Morphology and genesis of silt and clay coatings in the vesicular layerof a desert loam soil

The microscopic and submicroscopic characteristics of the vesicles in a Desert Loam (Haplic Durargid) soil were examined. The surface roughness of the vesicles depended on the texture of the material in which they formed. Plate-like silt and coarse clay particles on the vesicle surface were strongly oriented having a pavement-like appearance. Silt and clay coatings lined many of the vesicles and interconnected channels. Many vesicles occurred in clusters and contained layered coatings of different thickness:claycoatings up to 200 pm, silt coatings up to 300 pm, and composite coatings up to 1 mm. Some radially cracked claycoatings also contained silt depositions within the cracks. The probable genesis of the claycoatings involves the translocation of clay particles from an external source, through the raindrop-disturbed surface layer, and around entrapped air bubbles within vesicles. The morphology of the coating' indicates that the vesicles in this soil layer have considerable durability.