Soils

Mineral horizon below an O, A, or E horizon. The B horizon show evidences of soil forming processes which distinguish it from the parent material of soil (underlying C horizon). The distinctive characteristics can be: (1) accumulation (iluviation) of clay, sesquioxides, humus, or a combination of these; (2) granular, prismatic, or blocky structure; (3) redder [...]

The mineral horizon at or near the surface in which an accumulation of humified organic matter is mixed with the mineral material. Also, any ploughed or disturbed surface layer.