LOCATION DUNBARTON WI+IA IL MNEstablished Series
TAXONOMIC CLASS: Clayey, smectitic, mesic Lithic Hapludalfs
TYPICAL PEDON: Dunbarton silt loam, on a northwest-facing convex slope of 9 percent in a cultivated field at an elevation of about 1,000 feet. (Colors are for moist soil unless otherwise stated.)
Ap--0 to 7 inches; dark grayish brown (10YR 4/2) silt loam, pale brown (10YR 6/3) dry; weak and moderate medium granular structure; friable; common roots; neutral; abrupt smooth boundary. (6 to 8 inches thick)
BE--7 to 9 inches; brown (10YR 4/3) silt loam; moderate fine subangular blocky structure; firm; common roots; neutral; clear wavy boundary. (0 to 3 inches thick)
2Bt1--9 to 12 inches; brown (7.5YR 4/4) silty clay loam; moderate fine angular blocky structure; firm; few faint patchy clay films and a few very dark gray (10YR 3/1) stains on faces of peds; common roots; neutral; clear wavy boundary.
2Bt2--12 to 18 inches; reddish brown (5YR 4/4) clay; strong fine and medium angular blocky structure; very firm; common distinct clay films and a few very dark gray (10YR 3/1) stains on faces of peds; common roots; neutral; clear irregular boundary. (Combined thickness of the 2Bt horizons ranges from 4 to 9 inches.)
3R--18 to 60 inches; very pale brown (10YR 7/3) or white (10YR 8/1) dolostone with reddish brown (5YR 4/4) clay in joints extending down into the bedrock several feet.
TYPE LOCATION: Lafayette County, Wisconsin; about 4 miles southwest of Argyle; 2,690 feet east and 700 feet north of the SW corner of Sec. 31, T. 3 N., R. 5 E.
RANGE IN CHARACTERISTICS: Solum thickness ranges from 12 to 20 inches, which is the same as the depth to bedrock. The loess mantle generally is 8 to 10 inches thick but ranges from none, where the soil is eroded, to a maximum of about 15 inches. The solum typically is neutral but ranges from medium acid, in the upper part, to mildly alkaline in the lower part. Volume of angular pebbles and channers, mainly chert, dolostone, and limestone, ranges from 0 to 30 percent and volume of flagstones ranges from 0 to 20 percent in the pedisediment and residuum. The upper part of the solum formed in loess generally does not contain pebbles.
The Ap horizon has 10YR or 7.5YR hue, value of 3 through 5, and chroma of 2 through 4. It is typically silt loam, but severely eroded phases are silty clay loam. Where this soil is undisturbed, it has a silt loam A horizon 2 to 4 inches thick and a silt loam E horizon 2 to 5 inches thick. The A horizon has 10YR hue, value of 2 or 3, and chroma 1 or 2. The E horizon has 10YR hue value of 4 or 5, and chroma of 2 or 3. In most cultivated pedons, the E is mixed with the Ap horizon.
The BE horizon, or Bt horizon where present, has 7.5YR or 10YR hue, value of 4 or 5 and chroma of 3 or 4. It is silt loam or silty clay loam.
The 2Bt horizon has 10YR, 7.5YR, 5YR, or 2.5YR hue; value of 4 or 5, and chroma of 3 through 6. It typically is silty clay loam, clay loam, silty clay, or clay. The argillic horizon averages between 35 to 75 percent clay. The average is dependent upon the relative amounts of loess and residuum making up the argillic horizon.
The 3Bt horizon, where present, has hue of 7.5YR or 10YR, value of 3 or 4, and chroma of 1 to 4. It is sandy loam, clay loam, loam, or the rock fragment analogs.
In some places, the bedrock is solid, but in other places, it has joints filled with residuum or has a thin Cr layer over the bedrock. The joints extend downward for several feet. Typically the bedrock is dolomite, but some is other kinds of linestone.
COMPETING SERIES: This is the only series in this family. Other series in closely related families are Dubuque, Edmund, Lamoille, NewGlarus, Nordness, and Sogn. Dubuque and NewGlarus soils have less clay in the upper part of the Bt horizons, thicker sola, and have bedrock at depths between 20 to 40 inches. Edmund soils have mollic epipedons. Lamoille soils have a loamy-skeletal 3B horizon within a depth of 40 inches. Nordness soils are loamy and have somewhat thinner sola. Sogn soils have mollic epipedons and do not have argillic horizons.
GEOGRAPHIC SETTING: Dunbarton soils are on upland ridges and sideslopes with convex and plane slopes of 2 to 60 percent gradient. The soils formed in 8 to 10 inches of loess and the underlying clayey pedisediment and in residuum that contains variable amounts of chert or limestone (dolostone) fragments, or both. Bedrock is at a depth of less than 20 inches. Mean annual precipitation ranges from 26 to 37 inches, and mean annual temperature from 42 to 54 degrees F.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Dubuque and Sogn soils. The well drained Dubuque soils are above the Dunbarton soils on the broader ridgetops where the depth to bedrock is greater than 20 inches. The Sogn are nearby on drier sites.
DRAINAGE AND PERMEABILITY: Well drained. Runoff is medium to rapid. Permeability is moderately slow.
USE AND VEGETATION: The less sloping areas are cropped mainly to corn, small grain, and hay. Soybeans are also grown in some places. Steeper slopes are in woodland or used for pasture. Native vegetation was mainly oaks and hickories.
DISTRIBUTION AND EXTENT: Southwestern and western Wisconsin, northwestern Illinois, eastern Iowa, and possibly southeastern Minnesota. The soil is of moderate extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: St. Paul, Minnesota
SERIES ESTABLISHED: Lafeyette County, Wisconsin, 1965.
REMARKS: Dunbarton soils were at one time included in the Dubuque series as a thin phase.
Diagnostic horizons and features recognized in this pedon are: ochric epipedon - zone from surface of soil to depth of 7 inches (Ap); argillic horizon - zone from 9 to 18 inches (2Bt1, 2Bt2).