F21. Red Parent Material

For use in MLRA 127 of LRR N; MLRA 145 of LRR R; and MLRAs 147 and 148 of LRR S; for testing in all soils derived from red parent materials.

A layer derived from red parent materials (see Glossary) that is at least 10 cm (4 inches) thick, starting at a depth ≤25 cm (10 inches) from the soil surface with a hue of 7.5YR or redder.  The matrix has a value and chroma greater than 2 and less than or equal to 4.  The layer must contain 10 percent or more depletions and/or distinct or prominent redox concentrations occurring as soft masses or pore linings.  Redox depletions should differ in color by having:

a. A minimum difference of one value higher and one chroma lower than the matrix, or

b. Value of 4 or more and chroma of 2 or less.

User Notes:  This indicator was developed for use in areas of red parent material, such as residuum in the Piedmont Province Triassic lowlands section or the Paleozoic “red beds” of the Appalachian Mountains, and in alluvium or colluvium derived from these materials. This indicator may occur along the Red River (Arkansas and Louisiana). In glaciated areas, the indicator may form in glacial till, outwash, deltaic sediments, or glaciolacustrine sediments derived from similar parent materials in the area. Soils potentially derived from red parent materials should be evaluated to determine the Color Change Propensity Index (CCPI) and be shown to have CCPI values below 30 (Rabenhorst and Parikh, 2000). In landscapes where mixing or stratification of parent materials occur, it cannot be assumed that sediment overlying red parent material is derived solely from that parent material. The total percentage of all redox concentrations and redox depletions must add up to at least 10 percent to meet the threshold for this indicator.

This indicator is typically found at the boundary between hydric and non-hydric soils. Other, more common indicators may be found on the interior. It may be helpful to involve a soil scientist familiar with these soils to identify those soils that qualify for this indicator.