LOCATION SKULLHOLLOW ORTentative Series
TAXONOMIC CLASS: Loamy-skeletal, mixed, superactive, frigid Vitrandic Argixerolls
TYPICAL PEDON: Skullhollow very cobbly ashy loam, on a north facing 40 percent slope, rangeland. (Colors are for moist soils unless otherwise noted.)
A--0 to 5 inches; black (10YR 2/1) very cobbly ashy loam, very dark gray (10YR 3/1) dry; weak fine granular structure; loose, very friable, nonsticky and nonplastic; many fine and very fine roots; many fine and very fine irregular pores; 50 percent cobbles; neutral (pH 6.8); clear smooth boundary. (3 to 8 inches thick)
AB--5 to 12 inches; black (10YR 2/1) very cobbly ashy loam, very dark grayish brown (10YR 3/2) dry; moderate fine and medium subangular blocky structure; slightly hard, friable, nonsticky and nonplastic; common fine and very fine and few medium roots; many fine and very fine tubular pores; 40 percent cobbles; neutral (pH 7.0); clear smooth boundary. (4 to 10 inches thick)
2Bt1--12 to 17 inches; very dark brown (10YR 2/2) very gravelly clay loam, dark grayish brown (10YR 4/2) dry; moderate medium and coarse subangular blocky structure; hard, firm, slightly sticky and slightly plastic; common fine and very fine and few medium roots; common very fine tubular pores; many faint clay films on faces of peds and in pores; 40 percent gravel and 10 percent cobbles; neutral (pH 7.0); clear smooth boundary.
2Bt2--17 to 24 inches; very dark grayish brown (10YR 3/2) extremely gravelly clay loam, dark grayish brown (10YR 4/2) dry; strong medium subangular blocky structure; very hard, very firm, moderately sticky and moderately plastic; few fine and very fine roots; few fine tubular pores; many distinct clay films on faces of peds and in pores; 65 percent gravel; neutral (pH 7.2); clear smooth boundary.
2Bt3--24 to 28 inches; very dark grayish brown (10YR 3/2) extremely gravelly clay, dark grayish brown (10YR 4/2) dry; strong medium subangular blocky structure; very hard, very firm, moderately sticky and moderately plastic; few fine and very fine roots; few fine tubular pores; many distinct clay films on faces of peds and in pores; 75 percent gravel; neutral (pH 7.2); abrupt wavy boundary. (Combined thickness of the 2Bt horizon ranges from 10 to 25 inches.)
2R--28 inches; basalt.
TYPE LOCATION: Crook County, Oregon; located 2,000 feet north and 600 feet east of the SW corner of section 33, T. 15 S, R. 16 E.
RANGE OF 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 25 to 40 inches. The mollic epipedon is 20 to 30 inches thick. The particle-size control section averages 30 to 35 percent clay. Base saturation is over 75 percent throughout.
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, 15 to 50 percent cobbles, and 0 to 10 percent stones.
The AB horizon has value of 2 or 3 moist, 3 or 4 dry, and chroma of 1 or 2 moist and dry. It is ashy loam or ashy clay loam and contains 0 to 30 percent gravel, 20 to 50 percent cobbles and 20 to 30 percent clay.
The 2Bt horizon has value of 2 or 3 moist, 3 through 5 dry, and chroma of 2 or 3 moist and dry. It is clay loam or clay and contains 35 to 75 percent gravel and 27 to 45 percent clay. Clay texture occur in the horizon immediately above the bedrock.
COMPETING SERIES: These are the Ginserly, Imnaha, Klickson, Millerflat, Needhill, Raycreek, Roundbarn, Saturday, Stemilt, Sycreek, and Wilt series. Imnaha soils are dry in the moisture control section for 60 to 75 days following the summer solstice. Ginserly, Klickson, Needhill, Roundbarn, Saturday, Stemilt, and Sycreek soils are greater than 40 inches to bedrock. Wilt soils have mollic epipedon 7 to 14 inches thick. Raycreek soils are dry for 60 to 75 days and have base saturation; of less than 75 percent. Millerflat soils are moderately well drained and are over 60 inches deep.
GEOGRAPHIC SETTING: Skullhollow soils are on north-facing slopes of mesas at elevations of 3,000 to 4,500 feet. Slopes range from 12 to 60 percent. The soils formed in colluvium and residuum derived from basalt 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, Powellbutte, Searles, and Teguro soils. Anatone soils are shallow and are on adjacent ridgetops of mesas. Bocker soils are very shallow and are on adjacent ridgetops of mesas. Cadlebutte soils are fine and are on adjacent backslopes of mesas. Lickskillet soils are shallow and are on adjacent south-facing sideslopes. Powellbutte soils are fine-loamy. Searles soils are on adjacent south-facing sideslopes. Teguro soils are loamy, shallow and are on adjacent backslopes of mesas.
DRAINAGE AND PERMEABILITY: Well drained, permeability is moderately slow.
USE AND VEGETATION: Skullhollow 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 28 inches (A, AB, and 2Bt horizons)
Argillic horizon - from a depth of 12 to 28 inches (2Bt horizon)
Vitrandic feature - from the surface to a depth of 12 inches (A and AB horizons)