉积和古堰塞湖沉积,局地山谷风环流为其提供搬运动力。磁性地层学分析显示黄土状土地层全为正极性,剖面中未出现B/M界线,结合光释光测年结果,确定金沙江干热河谷华弹段中的黄土状土形成于中更新世中期以来。通过与同河段的古堰塞湖沉积形成时代进行对比,发现黄土状土的形成时代稍晚于同河段古堰塞湖相沉积大量堆积的时代。金沙江河谷中黄土状土与古堰塞湖相沉积在时空上的紧密关联性表明,滑坡堰塞事件控制着金沙江干热河谷中黄土状土物源的丰富程度,是影响金沙江深切河谷中黄土状土形成与沉积过程的主要因素。黄土状土的粒度与化学风化指数结果表明358 ka BP以来,该段河谷中古环境气候发生过明显冷干-暖湿波动,并在冰期-间冰期尺度上响应全球气候变化。
Loess-like sediments are widely developed in the dry-hot valley of the Jinsha River,which is a good carrier for interpreting the southwest monsoon and the environmental evolution of the dry-hot valley of the Jinsha River.However,its genesis and formation time are still unclear.Through the analysis of the grain size and deposition rate of loess-like sediments at different altitudes in the Huatan section of the Jinsha River Valley,it is found that the higher the altitude,the smaller the particle size and the lower the deposition rate of the loess-like sediment.Combined with previous research results,it is further confirmed that the loess-like sediments is a nearsource aeolian deposit derived from the floodplain deposition and the ancient dammed lake deposits at the bottom of Jinsha River Valley,and the local valley wind circulation in Jinsha River Valley provides transportation power for it.Through optical luminescence dating and magnetostratigraphic analysis,it is determined that the loess-like sediments in the dry-hot valley of the Huatan section of the Jinsha River Valley was formed in the middle of the Middle Pleistocene,which approximately consistent with or later than the time of massive accumulation of ancient dammed lake deposits in the valley.The consistency of the temporal and spatial distribution of the loess-like sediments and the ancient dammed lake deposits in the Jinsha River Valley indicates that the landslide damming event controls the provenance of the loess-like sediments in the dry-hot valley of the Jinsha River,and is one of the main factors affecting the deposition process of the loess-like sediments.The grain size and chemical weathering index of loess-like sediments indicate that the valley wind,environment and climate have changed significantly since 358 ka BP,and responded to global climate change on the glacial-interglacial scale.In the future,it is necessary to strengthen the study on the relationship between loess-like sediments and ancient dammed lake in deep valleys of southwest China.
作者
刘芬良
高红山
潘保田
李宗盟
Liu Fenliang;Gao Hongshan;Pan Baotian;Li Zongmeng(Department of Geographic Information System Science,Hunan City University,Yiyang 413000,Hunan,China;Ministry of Education Key Laboratory of Western China's Environmental Systems/College of Earth and Environmental Sciences,Lanzhou University,Lanzhou 730000,China;School of Geographic Sciences,Xinyang Normal University,Xinyang 464000,Henan,China)
出处
《中国沙漠》
CSCD
北大核心
2022年第4期60-70,共11页
Journal of Desert Research
基金
第二次青藏高原综合科学考察研究项目(2019QZKK0205)
国家自然科学基金项目(42101005)
湖南省自然科学基金项目(2021JJ40023)
湖南省教育厅优秀青年项目(20B106)。
关键词
黄土状土
成因
年代
华弹
金沙江
loess-like sediment
genesis
formation time
Huatan
Jinsha River