C horizon

noun
1.
the layer in a soil profile below the B horizon and immediately above the bedrock, consisting chiefly of weathered, partially decomposed rock.
Origin
1930-35
British Dictionary definitions for C horizon

C horizon

noun
1.
the layer of a soil profile immediately below the B horizon and above the bedrock, composed of weathered rock little affected by soil-forming processes
C horizon in Science
C horizon  
In ABC soil, the lowermost zone, consisting mainly of unconsolidated, weathered rock fragments. By comparison with the A and B horizons, the C horizon is relatively unaffected by the processes of soil formation and therefore does not exhibit as much internal layering.