青海湖南岸二郎剑—黑马河地区源-汇体系特征及控制因素

Characteristics and control factors of the source-to-sink system in the Erlangjian-Heimahe area on the south bank of Qinghai Lake

通过野外观察、粒度和遥感资料的综合分析,详尽描述了青海湖二郎剑—黑马河地区从物源区到沉积区的地表沉积动力过程。青海湖南岸现代前滨亚相的湖滩沉积分为滩脊、滩脊间、滩后席状砂和滩后潟湖。以现代滨岸相的研究为基础,结合两个典型剖面,深入分析单一期次和多期次湖滩的沉积特征,建立了多期次湖滩的沉积演化模式,并对比分析古今滨岸相的沉积特征。青海湖南岸源-汇沉积体系的控制因素包括地形地貌、物源区的岩性特征、水系、植被类型和覆盖度、风场、波浪、湖流、湖平面升降等。山地地貌影响着水系分布、区域风场和沉积物搬运距离,湖底地貌影响着湖流的环流方向。被侵蚀和搬运的沉积物类型取决于物源区的岩性特征。植被类型和覆盖度决定着物源区沉积物的稳定性。水系的径流量和沉积物的供给类型及季节性的气候变化影响着沉积物搬运过程。区域上的风场特征与降雨量存在着密切关联,从而间接影响植被类型和覆盖度。波浪控制着单期滩体的形成。湖平面升降影响着可容纳空间的变化,从而控制着多期滩体的形成。青海湖南岸二郎剑—黑马河地区现代沉积体系的形成与展布除了受源-汇体系控制,还与风向和风力有关,具有明显的强物源、背风的特征,表现为强物源背风体系。

Through the comprehensive analysis of field observation,granularity and remote sensing data,this paper detailedly describes the dynamic surface sediment process from the provenance to the sedimentary area in the Erlangjian-Heimahe area of Qinghai Lake.The lake beach deposits of the modern foreshore subfacies on the south bank of Qinghai Lake are divided into beach ridge,inter-beach ridge,back-beach sheet sand,and back-beach lagoon.Based on the study of modern shore facies,in combination with two typical sections,this paper performs an in-depth analysis on the single-stage and multi-stage sedimentary characteristics of lake beach deposits,establishes a sedimentary evolution model of multi-stage lake beach,and compares and analyzes the sedimentary characteristics of ancient and modern shore facies.The controlling factors of the source-to-sink sedimentary system of the south bank of Qinghai Lake include topography and landform,lithological characteristics of the provenance,water system,vegetation type and coverage,wind field,wave,lake current,and lake level fluctuation.The distribution of water system,regional wind field and the transport distance of sediments are affected by mountain landforms,and the circulation direction of lake current is impacted by sublacustrine landforms.The types of the sediments eroded and transported depend on the lithological characteristics of the provenance.The stability of sediments in the provenance is determined by vegetation type and coverage.The transport process of sediments is influenced by the runoff of water system,the supply type of sediments and seasonal climate changes.The characteristics of the regional wind field are closely related to rainfall,which indirectly affects the vegetation type and coverage.The formation of single-stage beach body is controlled by wave.Lake level fluctuation affects the change of accommodation space,thereby controlling the formation of multi-stage beach body.In addition to being controlled by the source-to-sink system,the formation and distribution of the modern sedimentary system in the Erlangjian-Heimahe area on the south bank of Qinghai Lake is also related to wind direction and wind force,showing the obvious characteristics of strong source and leeward,manifested as a strong-source leeward system.