LOCATION TOPEMAN WY+MTEstablished Series
TAXONOMIC CLASS: Fine, smectitic, nonacid, mesic Ustic Torriorthents
TYPICAL PEDON: Topeman silty clay loam-on a nearly level bedrock-controlled alluvial fan under sparse native vegetation. (The profile was dry to 48 inches when described. Colors are for dry soil unless otherwise stated. Low chromas are shale related.)
A--0 to 1 inch; light brownish gray (10YR 6/2) silty clay loam, dark grayish brown (10YR 4/2) moist; hard dispersed crust; hard, firm, sticky and plastic; few fine roots; slightly acid; clear smooth boundary. (one-half to one inch thick)
Bw--1 to 5 inches; gray (10YR 6/1) silty clay, dark gray (10YR 4/1) moist; weak coarse subangular blocky structure parting to weak medium granular; hard, firm, very sticky and plastic; few fine roots; medium acid; clear smooth boundary. (3 to 6 inches thick)
C1--5 to 19 inches; grayish brown (10YR 5/2) clay, dark grayish brown (10YR 4/2) moist; 30 percent weak coarse subangular blocky structure and 70 percent rock structure; extremely hard, very firm, very sticky and very plastic; few fine roots; few fine soft masses of calcium sulfate; 10 percent 1/4- to 3/8-inch soft shale platelets; medium acid; gradual wavy boundary. (10 to 20 inches thick)
C2--19 to 28 inches; light olive brown (2.5Y 5/4) clay; many light olive brown 2.5Y 5/6) mottles, dark grayish brown (2.5Y 4/2) moist; massive; extremely hard, very firm, very sticky and very plastic; common fine and medium threads of calcium sulfate; 25 percent 1/4- to 3/8-inch soft shale platelets; medium acid; clear smooth boundary. (5 to 12 inches thick)
C3--28 to 48 inches; grayish brown (2.5Y 5/2) clay; few light olive brown (2.5Y 5/6) mottles, dark gray (10YR 4/1) moist; massive; extremely hard, very firm, very sticky and very plastic; common fine threads of calcium sulfate; 30 percent soft 1/4- to 3/8-inch shale platelets; medium acid; gradual wavy boundary.
Cr--48 inches; brown, very strongly acid (pH 4.8) shale, containing yellowish brown mottles and many sulfate crystals.
TYPE LOCATION: Crook County, Wyoming; NE1/4 SE1/4 of sec. 19, T. 56 N., R 60 W.
RANGE IN CHARACTERISTICS: Depth to bedrock ranges from 40 to 60 inches. Shale platelets range from 10 to 35 percent in the control section and are soft, breaking down upon pretreatment. The control section is silty clay or clay and has 45 to 60 percent clay. Salinity usually ranges from 2 to 8 mmhos but in some wet areas ranges up to 16 mmhos.
The A horizon has hue of 10YR or 2.5Y, value of 5 through 7 dry, 3 or 4 moist, and chroma of 1 or 2. It is silty clay, clay, or silty clay loam. This horizon is acid or slightly acid.
The C horizon has hue of 10YR through 5, value of 4 through 6 dry, 3 or 4 moist, and chroma of 1 through 4. The upper part of the C horizon is clay and the lower part is clay or silty clay. Threads and seams of calcium sulfate range from few to many and are inherent to the parent sediments. Local movement does occur in pedons in some horizons.
COMPETING SERIES: These are the Rhoame series in the same family and the Bone and Graner series. Rhoame soils have friable A horizons in the series control section. Bone soils are very strongly alkaline in the C horizon. Graner soils contain more than 50 percent shale chips in the C horizon and are strongly acid or extremely acid.
GEOGRAPHIC SETTING: Topeman soils occupy small depressions or slickspots on bedrock-controlled alluvial fan aprons and toeslopes. Elevations are 3,200 to 5,600 feet. Slope gradients are 0 to 3 percent. The mean annual temperature ranges from 44 to 52 degrees F., and the annual precipitation is 12 to 16 inches.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Broadhurst, Demar, Maggin, and Querc soils and the competing Graner soils. Broadhurst soils are very fine textured and have vertic characteristics. Demar and Querc soils have an argillic horizon. Maggin soils are friable and do not have a horizon with calcium sulfate accumulation. None of the associated soils has a nearly barren, dispersed surface.
DRAINAGE AND PERMEABILITY: Moderately well drained; slow runoff; very slow permeability.
USE AND VEGETATION: Most areas are used primarily for grazing. These soils are usually barren, but, where present, native vegetation is sparse and consists of western wheatgrass, Gardner saltbush, and forbs.
DISTRIBUTION AND EXTENT: Western South Dakota and eastern Wyoming. The Topeman soils are moderately extensive in their collective areas but locally they are inextensive.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Denver, Colorado
SERIES ESTABLISHED: Crook County, Wyoming: 1978.