LOCATION UNION MOEstablished Series
TAXONOMIC CLASS: Fine, mixed, active, mesic Oxyaquic Fragiudalfs
TYPICAL PEDON: Union silt loam - on a 4 percent convex west facing slope in a pasture at an elevation of 885 feet. (Colors are for moist soil unless otherwise stated.)
Ap--0 to 8 inches; brown (10YR 4/3) silt loam; pale brown (10YR 6/3) dry; weak fine granular structure; very friable; few fine and common very fine roots; neutral; clear smooth boundary. (2 to 8 inches thick)
BE--8 to 11 inches; yellowish brown (10YR 5/4) silt loam; moderate fine granular structure; friable; common very fine roots; neutral; clear smooth boundary. (0 to 6 inches thick)
Bt1--11 to 17 inches; strong brown (7.5YR 4/6) silty clay loam; moderate fine subangular blocky structure; firm; common very fine roots; common distinct clay films on faces of peds; slightly acid; gradual smooth boundary.
Bt2--17 to 22 inches; dark yellowish brown (10YR 4/4) silty clay; moderate fine subangular blocky structure; firm; common very fine roots; many prominent clay films and common distinct silt coats on faces of peds; common fine distinct brown (7.5YR 4/4) masses of iron accumulation; very strongly acid; clear smooth boundary.
Bt3--22 to 28 inches; dark yellowish brown (10YR 4/4) silty clay; moderate fine subangular blocky structure; firm; few very fine roots; common prominent clay films on faces of peds; many fine distinct grayish brown (10YR 5/2) iron depletions; very strongly acid; gradual smooth boundary. (Combined thickness of the Bt horizon is 12 to 26 inches.)
2Btx1--28 to 37 inches; dark yellowish brown (10YR 4/4) silt loam matrix with grayish brown (10YR 5/2) vertical streaks (faces of polygonal) about 1/2 inch wide at 8 inch interval; few prominent clay fils within vertical streaks; weak very coarse prismatic structure with dense massive interiors; very firm; brittle; few very fine roots in vertical streaks; few fine discontinuous random vesicular pores within peds; few prominent clay films on faces of peds; 5 percent chert gravel; very strongly acid; gradual wavy boundary.
2Btx2--37 to 50 inches; brown (10YR 5/3) and light brownish gray (10YR 6/2) extremely gravelly silt loam; weak very coarse prismatic structure with dense massive interiors; very firm; brittle; few fine discontinuous random vesicular pores within peds; few distinct clay films on faces of peds; 75 percent chert gravel and 5 percent chert cobbles; very strongly acid; gradual wavy boundary. (Combined thickess of the 2Btx horizon is 9 to 42 inches.)
3Bt--50 to 60 inches; brown (7.5YR 5/4) and red (2.5YR 4/8) clay; weak very fine subangular blocky structure; firm; common distinct clay films on faces of peds; 40 percent chert gravel; moderately acid.
TYPE LOCATION: Gasconade County, Missouri; 1,300 feet west and 750 feet north of the southeast corner of sec. 31, T. 43 N., R. 4W; USGS Rosebud, Missouri quadrangle, latitude 38 degrees 25 minutes 21.5 seconds N. and longitude 91 degrees 24 minutes 37 seconds W.; UTM zone 15, 638,773 m. easting and 4,253,905 m. northing, NAD 83.
RANGE IN CHARACTERISTICS: The thickness of the solum ranges from 40 to more than 60 inches. Depth to the fragipan ranges from 18 to 36 inches. Depth to bedrock is more than 60 inches.
The A or Ap horizon has hue of 10YR, value of 3 to 5, and chroma of 2 or 3. Reaction is strongly acid to neural.
The E or BE horizon has hue of 10YR, value of 4 to 6, and chroma of 2 to 4. Reaction ranges from very strongly acid to neutral.
The Bt horizon has hue of 7.5YR or 5YR, rarely 10YR, value of 4 to 6, and chroma of 3 to 6. Some pedons have a matrix chroma of 2 in the layer immediately above the fragipan. The average clay content ranges from 35 to 42 percent, but individual horizons may exceed 42 percent. Chert gravel commonly is lacking but ranges up to 15 percent in the horizon immediately above the fragipan. Reaction ranges from slightly acid to very strongly acid.
The 2Btx horizon has hue of 10YR or 7.5YR, value of 4 to 6, and chroma of 1 to 6. It is silt loam, loam, silty clay loam or their gravelly or cobbly to extremely gravelly or extremely cobbly analogues. Rock fragment content ranges from 0 to 65 percent with individual bands ranging to 80 percent. Reaction is extremely acid to strongly acid.
The 3Bt or 4Bt horizon has hue of 7.5YR to 2.5YR, value of 3 to 6, and chroma of 4 to 8. It is silty clay loam, silty clay, clay or their gravelly to extremely gravelly analogues. Gravel content ranges from 0 to 70 percent. Reaction ranges from very strongly acid to slightly acid.
COMPETING SERIES: This is the Creldon series. Creldon soils have mollic colors in the A horizon.
GEOGRAPHIC SETTING: The Union soils occupy gently to moderately steep upland positions with slopes of 2 to 25 percent. They formed in 26 to 36 inches of loess underlain by clayey residuum weathered from cherty limestone or cherty dolomite. In some pedons, the clayey residuum is partially derived from components of sandstone, acid shale or unconsolidated Pennsylvanian deposits. The contact of the contrasting material is marked by a cherty old erosional surface in which the fragipan has developed. The fragipan is underlain by clayey cherty residuum or sediments. The mean annual precipitation ranges from 35 to 48 inches, and the mean annual temperature ranges from 54 degrees to 57 degrees F.
GEOGRAPHICALLY ASSOCIATED SOILS: These include the Beemont, Clarksville, Goss, and Lebanon soils. Beemont soils occur on steeper lower slopes and do not have a fragipan. Clarksville and Goss soils contain more than 35 percent coarse fragments in the particle size control section, do not have a fragipan, and occupy lower positions on the landscape. Lebanon soils are ultisols.
DRAINAGE AND PERMEABILITY: Moderately well drained. The surface runoff index is high to very high. Permeability is moderate above the fragipan and slow in the fragipan. The saturated hydraulic conductivity is low.
USE AND VEGETATION: Most areas are in pasture or forest. A small acreage is cropped to corn, small grains, and hay. Native vegetation is hardwood forest.
DISTRIBUTION AND EXTENT: The Ozark Highlands area (MLRA 116A) of southern Missouri. Union soils are extensive, about 400,000 acres have been mapped to date.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Morgantown, West Virginia
SERIES ESTABLISHED: Franklin County, Missouri, 1909.
REMARKS: Diagnostic horizons and features recognized in the series are: ochric epipedon - the zone from the surface of the soil to a depth of 8 inches (Ap horizon);
argillic horizon - the zone from approximately 11 inches to 28 inches (Bt1, Bt2 and Bt3 horizons);
fragipan - the zone from approximately 28 inches to 50 inches (2Btx1 and 2Btx2 horizons); lower argillic horizon (3Bt horizon) 50 to 60 inches; udic soil moisture regime.
Oxyaquic feature - a zone of saturation perched immediately above the fragipan.
ADDITIONAL DATA: The representative pedon location has been moved from Moniteau County, Missouri to Gasconade County, Missouri.
University of Missouri Soil Characterization Laboratory Data reference number M9107301.
NASIS pedon number 99MO073023