Re: Entisols: "C horizon on topsoil"

Since there is enrichment of carbon in the surface horizon, I would name it an A horizon despite absence of soil structure. There is little chance for moderate structure to form in the absence of clay, but the carbon may allow some very weak structural units to form. I would not consider the absence of soil structure to be the same as the structure of the rock or sediment. I would only consider the surface to be a C horizon if it had thin layering from eolian or fluvial deposition in half or more of the volume.