Redoximorphic features: Relic (left side) vs Contemporary (right side) RMFs
Redoximorphic features (RMFs) consist of color patterns in a soil that are caused by loss (depletion) or gain (concentration) of pigment compared to the matrix color, formed by oxidation/reduction of iron and/or manganese coupled with their removal, translocation, or accrual; or a soil matrix color controlled by the presence of iron. The composition and responsible formation processes for a soil color or color pattern must be known or inferred before it can be described as an RMF.
These color separations are used by soil scientists to document the presence of an active water table, both epi- and endo- saturation. However, these changes in color may be an indication of a much older environment in which the features formed, not current saturation and reduction processes.
One technique that helps determine if the feature is contemporary is the sharpness of the feature boundary. A color transition that is gradual or diffuse is associated with contemporary aquic conditions. Transitions that are clear or sharp and more distinct are commonly associated with relic or ancient soil environments. In addition, if the concentrations are relic they tend to exhibit brittleness, although plinthite is commonly brittle even when present in a contemporary aquic regime.
Color separations observed in the soil on the left (L) were thought to be relic and not due to active oxidation and reduction processes, whereas the color separations observed in the soil on the right (R) were thought to be contemporary and the result of active oxidation and reduction processes with a seasonal water table.
For more information about describing and sampling soils, visit:
www.nrcs.usda.gov/resources/guides-and-instructions/field...
or Chapter 3 of the Soil Survey manual:
www.nrcs.usda.gov/sites/default/files/2022-09/The-Soil-Su...
For additional information on "How to Use the Field Book for Describing and Sampling Soils" (video reference), visit:
www.youtube.com/watch?v=e_hQaXV7MpM
For additional information about soil classification using USDA-NRCS Soil Taxonomy, visit:
www.nrcs.usda.gov/resources/guides-and-instructions/keys-...
or;
www.nrcs.usda.gov/resources/guides-and-instructions/soil-...
Redoximorphic features: Relic (left side) vs Contemporary (right side) RMFs
Redoximorphic features (RMFs) consist of color patterns in a soil that are caused by loss (depletion) or gain (concentration) of pigment compared to the matrix color, formed by oxidation/reduction of iron and/or manganese coupled with their removal, translocation, or accrual; or a soil matrix color controlled by the presence of iron. The composition and responsible formation processes for a soil color or color pattern must be known or inferred before it can be described as an RMF.
These color separations are used by soil scientists to document the presence of an active water table, both epi- and endo- saturation. However, these changes in color may be an indication of a much older environment in which the features formed, not current saturation and reduction processes.
One technique that helps determine if the feature is contemporary is the sharpness of the feature boundary. A color transition that is gradual or diffuse is associated with contemporary aquic conditions. Transitions that are clear or sharp and more distinct are commonly associated with relic or ancient soil environments. In addition, if the concentrations are relic they tend to exhibit brittleness, although plinthite is commonly brittle even when present in a contemporary aquic regime.
Color separations observed in the soil on the left (L) were thought to be relic and not due to active oxidation and reduction processes, whereas the color separations observed in the soil on the right (R) were thought to be contemporary and the result of active oxidation and reduction processes with a seasonal water table.
For more information about describing and sampling soils, visit:
www.nrcs.usda.gov/resources/guides-and-instructions/field...
or Chapter 3 of the Soil Survey manual:
www.nrcs.usda.gov/sites/default/files/2022-09/The-Soil-Su...
For additional information on "How to Use the Field Book for Describing and Sampling Soils" (video reference), visit:
www.youtube.com/watch?v=e_hQaXV7MpM
For additional information about soil classification using USDA-NRCS Soil Taxonomy, visit:
www.nrcs.usda.gov/resources/guides-and-instructions/keys-...
or;
www.nrcs.usda.gov/resources/guides-and-instructions/soil-...