Grain size Characteristics and Evolution of Core Sedimentary Environment in the Houtao Plain Reach of the Yellow River
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摘要: 基于现代地表不同沉积环境组成物质的粒度组合特征,采用粒度特征的多种图解方法建立了沉积物粒度特征与沉积环境之间的对应关系,进而对黄河后套平原段2个深约20 m的钻孔岩芯进行了沉积相的解译。研究结果表明,晚第四纪该区钻孔沉积环境经历了多次相变,但仍以河床相为主,分别占到68%和57%,说明黄河在该区存在多个沉积旋回,摆动频繁;而沙漠相仅在钻孔DKZ04顶部出现,指示了磴口以西乌兰布和北缘连续的沙漠景观出现的时代较晚,可能是2 000年以来受黄河河道向南迁移废弃导致的湖泊干涸和荒漠化以及大规模人类活动导致的土地荒漠化共同作用而形成的。Abstract: Sediment grain size parameters provide important information about depositional processes and environments because the size range,mixing and sorting of sediment populations vary systematically in response to the sedimentation processes,dynamics and provenance. Thus the analysis of textural parameters is the basis for determining the process/response behavior of individual sedimentary units and their environment. Grain size distribution distinguishes the surface sedimentary environment in the Houtao plain,and was therefore adopted in this sedimentary facies interpretation of two drill cores from the Houtao plain reach of the Yellow River. The results show that the sedimentary environment underwent many transformations,dominated by fluvial channel facies(68% in Core DKZ04, and 57% in Core HDZ04). This indicates that the channel of the Yellow River has experienced extensive migration in this region. In addition,since aeolian sand appears only at the top of Core DKZ04,we speculate that the present desert landform of the northern Ulan Buh Desert started to form only 2 000 years ago,probably triggered by river migration and large-scale human activity.
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Key words:
- grain size characteristic /
- sedimentary facies /
- Houtao plain /
- Yellow River
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