Final answer:
The Bt horizon in a soil profile indicates a concentration of clay particles and other materials like iron and aluminum that have been carried down from the A horizon, or topsoil.
Step-by-step explanation:
A Bt Horizon Concentration
The Bt horizon indicates a concentration of clay particles, along with translocated materials like silicate clay, iron, aluminum, or a combination of these, which have moved downward from the upper layers of soil. This horizon forms part of the subsoil and is characterized by an accumulation of mostly fine materials.
Through processes such as rainwater percolation, these particles are washed down from the A horizon, or topsoil, consequently enriching the B horizon with finer materials and often making it denser than the layers above.
In the soil profile, each layer, or horizon, has distinct physical and chemical properties that are used for soil classification. In summary, the Bt horizon represents a subsoil layer enriched with fine particulates such as clay, which have been transported from the A horizon, or topsoil.