中国北方东部沙质荒漠化的地学观
Geological views on the sandy desertification of the east part of northern China
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摘要: 中国北方东部的土地荒漠化主要受新构造运动以来的构造-沉积特征、青藏高原隆升所引起的全球气候变化、尤其是亚洲季风等地质背景控制。北方东部沙质荒漠化区域地质分类,按其成因可分为就地起沙型、风沙型和土地粗粒化型等3种类型。其中,就地起沙型沙质荒漠化主要分布在东部毛乌素、科尔沁、浑善达克、呼伦贝尔等沙地内,流经这些沙地的古河道,广泛发育河湖相砂质沉积物以及以砂质沉积物为母质的土壤分布区。风沙型沙质荒漠化主要分布在上述沙地的边缘地带,如毛乌素沙地以南的覆沙黄土区等。土地粗化主要分布在内蒙古锡林郭勒草原-河北坝上草原,其土壤类型多为含砾沙土,其土壤母质为基岩风化壳、残坡积或冲洪积物。荒漠化发展趋势上,尽管就地起沙型沙质荒漠化在毛乌素、科尔沁和浑善达克沙地的局部地区均有所逆转,但总体上,在北方广大地区,主要以地表土壤粗化为主的荒漠化和风沙型荒漠化等均有不同程度的扩大。上述不同类型的沙质荒漠化,总体上受地质背景控制。其中,第四纪以来的构造-沉积特征控制着不同类型荒漠化的区域分布,气候变化控制着荒漠化的进程,人类活动则是在上述背景的基础上进行。Abstract: Land desertification of the east part of Northern China is mainly controlled by the geological backgrounds such as the tecto-sedimentary characteristics, global climatic changes, especially the monsoon current in east Asia. The regional geologic subdivisions of sandy desertification here could be divided into three types, which are termed as the localized type, the windblown type and the coarse-grained desertification type. Localized sandy desertification is mainly distributed over the areas of sands and deserts of which are MuUs Shadi,Horqin Shadi,Hun shandake Shadi and Hulun Buir Shadi,areas of paleochannels which p a ssed through these sands and deserts,the areas in which fluviatile and lacustrine sandy sedimentaries are widely spread,and the areas in which soil is developed on sandy sediments as well. The windb lown sandy desertification is distributed mainly at the edge of above deserts,such as sand-covered loess areas at the south of MuUs Shadi desert.