LOCATION POWELLBUTTE ORTentative Series
TAXONOMIC CLASS: Fine-loamy, mixed, superactive, frigid Vitrandic Argixerolls
TYPICAL PEDON: Powellbutte gravelly ashy loam, on a north facing 15 percent slope, rangeland. (Colors are for moist soils unless otherwise noted.)
A--0 to 5 inches; very dark brown (10YR 2/2) gravelly ashy loam, dark grayish brown (10YR 4/2) dry; weak fine granular structure; soft, very friable, nonsticky and nonplastic; many very fine and fine roots; many fine vesicular pores; 15 percent gravel and 10 percent cobbles; neutral (pH 6.7); clear smooth boundary. ( 3 to 6 inches thick )
AB--5 to 11 inches; very dark brown (10YR 2/2) gravelly ashy loam, dark grayish brown (10YR 4/2) dry; weak fine and medium subangular blocky structure; soft, very friable, slightly sticky and slightly plastic; many very fine and fine and few medium roots; many fine and very fine tubular pores; 15 percent gravel; neutral (pH 6.8); clear smooth boundary. ( 4 to 8 inches thick )
2Bt1--11 to 19 inches; very dark grayish brown (10YR 3/2) gravelly clay loam, grayish brown (10YR 5/2) dry; moderate fine and medium subangular blocky structure; hard, firm, slightly sticky and slightly plastic; common fine roots and few medium roots; common fine tubular pores; common faint clay films on faces of peds and lining pores; 15 percent gravel; neutral (pH 7.0); clear smooth boundary. ( 5 to 12 inches thick )
2Bt2--19 to 25 inches; very dark grayish brown (10YR 3/2) gravelly clay, grayish brown (10YR 5/2) dry; strong fine and medium subangular blocky structure; very hard, very firm, moderately sticky and moderately plastic; few fine, medium, and coarse roots; few fine tubular pores; common distinct clay films on faces of peds and lining pores; 25 percent gravel; neutral (pH 7.2); abrupt smooth boundary. ( 7 to 15 inches thick )
2Crt--25 to 28 inches; weathered basalt with clay accumulations in fractures.
2R--28 inches; basalt.
TYPE LOCATION: Crook County, Oregon; located 100 feet south and 1500 feet west of the NE corner of section 23, T. 16 S, R. 16 E.
RANGE IN CHARACTERISTICS: These soils are usually moist but are dry in the moisture control section for 70 to 90 days following the summer solstice. The mean annual soil temperature is 42 to 47 degrees F. The A and AB horizons have a phosphate retention of 15 to 25 percent, acid oxalate aluminum plus one-half the iron of 0.4 to 0.8 percent and 15 to 30 percent glass. Depth to the 2Bt horizon is 7 to 14 inches. Depth to bedrock is 20 to 40 inches. The mollic epipedon is 20 to 30 inches thick. The particle-size control section averages 30 to 35 percent clay.
The A horizon has value of 2 or 3 moist, 3 or 4 dry, and chroma of 1 or 2 moist and dry. It contains 10 to 40 percent gravel, 0 to 10 percent cobbles, and 0 to 10 percent stones.
The AB horizon has value of 2 or 3 moist, 3 through 5 dry, and chroma of 1 or 2 moist and dry. It is ashy loam or ashy clay loam and contains 10 to 20 percent gravel and 20 to 30 percent clay.
The 2Bt horizon has value of 2 or 3 moist, 4 or 5 dry, and chroma of 2 through 4 moist and dry. It is clay loam or clay and contains 5 to 35 percent gravel and 27 to 45 percent clay. Clay texture occurs in the horizon immediately above the bedrock.
COMPETING SERIES: These are the Melhorn, Said, and Salcreek series. Melhorn and Salcreek soils are very deep to bedrock. Said soils are deep to bedrock.
GEOGRAPHIC SETTING: Powellbutte soils are on hillsopes and plateaus at elevations of 3,000 to 4,500 feet. Slopes range from 0 to 30 percent. The soils formed in residuum and colluvium derived from basalt and tuff with an influence of volcanic ash in the surface. The climate is characterized by cold wet winters and hot dry summers. The mean annual precipitation is 12 to 14 inches, the mean annual temperature is 40 to 46 degrees F, and the frost-free period is 50 to 80 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Anatone, Bocker, Cadlebutte, Lickskillet, Searles, Skullhollow, and Teguro soils. Anatone soils are loamy-skeletal, shallow, and are on adjacent ridgetops of mesas. Bocker soils are loamy-skeletal, very shallow, and are on adjacent ridgetops of mesas. Cadlebutte soils are fine and are on adjacent backslopes of mesas. Lickskillet soils are loamy-skeletal, shallow and are on adjacent south-facing sideslopes. Searles soils are loamy-skeletal and are on adjacent south-facing sideslopes. Skullhollow soils are loamy-skeletal. Teguro soils are shallow and are on adjacent backslopes of mesas.
DRAINAGE AND PERMEABILITY: Well drained, permeability is moderately slow.
USE AND VEGETATION: Powellbutte soils are used mainly for livestock grazing and wildlife habitat. The native vegetation is Idaho fescue, bluebunch wheatgrass, mountain big sagebrush, and western juniper.
DISTRIBUTION AND EXTENT: Central Oregon; MLRA 10, John Day area. This series is not extensive.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Portland, Oregon
SERIES PROPOSED: Crook County Area, Oregon; 1999.
REMARKS: Diagnostic horizons and features in this pedon include:
Mollic epipedon (Pachic) - the zone from the surface to a depth of 25 inches (A, AB, 2Bt1 and 2Bt2 horizons)
Argillic horizon - from a depth of 11 to 25 inches (2Bt horizon)
Vitrandic feature - from the surface to a depth of 11 inches (A and AB horizons)