LOCATION COATSBURG ILEstablished Series
TAXONOMIC CLASS: Fine, smectitic, mesic Vertic Argiaquolls
TYPICAL PEDON: Coatsburg silt loam, on a north-facing 10 percent slope in a cultivated field at an elevation of 213 m (700 feet). (Colors are for moist soil unless otherwise stated.)
Ap--0 to 15 cm (0 to 6 inches); very dark gray (10YR 3/1) silt loam, dark grayish brown (10YR 4/2) dry; moderate fine granular structure; friable; many fine and medium roots; moderately acid; abrupt smooth boundary.
AB--15 to 25 cm (6 to 10 inches); very dark gray (10YR 3/1) silty clay loam, gray (10YR 5/1) dry; weak medium subangular blocky structure parting to moderate fine subangular blocky; firm; common fine roots; few prominent light gray (10YR 7/1) dry, silt coatings on faces of peds; common fine prominent irregular strong brown (7.5YR 5/6) masses of iron oxide throughout; many fine prominent irregular light olive brown (2.5Y 5/4) masses of iron oxide throughout; moderately acid; clear wavy boundary. [Combined thickness of the A horizon is 25 to 51 cm (10 to 20 inches)]
2Btg1--25 to 36 cm (10 to 14 inches); dark grayish brown (10YR 4/2) silty clay loam; weak medium subangular blocky structure; firm; few fine roots; common distinct very dark gray (10YR 3/1) organo-clay films on faces of peds; common distinct dark gray (10YR 4/1) clay films on faces of peds; common fine prominent irregular strong brown (7.5YR 5/6) and many fine prominent irregular light olive brown (2.5Y 5/4) masses of iron oxide throughout; moderately acid; clear wavy boundary.
2Btg2--36 to 48 cm (14 to 19 inches); grayish brown (10YR 5/2) silty clay; weak coarse prismatic structure parting to weak medium subangular blocky; firm; few fine and medium roots; common distinct very dark gray (10YR 3/1) organo-clay films on faces of peds; many fine prominent irregular strong brown (7.5YR 5/6) masses of iron oxide throughout; common fine faint irregular light brownish gray (10YR 6/2) iron depletions throughout; moderately acid; clear wavy boundary.
2Btg3--48 to 66 cm (19 to 26 inches); grayish brown (10YR 5/2) silty clay loam; weak very coarse prismatic structure; firm; few fine roots; few distinct very dark gray (10YR 3/1) organo-clay films on faces of peds; common distinct gray (10YR 5/1) clay films on faces of peds; common fine and medium prominent irregular strong brown (7.5YR 5/6) masses of iron oxide throughout; many fine faint irregular light brownish gray (10YR 6/2) iron depletions throughout; moderately acid; clear wavy boundary.
2Btg4--66 to 97 cm (26 to 38 inches); grayish brown (10YR 5/2) silty clay loam; weak very coarse prismatic structure; firm; few very fine roots; few distinct gray (10YR 5/1) clay films on faces of peds and in pores; common fine and medium prominent irregular black (2.5Y 2.5/1) masses of iron and manganese oxide throughout; common fine and medium prominent irregular strong brown (7.5YR 5/6) masses of iron oxide throughout; many fine and medium faint irregular light brownish gray 10YR 6/2) iron depletions throughout; moderately acid; clear wavy boundary.
2Btg5--97 to 114 cm (38 to 45 inches); light brownish gray (10YR 6/2) silty clay loam; moderate very coarse prismatic structure; firm; few distinct dark gray (10YR 4/1) clay films lining root channels and pores; common distinct grayish brown (10YR 5/2) clay films on faces of peds; common prominent light gray (10YR 7/2) silt coatings on faces of peds; common medium prominent irregular brownish yellow (10YR 6/8) masses of iron oxide throughout; slightly acid; clear wavy boundary.
2Btg6--114 to 157 cm (45 to 62 inches); gray (10YR 6/1) silty clay loam; moderate very coarse prismatic structure; firm; many prominent light gray (10YR 7/2) silt coatings on faces of peds; common distinct gray (10YR 5/1) clay films on faces of peds; few medium prominent irregular black (2.5Y 2.5/1) masses of iron and manganese oxide throughout; common medium and coarse prominent irregular brownish yellow (10YR 6/6) masses of iron oxide throughout; slightly acid; clear wavy boundary.
2Btg7--157 to 178 cm (62 to 70 inches); light brownish gray (10YR 6/2) silty clay; weak very coarse prismatic structure parting to moderate medium subangular blocky; very firm; few distinct gray (10YR 6/1) clay films on faces of peds and in pores; common fine prominent irregular black (2.5Y 2.5/1) masses of iron and manganese oxide throughout; many medium prominent irregular strong brown (7.5YR 5/6) masses of iron oxide throughout; 2 percent pressure faces throughout; slightly acid; gradual wavy boundary. [Combined thickness of the 2Bt horizon is 76 to 178 cm (30 to 70 inches)]
2BCg--178 to 203 cm (70 to 80 inches); gray (10YR 6/1) silty clay; weak very coarse prismatic structure; firm; common fine prominent irregular black (2.5Y 2.5/1) masses of iron and manganese oxide throughout; many coarse prominent irregular brownish yellow (10YR 6/6) masses of iron oxide throughout; slightly acid.
TYPE LOCATION: Adams County, Illinois; about 1/2 mile southeast of La Prairie; 2,550 feet east and 2,400 feet north of the southwest corner of sec. 20, T. 2 N., R. 5 W.; USGS Augusta, IL. topographic quadrangle; latitude 40 degrees 8 minutes 33 seconds N, and longitude 90 degrees 59 minutes 58 seconds W. NAD 27.
