摘要
利用分形理论 ,研究了南极纳尔逊冰盖前缘发育的沉积物、风成沉积物及湖泊沉积物的粒度分布分形结构特征 .结果表明 :不同沉积环境下的沉积物粒度分形结构具有明显的差异 ,冰盖前缘沉积物具有显著的分形结构特征 ,而湖泊沉积物和风成沉积物不具有分形结构特征 ,这为识别南极地区松散沉积物沉积环境提供了一种新的判别依据 .对纳尔逊冰盖前缘沉积物粒度分维特征的研究结果表明 ,其粒度分布主要与冰川搬运的动力学过程有关 ,分维值的大小与当时形成沉积物的动力学过程、沉积环境、冰盖进退及古气候环境的演化密切相关 .
Grain-size distributions of sedimentary materials are widely used to glean information about sedimentary process and environment. The most common unit of measurement for such size distributions is weight of materials within a certain size range. In this paper, the method presented by Hooke et al. (1995) is applied to analyze size distribution. The grain-size distributions of the sediments from the margins of Nelson Ice Cap are presented as bivariate plots of log number of particles against log particle diameter. For comparison, the grain-size distributions of samples from eolian and lake sedimentary environments are also studied. It is shown that the fractal features of the sediments under different sedimentary environment display obvious difference. Periglacial sediments have remarkable fractal features, with fractal dimensions of approximate 2.9, similar to findings by Hooke and Iverson (1995) for the deforming tills collected from beneath modern glaciers. While the samples from lake sediments and eolian sediments do not have fractal size distribution. This can be used as new diagnostic criteria to discriminate the sedimentary environment for the sediments in Antarctica. The fractal features of the samples from the margin of Nelson Ice Cap have significant environmental implications. The fractal values of the periglacial sediments have a close relationship with mean grain size, standard deviation and hydrodynamic intensity. The geochemical characteristics of a series of sediments N1 and the surface textures of quartz grains in the sediments indicate that N1sediments are the products of glacial process, and have nothing to do with the chemical weathering. Further research suggests that the fractal dimensions of samples from the margin of ice sheet are the integrated results of glacial dynamic process, sedimentation environment and climatic environmental evolution. According to the changing trend of the fractal dimensions, it is possible to reconstruct the evolutionary history of the palaeoclimate environment and the advance/retreat of the ice sheet.
出处
《冰川冻土》
CSCD
北大核心
2003年第4期394-400,共7页
Journal of Glaciology and Geocryology
基金
国家自然科学基金项目 (40 0 76 0 32 )
中国科学院知识创新工程重大项目 (KZCX2 30 3)
科技部"十五"社会公益研究专项资金项目 (2 0 0 1DIA5 0 0 40 )资助
