For use in LRRs K, L, M, N, P, Q, R, S, T, U, V, and Z.

A layer 10 cm (4 inches) thick, starting at a depth of 15 cm (6 inches) or less from the soil surface, with a matrix value of 3 or less and chroma of 1 or less. At least 70 percent of the visible soil particles must be masked with organic material when viewed through a 10x or 15x hand lens. The matrix color of the layer directly below the dark layer must have the same colors as described above or any color with a chroma of 2 or less.

User Notes: An undisturbed sample must be observed (fig. 26). Many wet soils have a ratio of about 50 percent soil particles that are masked with organic matter and about 50 percent unmasked soil particles, giving the soils a salt-and-pepper appearance. Where the organic matter coverage is less than 70 percent, the Dark Surface indicator does not occur. Observed without a hand lens, the masked sand particles appear to be closer to 100 percent masked with organic material when moist. Masked sand grains can disappear quickly if a soil has been drained or disturbed.