For use in LRRs K, L and U.

A layer of marl with value of 5 or more and chroma of 2 or less starting at a depth of 10 cm (4 inches) or less from the soil surface (fig. 36).

User Notes: Marl is a limnic material deposited in water by precipitation of calcium carbonate by algae as defined in “Soil Taxonomy” (Soil Survey Staff, 1999). It has a Munsell value of 5 or more and reacts with dilute hydrochloric acid to evolve carbon dioxide. 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 of 10 cm (4 inches) or less from the soil surface. Normally, this indicator occurs at the soil surface. There is no thickness requirement to meet this indicator.