For use in LRRs K, L and U.

A layer of marl with value of 5 or more and chroma 2 or less starting at a depth ≤10 cm (4 inches) from the soil surface. 

User Notes: Marl is a limnic material deposited in water by precipitation of CaCO3 by algae as defined in Soil Taxonomy (Soil Survey Staff, 1999). It has a Munsell value of 5 or more and reacts with dilute HCl to evolve CO2. Marl is not the carbonatic substrate material associated with limestone bedrock. Some soils have materials with all of the properties of marl, except for the required Munsell value. These soils are hydric if the required value is present at a depth ≤10 cm (4 inches) from the soil surface. Normally, this indicator occurs at the soil surface.