Chromatic characteristics of sediments in the northern Kumtagh Desert and analysis of alternating light and dark landscapes on dune surfaces
The northern part of the Kumtagh Desert exhibits a dark surface color,ranging from brown black to grayish brown.Additionally,certain feather-like dunes often display contrasting patches of light and dark hues on their surfaces,which has emerged as one of the distinctive characteristics defining this desert.The origin of light and dark spots in sand grains was investigated by conducting field surveys from 45 geomorphic sampling sites in the northern Kumtagh Desertin late September to early October 2020 and 2021,75 groups of grain size analysis,39 groups of color grains(434 grain size samples)were identified visually,as well as 157 samples of sediment chroma were determined by colorimeter.The findings demonstrate a robust linear relationship between the visual colorimetric index(CI)and the measured luminance L* as well as yellowness b*,indicating their interchangeability in expressing both color and brightness levels of sediment.CI and L* exhibit close associations with particle color and size.The presence of black,gray,and brown hues can be attributed to the primary lithology of clasts and weathered attachments show a strong correlation with coarse rock debris,resulting in high chromaticity but low brightness.On the other hand,yellow and white tones primarily originate from light-colored rocks and minerals that are closely linked to fine particle sizes,leading to low chroma yet high brightness.The desert has obvious sedimentary stratification,in which parallel bedding is characterized by the largest particle size at the top and gradually decreasing downward,and has a major influence on the chromaticity of the dune surface.The variation in surface chroma of sand dunes is the outcome of peristaltic accumulation of coarse-grained rock debris and wind erosion transport of fine-grained minerals during the movement of sand particles.A slight relative change,ranging from 5％to 10％,in very coarse sand with high chroma-1.0～0 Φ or a mixture of very coarse sand and coarse sand-1.0～0.5 Φ can result in different shades of color spots appearing on adjacent areas of the dune surface.The present study can offer experimental models and data references to elucidate the origin and formation mechanism of surface color in sand dunes within the Kumtagh Desert and similar desert environments.
chrominancegrain sizeparallel beddinglight and dark patchesKumtagh Desert
万方数据
维普