RANGE IN CHARACTERISTICS: The depth to the base of the argillic horizon ranges 127 to 203 cm (50 to 80 inches). The thickness of the mollic epipedon ranges from 25 to 51 cm (10 to 20 inches). The dominant clay mineral in the Bt horizon is smectite, but the content of illite increases with increasing depth. The particle-size control section averages between 35 and 45 percent clay and from 15 to 35 percent fine sand or coarser material. Free carbonates are present in some pedons below a depth of 152 cm (60 inches).
The Ap, A, or AB horizon has a hue of 10YR, value of 2 or 3 (4 or 5 dry), and chroma of 1 or 2 moist or dry. It commonly is silt loam, but silty clay loam and clay loam are within the range, particularly in eroded pedons. It average 20 to 35 percent clay and 5 to 15 percent sand. Reaction ranges from strongly acid to slightly alkaline, the latter in pedons that have been limed.
Some pedons have a thin Btg horizon formed in loess above the 2Btg horizon formed in till.
The Btg or 2Btg horizon is neutral or has hue of 10YR, 2.5Y, or 5Y, value of 3 to 6, and chroma of 0 to 2. Redoximorphic features have hues of 5Y, 2.5Y, 10YR, 7.5YR, or 5YR, value of 3 to 6, and chroma of 1 to 8. Texture is clay, clay loam, silty clay, or silty clay loam. It averages 35 to 45 percent clay and 15 to 35 percent sand. Reaction is strongly acid or moderately acid in at least one subhorizon, and ranges from strongly acid to slightly acid. (See remarks.)
The 2BCg, 2BC, 2C or 2Cg horizon, where present, is neutral or has hue of 10YR, 7.5YR, 2.5Y, 5Y, value of 4 to 6, and chroma of 0 to 8. It is clay, clay loam, silty clay, silty clay loam, or loam. It averages 20 to 45 percent clay. Reaction ranges from moderately acid to slightly alkaline.
COMPETING SERIES: These are the Butler, Carbika, Chancellor, Clarinda, Edinburg, Fosterburg, Haig, Lodgepole, Mazaska, Minnetonka, Sacville, Sampsel, Taintor, Terrabella, Virden, and Worthing series. Butler and Clarinda soils average more than 45 percent clay in the particle-size control section. Carbika and Sacville soils have a mean annual soil temperature of more than 13 degrees C (56 degrees F). Chancellor, Lodgepole and Worthing soils have mollic epipedons that extend to depths greater than 51 cm (20 inches). Edinburg, Fosterburg, Haig, Minnetonka, Taintor, and Virden soils average less than 15 percent sand in the particle-size control section. In addition, Fosterburg soils contain a concentration of between 5 and 15 percent exchangeable sodium. Mazaska soils have free carbonates above a depth of 152 cm (60 inches). Sampsel soils have a paralithic contact within a depth of 203 cm (80 inches). Terrabella soils have matrix colors with hues redder than 10YR in the middle part of the series control section.
GEOGRAPHIC SETTING: Coatsburg soils are on the upper ends of incised drainageways and convex side slopes on till plains. They formed in 51 cm (20 inches) or less of loess or other silty material, and glacial till or accretion gley that contains a strongly developed paleosol. Slopes commonly are 5 to 10 percent, but range from 4 to 20 percent. Mean annual temperature ranges from 8 to 12 degrees C (46 to 54 degrees F); mean annual soil temperature ranges from 11 to 13 degrees C (52 to 56 degrees F); mean annual precipitation ranges from 740 to 1020 mm (29 to 40 inches); frost free days range from 150 to 190 days; and elevation ranges from 122 to 305 m (400 to 1000 feet) above sea level.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Assumption, Atlas, Keller, and Ogle soils. The well drained or moderately well drained Assumption soils are upslope or at higher elevations than Coatsburg soils. The somewhat poorly drained Atlas and Keller soils, and the well drained Ogle soils are on similar slopes nearby. Atlas soils are the forested member of a biosequence with Coatsburg soils.
DRAINAGE AND SATURATED HYDRAULIC CONDUCTIVITY: Coatsburg soils are poorly drained. Saturated hydraulic conductivity is 0.01 to 0.42 micrometers per sec (very slow permeability). Surface runoff potential is medium to very high. At undisturbed sites there is a perched water table at depths of 0 to 1.0 feet during the spring in most years. These soils are seasonally wet and seepy.
USE AND VEGETATION: Most areas are used for pasture or for forages that are cut for hay. Cultivated crops are on some of the less sloping areas. Native vegetation is prairie grasses.
DISTRIBUTION AND EXTENT: Western and northwestern Illinois; LRRs K and M, MLRAs 95B, 108B, and 115C. The series is of small extent.
MLRA OFFICE RESPONSIBLE: Indianapolis, Indiana
SERIES ESTABLISHED: Stephenson County, Illinois, 1969.
REMARKS: The variability of the properties in the Coatsburg series is related to the geologic truncation of the paleosol before it was buried by loess, and to the extent that modern soil forming processes have altered the paleosol. Many of the properties of the 2Btg horizon are believed to have been inherited from the paleosol. It is difficult to differentiate the properties of the lower part of the modern soil from those of the paleosol in many pedons. Some mapped areas of this soil contain buried horizons (subscript b) of the paleosol beneath the modern solum. Calcium and other bases have been replenished in some pedons after burial by loess by seepage water from upslope or from the mantling material. This causes the reaction of the solum to have a wide range. The type location was moved to this more representative pedon in 1996.
Diagnostic horizons and features recognized in this pedon are:
mollic epipedon - from a depth of 0 to 25 cm (0 to 10 inches) (Ap and AB horizons)
argillic horizon - from a depth 25 to 178 cm (10 to 70 inches) (2Btg horizons)
lithologic discontinuity at a depth of 25 cm (10 inches)