Creep of aeolian sediments on the surface of granule ripples and its geomorphological significance
Creep is one of the three fundamental forms of blown sand movement and is currently a less-studied research area.Granule ripples,as a unique aeolian landform,are characterized by surfaces covered with coarse particles and composed of bimodal sediments.Their formation and evolution are closely related to creep move-ment,and the scientific community's understanding of their morphodynamic processes is quite limited.There-fore,this paper uses granule ripples as a study subject to investigate the laws of creep movement and explore their geomorphological significance.The research was conducted in the Sanlunsha area of the northern Kumtagh Des-ert,using a novel creep sand trap.We conducted 10 continuous in-situ observations over a period of 14 months.The results indicate that the creep sand flux on the surface of granule ripples ranges from 0.047 g·cm-2·min-1 to 0.352 g·cm-2·min-1,with significant seasonal variations.The grain size distribution of the creep material is bimod-al,well-sorted,coarse-skewed,and has platy kurtosis.The content of medium and fine sand can reach 85％,while coarse sand and larger particles account for more than 10％.Creep sand fluxes exhibited clear variations de-pending on grain size,with the highest fluxes occurring in medium and fine sands,and measurably lower fluxes in very coarse sands and very fine gravels.There is a correlation between the creep sand flux and the average sand-driving wind speed.The strongest creep sand flux occurred during summer dust storms,while the weakest occurred in winter.In addition to wind conditions,the grain size characteristics of the sediments and the supply of sand from different directions also influence the creep sand flux and material composition.From a sedimento-logical perspective,the creep movement on the surface of granule ripples significantly contributes to the forma-tion of their internal poured-in structures and coarse-fine interlayered forest laminations.This research provides new insights into the physical processes of wind-driven creep and the evolution of granule ripple bedforms.The traditional method of classifying creep based on grain size is questionable,and a more in-depth study of the mechanisms of creep movement and its geomorphological significance is necessary.
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