LOCATION SNOMO SD+WYEstablished Series
TAXONOMIC CLASS: Very-fine, smectitic, mesic Torrertic Dystrustepts
TYPICAL PEDON: Snomo clay - on a 8 percent north-facing slope in scattered trees with native grass understory. (Colors are for dry soil unless otherwise stated.)
A1--0 to 2 inches; light gray (10YR 6/1) silty clay, very dark grayish brown (10YR 3/2) moist; weak thick platy structure parting to weak fine granular; hard, friable, slightly sticky and slightly plastic; many fine and medium roots; slightly acid; clear smooth boundary.
A2--2 to 5 inches; light gray (10YR 6/1) clay, very dark grayish brown (10YR 3/2) moist; weak fine subangular blocky structure; hard, friable, sticky and plastic; common fine roots; moderately acid; clear smooth boundary. (Combined A horizons 4 to 8 inches thick)
Bw1--5 to 14 inches; light brownish gray (10YR 6/2) clay, very dark grayish brown (10YR 3/2) moist, rubbed dark grayish brown (10YR 4/2) moist; weak coarse prismatic structure parting to weak medium and fine subangular blocky; very hard, friable, sticky and plastic; common fine roots; strongly acid; clear smooth boundary.
Bw2--14 to 28 inches; pale brown (10YR 6/3) clay, dark brown (10YR 3/3) moist, rubbed brown (10YR 4/3) moist; weak coarse prismatic structure parting to weak medium subangular blocky; hard, friable, sticky and plastic; few fine roots; few fine fragments of shale; very strongly acid; clear wavy boundary. (Combined Bw horizons 20 to 35 inches thick)
BC--28 to 38 inches; pale brown (10YR 6/3) clay, dark grayish brown (10YR 4/2) moist; common fine and medium distinct mottles of yellowish brown (10YR 5/6) and strong brown (75.YR 5/6); weak coarse subangular blocky structure; hard, friable, sticky and plastic; few fine roots; many fine fragments of shale; extremely acid; gradual smooth boundary. (0 to 15 inches thick)
C1--38 to 45 inches; pale brown (10YR 6/3) clay, brown (10YR 4/3) moist; few fine distinct mottles of yellow (2.5Y 8/6) massive; slightly hard, friable, sticky and plastic; few fine roots; many fine fragments of shale, extremely acid; abrupt wavy boundary.
C2--45 to 50 inches; very pale brown (2.5Y 7/3) and yellow (5Y 8/6) clay, light olive brown (2.5Y 5/3) and yellow (5Y 7/6) moist; massive; slightly hard, friable, sticky and plastic; many coarse fragments of brittle shale; extremely acid; clear wavy boundary.
Cr--50 to 60 inches; gray (10YR 5/1) acid shale, black (N 2/) moist; yellow (5Y 8/6) and yellowish red (5YR 5/8) coatings on fracture faces of shale.
TYPE LOCATION: Butte County, South Dakota; 8 miles east and 2 miles south of Belle Fourche; 2440 feet north and 115 feet east of the southwest corner of sec. 19, T. 8 N., R. 4 E.
RANGE IN CHARACTERISTICS: Bedded shale typically is between a depth of 40 and 60 inches but is below 60 inches in some pedons. Colors throughout the soil are inherent to the shale.
The A horizon has hue of 10YR, value of 5 to 7 and 3 or 4 moist, and chroma of 1 or 2. It is silty clay or clay and contains 0 to 15 percent by volume of fine fragments of shale less than 3 mm in size. It is extremely acid to slightly acid. Some pedons have a thin distinct E horizon as evidenced by prominent clean silt and sand grains.
The Bw horizon has hue of 10YR, 2.5Y, and 7.5YR, value of 5 or 6 and 3 or 4 moist, and chroma of 2 to 4. Moist value typically is one unit higher when rubbed. It has 0 to 20 percent by volume of fine fragments of shale less than 3 mm in size. It is strongly acid to extremely acid.
The BC and C horizons have hue of 10YR or 2.5Y, value of 5 or 6 and 3 to 5 moist, and chroma of 1 to 3. Moist value typically is one unit higher when rubbed. They have 15 to 50 percent by volume of fine to coarse fragments of shale ranging from 1 to 25 mm in size. They are very strongly acid or extremely acid.
The Cr horizon is multicolored in hue of 10YR, 2.5Y, or 5Y; and is very hard and brittle but has a hardness of less than 3 on the Moh's scale of hardness. It is very strongly acid or extremely acid.
COMPETING SERIES: There are no other series in the same family.
GEOGRAPHIC SETTING: Snomo soils are on gently sloping to moderately steep uplands. Slope gradients range from 2 to 20 percent. The soil formed in clayey materials weathered from acid shale. Mean annual temperature ranges from 43 to 48 degrees F, and precipitation from 14 to 18 inches.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Graner and Grummit soils. Graner soils are on similar positions as the Snomo soil. They do not have a cambic horizon. Grummit soils are on adjacent steeper slopes and have bedded shale within depths of 20 inches.
DRAINAGE AND PERMEABILITY: Well drained. Surface runoff is very low to medium depending on slope. Permeability is moderate.
USE AND VEGETATION: These soils are used primarily as native rangeland. Principal native vegetation includes sunsedge, western wheatgrass, prairie leadplant, little bluestem, big bluestem, bur oak, and ponderosa pine.
DISTRIBUTION AND EXTENT: Western South Dakota. The series is of moderate extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Denver, Colorado
SERIES ESTABLISHED: Butte County, South Dakota, 1970.
REMARKS: Diagnostic horizons and features recognized in this pedon are: ochric epipedon - the zone from the surface of the soil to a depth of about 5 inches (A1 and A2 horizons); cambic horizon - the zone from a depth of about 5 to 28 inches (Bw1 and Bw2 horizons).
ADDITIONAL DATA: Lincoln lab data nos. 70L428-70L435 is available.