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Plinthite Characterization in Selected Southern Coastal Plain Soils
Author(s) -
Wood B. W.,
Perkins H. F.
Publication year - 1976
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1976.03615995004000010038x
Subject(s) - goethite , hematite , soil water , mineralogy , kaolinite , geology , quartz , amorphous solid , soil horizon , iron oxide , pedogenesis , horizon , soil science , chemistry , paleontology , physics , organic chemistry , adsorption , astronomy
Samples of plinthic horizons from five soil series were collected in the Southern Coastal Plains Province of Georgia. Plinthite and various colors of soil material in each horizon were separated and analyzed for particle size distribution, Fe 2 O 3 content, and mineralogy. Iron segregation is greater in plinthic than nonplinthic soil formations in subsurface horizons. In the upper part of B2t horizons where plinthite is nearest the surface, Fe is present as amorphous hydrated oxides and goethite giving the soil matrix a brownish‐yellow color. In the plinthite, there is a higher Fe content than in surrounding non‐plinthic soil and the Fe is present as the dehydrated oxide hematite in addition to the amorphous hydrated oxides and goethite. The lower part of the B2t horizon is composed of three color phases in which the Fe content as well as the form of Fe differs. In the pale‐colored soil (white, pale yellow), total Fe is relatively low. Iron occurs in greater amounts in the forms of goethite and amorphous compounds in the brownish yellow soil material. Plinthite has the highest Fe content which occurs as hematite, goethite, and amorphous hydrated oxides. Particle size distribution varies within plinthic horizons. Nonplinthic soil materials have higher percentages of <2µm particles than was found in plinthite. Kaolinite in the clay fraction of plinthite is in a more disordered crystalline state than in the matrix soil. The silt fraction of the soil matrix contains quartz in the pale‐colored soil and quartz and goethite in the yellow soil. Silt fractions of plinthite contain quartz, hematite, and goethite. The coarser texture of the plinthic material appears to be a result of destruction of kaolinite and crystal growth of Fe compounds. The end product of this process is hardened ironstone nodules or septaria which contain quartz, hematite, goethite, and weakly crystalline kaolinite.