LOCATION PENSORE MT+CO WY UTEstablished Series
TAXONOMIC CLASS: Loamy-skeletal, carbonatic, frigid Lithic Calciustepts
TYPICAL PEDON: Pensore gravelly loam, in grassland (colors are for dry soil unless otherwise noted).
A--0 to 4 inches; grayish brown (10YR 5/2) gravelly loam, very dark grayish brown (10YR 3/2) moist; moderate very fine granular structure; soft, very friable, slightly sticky and slightly plastic; many very fine roots; 20 percent angular pebbles; disseminated lime; strongly effervescent; moderately alkaline (pH 8.0); clear smooth boundary. (2 to 7 inches thick)
Bk--4 to 15 inches; light gray (10YR 7/2) very gravelly loam, pale brown (10YR 6/3) moist; weak medium subangular blocky structure; slightly hard, very friable, slightly sticky and slightly plastic; common very fine roots; many very fine tubular and interstitial pores; 45 percent angular pebbles, 15 percent angular cobbles; disseminated lime; continuous faint lime coating on top of coarse fragments; continuous prominent lime casts on undersides of coarse fragments; violently effervescent; moderately alkaline (pH 8.2); gradual wavy boundary. (7 to 15 inches thick)
R--15 inches; hard limestone bedrock with a few fractures; few very fine roots in fractures.
TYPE LOCATION: Lewis and Clark County, Montana; 500 feet east and 400 feet south of the NW corner of sec. 30, T. 10 N., R. 4 W.
RANGE IN CHARACTERISTICS:
Soil moisture: The soil moisture control section is between 4 and 12, or from 4 inches to the lithic contact. In Montana, the Pensore soils have soil moisture control sections that are affected by significant precipitation peaks in the spring and early summer. Ustic soil moisture regime bordering on aridic.
Soil temperature: 40 to 47 degrees F.
Depth to lithic contact: 10 to 20 inches to limestone bedrock
Depth to secondary calcium carbonate: 2 to 7 inches
The surface layer, where mixed to a depth of 7 inches, will not meet the requirements for a mollic epipedon.
Phases- cool, cobbly.
Particle-size control section (weighted average): clay content : 10 to 27 percent; rock fragments: 35 to 80 percent
A horizon
Hue: 7.5YR to 2.5Y
Value: 4 to 6 dry; 3, 4, or 5 moist
Chroma: 1 to 4
Texture: sandy loam, loam or sandy clay loam
Clay content: 10 to 27 percent
Rock fragments: 15 to 60 percent--0 to 15 percent stones and cobbles; 10 to 55 percent gravel and channers
Reaction: pH 7.4 to 8.4
Bk horizon:
Hue: 7.5YR to 2.5Y
Value: 5 to 8 dry, 4 to 7 moist
Chroma: 2 to 6
Texture: loam, fine sandy loam, sandy loam
Clay content: 10 to 27 percent
Rock fragments: 35 to 80 percent - 10 to 35 percent cobbles and stones; 20 to 60 percent gravel and channers
Calcium carbonate equivalent: 40 to 60 percent, including coarse fragments less than 3/4-inch in size
Reaction: pH 7.9 to 9.6
COMPETING SERIES: This is the Warneke (MT) series. Warneke soils have typic ustic soil moisture regime.
GEOGRAPHIC SETTING:
Landform - bedrock-floored plains; hills; hillslopes; valleys; mesas; mountains
Elevation - 3,500 to 6,500 feet. In Colorado and Utah the elevations range from 6,300 to 8,500 feet
Slope - 2 to 75 percent
Parent material - colluvium and residuum derived from limestone
Climate - long, cold winters; moist springs; warm summers
Mean annual precipitation - 10 to 16 inches
Mean annual temperature - 38 to 45 degrees F.
Frost-free period - 75 to 120 days
GEOGRAPHICALLY ASSOCIATED SOILS:
DRAINAGE AND PERMEABILITY: Well drained; moderate permeability.
USE AND VEGETATION: Pensore soils are used mainly for rangeland. Potential native vegetation is mainly bluebunch wheatgrass, needleandthread, forbs, and shrubs.
DISTRIBUTION AND EXTENT: Pensore soils are of moderate extent in southwestern Montana, Colorado, Utah and Wyoming.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana
SERIES ESTABLISHED: Lewis and Clark County, Montana, 1992.
REMARKS: Soil interpretation records: MT0149, MT1005, MT1094 and MT1679, MT3163. Diagnostic horizons and features recognized in this pedon are:
Particle-size control section: The zone from 10 to 15 inches (Bk horizon).
Ochric epipedon: The zone from the soil surface to 4 inches (A horizon).
Calcic horizon: The zone from 4 to 15 inches (Bk horizon).
Lithic contact: The contact with limestone bedrock at 15 inches (R layer).
Classification changed from Borollic Lithic Calciorthids to Lithic Ustochrepts in 1994.
Classification changed from Lithic Ustochrepts to Aridic Lithic Ustochrepts in 1997.
Classification changed from Aridic Lithic Ustochrepts to Lithic Calciustepts in 1998.
Taxonomic version: Eighth Edition, 1998.