LOCATION MCFAIN ILEstablished Series
TAXONOMIC CLASS: Clayey over loamy, smectitic over mixed, superactive, mesic Fluvaquentic Endoaquolls
TYPICAL PEDON: McFain silty clay - slightly depressional, on a gently undulating flood plain in a cultivated field at an elevation of 418 feet above mean sea level. (Colors are for moist soil unless otherwise stated.)
Ap--0 to 6 inches; very dark gray (10YR 3/1) silty clay, dark gray (10YR 4/1) dry; moderate medium subangular blocky structure parting to weak fine granular; friable; common very fine roots; few thin sand lenses and few sand depletions on faces of peds; few large clam shell fragments on the soil surface; about 48 percent clay; neutral; clear smooth boundary.
A--6 to 15 inches; very dark gray (2.5Y 3/1) silty clay, dark gray (2.5Y 4/1) dry; strong fine and medium angular blocky structure; firm; common very fine roots; few fine vesicular pores; many faint very dark gray (2.5Y 3/1) pressure faces on faces of peds; very few sand depletions on faces of peds; about 45 percent clay; neutral; abrupt smooth boundary. (Combined thickness of the A horizon is 10 to 20 inches.)
2Btg--15 to 30 inches; dark gray (2.5Y 4/1) silt loam low in sand; moderate fine prismatic structure parting to moderate fine subangular blocky; friable; few very fine roots; few fine vesicular pores; common continuous distinct very dark gray (10YR 3/1) organo-clay films on faces of peds; common fine prominent irregular strong brown (7.5YR 5/6) masses of iron accumulation in the matrix; about 24 percent clay; slightly alkaline; clear smooth boundary.
2Btkg1--30 to 42 inches; gray (2.5Y 6/1) stratified silt loam and very fine sandy loam; weak fine subangular blocky structure; friable; few very fine roots; few continuous distinct very dark gray (10YR 3/1) organo-clay films lining root traces; common fine distinct light olive brown (2.5Y 5/4) masses of iron accumulation in the matrix; common fine and medium white (10YR 8/1) shell fragments of mollusks; about 20 percent clay; strongly effervescent; slightly alkaline; clear smooth boundary.
2Btkg2--42 to 56 inches; gray (2.5Y 5/1) stratified silt loam and very fine sandy loam; weak medium subangular blocky structure; friable; few very fine roots; few continuous distinct very dark gray (10YR 3/1) organo-clay films lining root traces; few faint patchy dark gray (2.5Y 4/1) clay films on vertical faces of peds; common fine distinct light olive brown (2.5Y 5/4) masses of iron accumulation in the matrix; few fine white (10YR 8/1) shell fragments of mollusks; about 23 percent clay; strongly effervescent; slightly alkaline; gradual smooth boundary. (Combined thickness of the 2Btg and 2Btkg horizons is 30 to 50 inches.)
2BCtg--56 to 66 inches; gray (2.5Y 5/1) silt loam high in very fine sand; weak coarse subangular blocky structure; friable; few very fine roots; few medium vesicular pores; few continuous distinct organo-clay films lining root traces; many medium and coarse prominent yellowish brown (10YR 5/6) masses of iron accumulation in the matrix; common fine and medium irregular strong brown (7.5YR 4/6) masses of iron-manganese accumulation with diffuse strong brown (7.5YR 5/6) boundaries; about 26 percent clay; slightly effervescent; slightly alkaline; gradual smooth boundary. (0 to 12 inches thick)
2Cg--66 to 80 inches; gray (2.5Y 5/1) silty clay loam high in very fine sand; massive; firm; common medium and coarse prominent yellowish brown (10YR 5/6) masses of iron accumulation in the matrix; about 28 percent clay; slightly effervescent; slightly alkaline.
TYPE LOCATION: Jersey County, Illinois; about 5 miles west of Fieldon; approximately 215 feet north and 618 feet west of the southeast corner of sec. 30, T. 8 N., R. 13 W.; USGS Nutwood, IL. topographic quadrangle; lat. 39 degrees 6 minutes 30 seconds N. and long. 90 degrees 34 minutes 45 seconds W.
RANGE IN CHARACTERISTICS: Depth to the base of soil development is 40 to more than 80 inches. Thickness of the mollic epipedon is 10 to 20 inches, and extends into the B horizon in some pedons. Depth to the loamy 2B horizon is 15 to 30 inches. The upper part of the particle-size control section (slackwater sediments) averages 35 to 50 percent clay and less than 15 percent sand. The lower part of the particle-size control section (loamy or sandy alluvium) contains less clay and more sand than the upper slackwater sediments.
