LOCATION LARKSPUR MTEstablished Series
TAXONOMIC CLASS: Loamy-skeletal, mixed, superactive, nonacid Lithic Cryorthents
TYPICAL PEDON: Larkspur very cobbly coarse sandy loam, in rangeland on a 19 percent slope at 1,717 meters elevation colors are for dry soil unless otherwise indicated).
A--0 to 8 cm; pale brown (10YR 6/3) very cobbly coarse sandy loam, brown (10YR 4/3) moist; moderate medium granular structure; very friable, slightly hard, nonsticky and nonplastic; common fine and few medium roots; many fine interstitial pores; 25 percent gravel, 20 percent cobbles; slightly acid (pH 6.4); clear smooth boundary. (8 to 28 cm thick)
C--8 to 20 cm; light gray (10YR 7/2) very cobbly coarse sandy loam, grayish brown (10YR 5/2) moist; single grain; loose, nonsticky and nonplastic; few fine roots; common fine nterstitial pores; 30 percent gravel, 25 percent cobbles; neutral (pH 6.8); abrupt irregular boundary.
R--20 to 152 cm; fractured gray rhyolitic tuff.
TYPE LOCATION: Ramsay topographic quadrangle, Silver Bow County, Montana; 85 meters south and 465 meters west of the NE corner of section 12, T. 3 N., R. 9 W. UTM Zone 12: 371648e, 5098927n, NAD 83.
RANGE IN CHARACTERISTICS:
Soil temperature - 2 to 6 degrees C
Moisture control section - 10 cm to the top of the bedrock contact
Depth to bedrock - 15 to 25 cm
Surface fragments - 0 to 10 percent stones
A horizon
Value: 4 to 6 dry; 3 to 5 moist
Chroma: 3 or 4 dry or moist
Texture: coarse sandy loam, sandy loam, loam
Clay content: 10 to 20 percent
Rock fragments: 35 to 80 percent--15 to 60 percent gravel, 0 to 30 cobbles, 0 to 15 percent stones
Reaction: pH 5.4 to 6.8
C horizon
Value: 5 to 7 dry; 4 or 5 moist
Chroma: 2 to 4 dry or moist
Texture: coarse sandy loam, sandy loam
Clay content: 8 to 20 percent
Rock fragments: 35 to 85 percent--15 to 70 percent gravel; 0 to 30 percent cobbles; 0 to 10 percent stones
Reaction: pH 5.8 to 7.3
COMPETING SERIES: There are no competing series.
GEOGRAPHIC SETTING:
Landform - mountains, hills and ridges on structural benches
Elevation - 1,560 to 2,289 meters
Slope - 4 to 70 percent
Parent material - colluvium and/or residuum over rhyolite, rhyodacite, or rhyolitic tuff
Climate - long, cold winters; cold, moist springs; short, cool summers
Mean annual precipitation - 305 to 483 millimeters, much of which falls as snow and as spring rain
Mean annual air temperature - 1 to 5 degrees centigrade
Frost-free period - 30 to 70 days
GEOGRAPHICALLY ASSOCIATED SOILS: Associated soils which occur on similar landforms are the
Poin,
Hungryhill and
Bigbutte series. Poin soils are shallow to bedrock and have a mollic epipedon. Hungryhill soils are moderately deep to bedrock and have a zone of clay accumulation. Bigbutte soils are moderately
deep and have an ashy particle-size family.
DRAINAGE AND PERMEABILITY: Well drained; moderately rapid permeability.
USE AND VEGETATION: Larkspur soils are used mainly for grazing; vegetation is chiefly mixed grasses, such as Bluebunch Wheatgrass and Idaho fescue with some areas of widely scattered Douglas fir and Rocky Mountain Juniper.
DISTRIBUTION AND EXTENT: Larkspur soils are of small extent in the intermontane basins of central Montana. MLRA 43.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana.
SERIES ESTABLISHED: Silver Bow County, Montana, 2007.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - from 0 to 8 cm (A horizon)
Particle-size control section - from 0 to 20 cm (A and C horizons)
Larkspur soils have a cryic temperature regime and an ustic moisture regime.