Characteristics of collapsible red soil in Northeast Thailand

We analyzed the characteristics of red soils that are often considered collapsible soils. In this study, we examined the depositional environment and lithologic characteristics, analyzed stratigraphy, and conducted mechanical sieve, X-ray fluorescence, X-Ray diffraction, scanning electron microscope, X-ray fluorescence analyses and optically stimulated luminescence dating. The samples were collected from the gravel pits to examine and reveal details of their depositional processes. The abrupt particle size change in the overlying soil formed a pseudo-disconformity with the subjacent gravel bed. The soil was unstratified with granule gravels scattered throughout the soil layer. The soil consisted of mostly sand (~70%), with minor silt and clay contents (~30%); thus, the soil was classified as silty sand. The soil samples contained a large amount of silicon, a high percentage of quartz. V-shaped micro textures represented percussion and abrasion mechanisms on the surface of individual grains, suggesting transport by fluvial processes. The deposition occurred during the Late Pleistocene, and the absence of desert environment suggested different conditions than those associated with aeolian deposition. Consequently, the lithology, physical and chemical properties, and chronology were consistent with termite mounding, which plays an important role in the upward transportation of small particles and causes large sediments to descend.