Melanic horizon
The Melanic/Melacic horizons are the next step down from the Humose horizons in terms of the organic carbon level of black surface soils. Melanic horizons are conceptually similar to the outstanding soils with Mollic epipedons in Soil Taxonomy (Mollisols). Because of the organic matter, melanic horizons usually have superior qualities with better structure, pH, infiltration and water holding capacity. If the surface soil does not have reasonable natural structure (moderate to strong) it won't qualify as Melanic, even if it is black. Because they are commonly cropped, soils with Melanic horizons may lose their natural structure and become cloddy due to compaction and smearing. To confidently determine that a Melanic horizon is present, inspection at undisturbed sites are preferred.
Melanic horizon in the upper part of this profile.
Photo credit: tba