The upper part of the series control section (Ap and A) has hue of 10YR, 2.5Y, or is neutral; value of 2 or 3 (3 to 5 dry); and chroma of 0 or 1. Texture typically is silt clay but includes silty clay loam in some pedons. An silt loam overwash phase is recognized. Clay content averages 35 to 50 percent and sand content is less than 15 percent. Reaction is slightly acid to slightly alkaline.
Some pedons have an AB or a BA horizon; and some pedons have a Btg horizon formed in slackwater sediments.
The next part of the series control section (2B horizon that formed in loamy alluvium) has hue of 10YR, 2.5Y, 5Y, or is neutral; value of 4 to 6; and chroma of 0 to 2. Redoximorphic masses of iron accumulation typically have redder hue or higher chroma than the matrix. Some subhorizons contain low-chroma clay films or pressure faces. The 2B horizon typically is stratified, and is silt loam, loam, sandy loam, fine sandy loam, or very fine sandy loam, and averages 15 to 25 percent clay. The 2B horizon is calcareous and commonly contains shells of mollusks. Reaction is slightly alkaline or moderately alkaline.
The lower part of the series control section (2C) has hue of 10YR, 2.5Y, or 5Y; value of 4 to 6; and chroma of 1 to 3. It typically is stratified. Individual strata range from silty clay loam to very fine sand. Clay content ranges from less than 5 percent to about 30 percent and sand content ranges from about 10 to 95 percent. The 2C horizon typically is calcareous and reaction is neutral to moderately alkaline.
COMPETING SERIES: There are no competing series.
GEOGRAPHIC SETTING: McFain soils are in depressions which were formerly shallow lakes on flood plains of major rivers. Slope ranges from 0 to 2 percent. These soils formed in slackwater sediments and the underlying calcareous, stratified loamy or sandy alluvium that commonly contains shells of mollusks. These soils typically are subject to frequent flooding, but some areas are occasional or rare because of levees, locks and dams, or other flood-control structures. Mean annual temperature is 54 to 57 degrees F., mean annual precipitation is 36 to 44 inches, frost-free period is 170 to 210 days, and elevation is 340 to 450 feet above mean sea level.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Ambraw, Beaucoup, Darwin, Fults, Gorham, Landes, and Titus soils. The poorly drained Ambraw and Gorham soils contain less clay in the upper part of the series control section and occur on similar landform positions nearby. The poorly drained Darwin soils formed entirely in slackwater sediments and are on lower and less undulating parts of the flood plain nearby. The well drained Landes soils contain more sand and less clay in the upper part of the solum and are on higher parts of the flood plains nearby. The poorly drained Titus soils are on slightly higher parts of the undulating flood plain.
DRAINAGE AND PERMEABILITY: Very poorly and poorly drained. The potential for surface water runoff is low or negligible. Permeability is very slow in the upper slackwater sediments and moderate or moderately rapid in the loamy or sandy alluvium in the lower part of the solum and the substratum. In drained areas, depth to an intermittent apparent high water table is 0.5 foot above the surface to 1 foot below from November to May in most years. An undrained phase is recognized.
USE AND VEGETATION: Most areas are cropped. Soybeans are the principal crop. Corn or wheat are grown in some areas. Areas too wet for cultivation are in sedgges, rushes, and woody plants. Native vegetation is mixed prairie grasses, sedges, and hardwood trees.
DISTRIBUTION AND EXTENT: Southwestern and west-central Illinois and possibly eastern Missouri along major rivers; extent is small, and mainly in MLRA(s) 115B and 115C.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Indianapolis, Indiana
SERIES ESTABLISHED: Jersey County, Illinois, 1957.
REMARKS: The typical pedon was sampled and described from the same map unit as the previous typical pedon for this revision.
Diagnostic horizons and features in this pedon include:
Mollic epipedon - from the surface of the soil to a depth of 15 inches (Ap and A horizons). Cambic horizon - from a depth of 15 to 66 inches (2Btg, 2Btkg1, 2Btkg2, and 2BCtg horizons). Aquic conditions - endosaturation and reduction indicated by redoximorphic features (2Btg, 2Btkg1, 2Btkg2, 2BCtg and 2Cg horizons).
ADDITIONAL DATA: Lab data for several supporting pedons are on file at the USDA/NRCS state office in Champaign, Illinois.