LOCATION THREETOP WYEstablished Series
TAXONOMIC CLASS: Fine-loamy, mixed, superactive, mesic Ustic Calciargids
TYPICAL PEDON: Threetop sandy loam--rangeland. (Colors are for dry soil unless otherwise stated.)
A--0 to 2 inches; brown (10YR 5/3) sandy loam, dark brown (10YR 3/3) moist; weak fine granular structure; soft, very friable, nonsticky and nonplastic; many fine roots; mildly alkaline (pH 7.4); clear wavy boundary. (1 to 3 inches thick)
Bt1--2 to 7 inches; brown (10YR 5/3) sandy clay loam, dark brown (10YR 4/3) moist; moderate medium prismatic structure parting to moderate medium subangular blocky; hard, friable, slightly sticky and slightly plastic; many fine roots; common distinct clay skins on faces of peds; 10 percent angular sandstone pebbles; mildly alkaline (pH 7.6); clear wavy boundary.
Bt2--7 to 13 inches; brown (10YR 5/3) sandy clay loam, dark brown (10YR 4/3) moist; moderate medium prismatic structure parting to moderate medium subangular blocky; hard, friable, slightly sticky and slightly plastic; many fine roots; common distinct clay skins on faces of peds; slight effervescence, calcium carbonate disseminated; 10 percent angular sandstone pebbles; moderately alkaline (pH 8.2); clear wavy boundary. (Combined thickness of the Bt horizon is 8 to 16 inches.)
Bk1--13 to 18 inches; pale brown (10YR 6/3) sandy clay loam, dark brown (10YR 4/3) moist; weak medium subangualr blocky structure; hard, friable, nonsticky and slightly plastic; common fine roots; violent effervescence, calcium carbonate disseminated; 10 percent angular sandstone pebbles; moderately alkaline (pH 8.4); gradual wavy boundary.
Bk2--18 to 24 inches; very pale brown (10YR 7/3) very gravelly sandy loam, pale brown (10YR 6/3) moist; massive; slightly hard, friable, nonsticky and nonplastic; violent effervescence, calcium carbonate disseminated and as thick coatings on undersides of pebbles; 45 percent angular sandstone pebbles; strongly alkaline (pH 8.6). (Combined thickness of Bk horizon is 10 to 27 inches.)
R--24 inches; hard, argillaceous sandstone.
TYPE LOCATION: Natrona County, Wyoming; about 12 miles NNW of the town of Powder River; 1,820 feet south and 2,200 feet east of the NW corner of sec. 8, T. 37 N., R. 85 W.
RANGE IN CHARACTERISTICS: Depth to lithic contact is 20 to 40 inches. Depth to the base of the argillic horizon is 10 to 18 inches. Rock fragments are mainly angular sandstone pebbles. Hue is 10YR or 7.5YR. The mean annual soil temperature is 47 to 51 degrees F.
The A horizon has value of 4 or 5 dry, 3 or 4 moist, and chroma of 2 through 4. It is slightly acid through mildly alkaline.
The Bt horizon has value of 5 or 6 dry, 4 or 5 moist, and chroma of 3 or 4. It is loam, sandy clay loam or clay loam with 25 to 35 percent clay and more than 35 percent fine sand or coarser. Rock fragments range from 0 to 15 percent. It is neutral through moderately alkaline.
The Bk horizon has value of 5 through 8 dry, 4 through 6 moist, and chroma of 3 or 4. It is sandy clay loam, sandy loam, or loam. Rock fragments range from 5 to 50 percent and commonly increase with depth. Calcium carbonate equivalent is 15 to 30 percent, most of which is authigenic. It is moderately alkaline or strongly alkaline.
The R is hard, argillaceous sandstone. It commonly is more than 5 feet thick.
COMPETING SERIES: These are the Balon, Barx, Bowbac, Buckle, Cambria, Cerrillos, Clovis, Cushman, Decolney(T), Fattig, Fernando, Flaco, Forkwood, Fort Collins, Gaddes, Gapbutte(T), Haggerman, Harbord, Hiland, Los Alamos, Maysdorf, Millett, Oelop, Olney, Palacid, Penistaja, Pokeman, Potts, Progresso, Pugsley, Rauzi, Scholle, Spangler, Spenlo, Stoneham, Sundance, Tapia, Toluca, Tuweep, and Yenlo series. Balon, Barx, Buckle, Cambria, Cerrillos, Clovis, Decolney, Fernando, Forkwood, Fort Collins, Harbord, Hiland, Los Alamos, Maysdorf, Millet, Oelop, Olney, Penistaja, Potts, Rauzi, Scholle, Spenlo, Stoneham, Sundance, Tapia, Toluca, Tuweep, and Yenlo soils are deep. Bowbac, Cushman, Gaddes and Pokeman soils have a paralithic contact. Fattig soils have dark lithachromic colors inherited from carbonaceous parent material. Flaco soils have less than 35 percent sand in the argillic horizon. Gapbutte soils have hues redder than 7.5YR. Hagerman soils do not have a calcic horizon and have warmer mean annual soil temperatures. Palacid and Progresso soils are usually dry in the moisture control section during the months of April, May and June. Pugsley and Spangler soils are noncalcareous throughout.
GEOGRAPHIC SETTING: Threetop soils are on dipslopes. They formed in slopewash alluvium and residuum derived dominantly from argillaceous sandstone. Slopes range from 3 to 12 percent. Elevation is 4000 to 6,700 feet. The mean annual precipitation is 10 to 14 inches, and the mean annual temperature is 42 to 50 degrees F. The frost-free season is 110 to 130 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Sunup and the competing Bowbac and Hiland soils. Sunup soils are shallow, loamy-skeletal and do not have an argillic horizon.
DRAINAGE AND PERMEABILITY: Well drained; medium or rapid runoff; moderate permeability.
USE AND VEGETATION: These soils are used mainly for livestock grazing and wildlife habitat. Native vegetation is mainly rhizomatous wheatgrass, needleandthread, and big sagebrush.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana
SERIES ESTABLISHED: Natrona County, Wyoming; 1985.
REMARKS: Diagnostic horizons and features recognized in this pedon are: 1. Ochric epipedon - 0 to 2 inches (A)
2. Argillic horizon - 2 to 13 inches (Bt1,Bt2)
3. Calcic horizon - 13 to 24 inches (Bk1,Bk2)
4. Lithic contact - 24 inches (R)