Which soil horizon, also known as the zone of accumulation, is enriched in clay, iron oxides, silica, carbonate, and other materials?

The B horizon, or subsoil, is often called the "zone of accumulation" where chemicals leached out of the A and E horizon accumulate. The word for this accumulation is illuviation. The B horizon has a lower organic matter content than than the topsoil and often has more clay.