Geospatial analysis linked verified problematic soils with associated geologic units and soil series, generating maps of RPM distribution.
Potential problematic RPM was identified in the Northeast and Mid-Atlantic, Great Lakes, South-central, and Desert Southwest-Western Mountains (problematic RPM regions herein), encompassing diverse groups of soils and parent materials.
Guidance was developed as early as 1996 to aid in the identification of wetlands in soils derived from RPM, with additional strategies described in recently published regional supplements to the USACE wetland delineation manual (USACE ) demonstrated that soils derived from red shales resisted color changes under both field and laboratory conditions compared with soils derived from the other formations within the same area of New Jersey.
Red soils from stratigraphically-related formations in Maryland and Connecticut also lacked prominent redoximorphic features despite highly-reducing conditions observed during field studies (Elless et al. While these case studies demonstrate that some red soils are problematic, the majority of red soils or soils derived from red-colored parent material readily form hydromorphic features under anaerobic conditions (Rabenhorst and Parikh ).
The F21 - Red Parent Material hydric soil field indicator requires (USDA-NRCS A layer derived from red parent materials that is at least 10 cm (4 in.) thick, starting at a depth ≤ 25 cm (10 in.) from the soil surface with a [Munsell] hue of 7.5YR or redder.
The matrix has a value and chroma greater than 2 and less than or equal to 4.change color) under reducing conditions was developed; entitled the Color Change Propensity Index (CCPI).The CCPI groups soils into three categories: 1) non-problematic RPM soils displaying no color change resistance (CCPI values In order to address hydric soil delineation challenges associated with problematic RPM soils, a field indicator of hydric soils was developed for use in areas containing RPM (F21 - Red Parent Material).Hydric soil identification utilizes diagnostic morphologic features, including iron transformations, resulting from anaerobic conditions.However, soils derived from some red parent materials (RPM) fail to develop characteristic hydric soils morphologies, confounding hydric soil and wetland delineation.Additionally, some problematic soils result from factors related to parent material characteristics.For example, soils derived from dark parent materials (e.g.Notably, the indicator has also been approved for testing across the United States in all soils derived from RPM (USDA-NRCS ).As a result, the F21 – RPM indicator can be applied in any soil identified as containing problematic RPM.The layer must contain 10% or more depletions and/or distinct or prominent concentrations occurring a soft masses or pore linings.Redox depletions should differ in color by having: The F21 - Red Parent Material hydric soil field indicator is approved for use in portions of the mid-Atlantic, New England, and Appalachian mountains including Major Land Resource Area (MLRA) 127 of Land Resource Region (LRR) N, MLRA 145 of LRR R, and MLRAs 147 and 148 of LRR S.