香山北麓末次冰期风成沉积物粒度的空间变化研究

黄土的粒度被广泛地用作气候变化特别是冬季风强度变化和沙漠范围变迁的替代性指标。对宁夏中部陇西黄土高原北缘的香山北麓从北向南的七个样点末次冰期以来风成堆积物粒度的系统分析表明,在末次冰期中,影响沉积物粒度的因素主要是距离源区的远近和海拔高度,而风力强度基本相似,后期风化作用较小,可以忽视。随着距离现代沙漠南缘距离的增加和海拔高度的增加,沉积物的粒度都会相应减小。通过数学统计处理后的结果显示,在较小的空间范围内,海拔高度的影响比源区距离更重要。

Study on Grain-size of the Aeolian Sediments in the Northern Fringe of Xiangshan Mountain During the Last Glacial

Grain size is the most fundamental property of sediment particles,affecting their entrainment,transport and deposition.The aeolian sand and dust has been taken as an important proxy of expansion and contraction of the desert during geological period.The signals of the desert evolution were well preserved in the aeolian deposits on the margin of the desert,which are effective to reconstruct the desert expansion and contraction.According to the dominant wind direction,generally NW-SE,the authors systematically studied 7 sections of Malan loess in the Northern fringe of Xiangshan Mountain during the Last Glacial period.Detailed granular analyses show the properties of temporal and spatial of the Malan loess,and reducing of the percentage of the sand from northwest to southeast.The study indicates a new linear correlation model of sand percentage with altitude and distance,and the altitude has a more influence to the sand fraction.