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 10 cm (4 inches) or more thick, starting at a depth of 25 cm (10 Inches) or less from the soil surface with a hue of 7.5YR or redder. The matrix has a value and chroma of more than 2 and 4 or less. The layer must contain 10 or more percent depletions and/or distinct or prominent concentrations occurring as soft masses or pore linings. Redox depletions should differ in color by having:
1. a minimum difference of one value higher and one chroma lower than the matrix, or
2. value of 4 or more and chroma of 2 or less than the matrix (fig. 41).
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 (CPPI) and be shown to have CCPI values less than 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 10 percent or more 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 (fig. 42). Mack et al. (2019) provides maps of soils and geologic features associated with red parent materials. It may be helpful to involve a soil scientist familiar with these soils to identify those soils that qualify for this indicator.