illuviation

n.
The deposition in an underlying soil layer of colloids, soluble salts, and mineral particles leached out of an overlying soil layer.

[illuvial, resulting from illuviation (IN-² + -luvial, relating to the action of flowing water , as in ALLUVIAL) + -ATION.]

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The downward translocation from the A horizon and subsequent precipitation in the B horizon of clay-sized particles in a soil. Hence illuvial horizon; the B horizon, in which there is redeposition or entrapment of matter brought down from above.