LOCATION RIVERRUN MT
Established Series
Rev. TJK-KTS-RJS
04/2013
RIVERRUN SERIES
The Riverrun series consists of very deep, moderately well drained soils that formed in alluvium or outwash. These soils are on flood plains, flood-plain steps, stream terraces, outwash fans and drainageways. Slopes are 0 to 4 percent. Mean annual precipitation is about 300 mm. Mean annual air temperature is about 5.5 degrees C.
TAXONOMIC CLASS: Sandy-skeletal, mixed, frigid Oxyaquic Ustifluvents
TYPICAL PEDON: Riverrun gravelly sandy loam, in native grass (colors are for dry soil unless otherwise noted).
A--0 to 10 cm; dark grayish brown (10YR 4/2) gravelly sandy loam, very dark brown (10YR 2/2) moist; weak medium granular structure; slightly hard, very friable, nonsticky and nonplastic; many very fine and common fine roots; many very fine and common fine interstitial pores; 15 percent gravel; neutral (pH 6.8); abrupt smooth boundary. (5 to 15 cm thick)
C1--10 to 23 cm; light brownish gray (10YR 6/2) gravelly loamy sand, grayish brown (10YR 5/2) moist; single grain; loose, nonsticky and nonplastic; common very fine and few fine roots; many very fine interstitial pores; 20 percent gravel; neutral (pH 7.2); clear smooth boundary. (8 to 38 cm thick)
C2--23 to 145 cm; light brownish gray (10YR 6/2) very gravelly loamy coarse sand, grayish brown (10YR 5/2) moist; single grain; loose, nonsticky and nonplastic; few very fine and fine roots; 50 percent gravel; neutral (pH 7.2); gradual wavy boundary. (75 to 140 cm thick)
C3--145 to 152 cm; light brownish gray (2.5Y 6/2) loamy sand, dark grayish brown (2.5Y 4/2) moist; single grain; loose, nonsticky and nonplastic; few very fine roots; slightly alkaline (pH 7.8).
TYPE LOCATION: Jefferson County, Montana; 640 meters north and 350 meters west of the southeast corner of sec. 2, T1N, R4W.
RANGE IN CHARACTERISTICS:
Soil temperature - 4.4 to 7.8 degrees C.
Depth to a seasonally high water table - 100 to 150 cm for extended periods during portions of the late spring or early summer
Particle-size control section (weighted average) - 35 to 70 percent rock fragments
Note: The surface layer, when mixed to 7 inches does not meet the requirements for a mollic epipedon. Thin dark colored buried horizons occur in some pedons.
A horizon
Hue: 10YR or 2.5Y; dry or moist
Value: 4 to 7 dry; 2 to 5 moist
Chroma: 2 or 3; dry or moist
Texture: loam, sandy loam, coarse sandy loam, fine sandy loam or loamy sand
Clay content: 6 to 26 percent
Rock fragments: 0 to 50 percent--0 to 40 percent gravel, 0 to 10 percent cobbles and stones
Calcium carbonate equivalent: 0 to 30 percent
Electrical conductivity: 0 to 4 mmhos/cm;
Sodium adsorption ratio: 0 to 13
Reaction: pH 6.6 to 7.8
Saline phase
Electrical conductivity: 4 to 27 mmhos/cm
Sodium adsorption ratio: 13 to 30
Reaction: pH 7.9 to 9.0
C1 horizon
Hue: 10YR or 2.5Y; dry or moist
Value: 5 to 7 dry; 4 or 5 moist
Chroma: 2 or 3; dry or moist
Texture: sand, loamy sand, loamy coarse sand or coarse sand
Clay content: 2 to 15 percent
Rock fragments: 0 to 75 percent--0 to 45 percent gravel, 0 to 30 percent cobbles and stones
Calcium carbonate equivalent: 0 to 15 percent
Electrical conductivity: 0 to 4 mmhos/cm
Sodium adsorption ratio: 0 to 13
Reaction: pH 6.6 to 8.4
Saline phase
Reaction: pH 7.4 to 9.0
C2 horizon
Hue: 10YR or 2.5Y; dry or moist
Value: 5 to 7 dry; 4 or 5 moist
Chroma: 2 or 3; dry or moist
Texture: stratified sand, loamy sand, loamy coarse sand or coarse sand
Clay content: 2 to 10 percent
Rock fragments: 35 to 80 percent--35 to 70 percent gravel, 0 to 20 percent cobbles and stones
Calcium carbonate equivalent: 0 to 15 percent
Electrical conductivity: 0 to 4 mmhos/cm
Sodium adsorption ratio: 0 to 13
Reaction: pH 6.6 to 8.4
C3 horizon
Hue: 10YR or 2.5Y; dry or moist
Value: 5 to 7 dry; 4 or 5 moist
Chroma: 2 or 3; dry or moist
Texture: sand, loamy sand, loamy coarse sand or coarse sand
Clay content: 2 to 15 percent
Rock fragments: 0 to 75 percent--0 to 45 percent gravel, 0 to 30 percent cobbles and stones
Calcium carbonate equivalent: 0 to 15 percent
Electrical conductivity: 0 to 4 mmhos/cm
Sodium adsorption ratio: 0 to 13
Reaction: pH 6.6 to 8.4
COMPETING SERIES: There are no competing series.
GEOGRAPHIC SETTING:
Landform - flood plains, flood plain steps, stream terraces, outwash fans and drainageways
Elevation - 1,025 to 1,675 meters
Slope - 0 to 4 percent
Parent material - alluvium or outwash
Climate - long, cold winters; moist springs; warm summers
Mean annual precipitation - 250 to 400 mm
Mean annual air temperature - 3.2 to 6.5 degrees C.
Frost-free period - 70 to 115 days
GEOGRAPHICALLY ASSOCIATED SOILS: None listed.
DRAINAGE AND PERMEABILITY: Moderately well drained; rapid permeability.
USE AND VEGETATION: These soils are used primarily for pasture, rangeland, and wildlife habitat. The potential native vegetation is mainly bluebunch wheatgrass, basin wildrye, prairie sandreed, Sandberg bluegrass, snowberry, and woods rose. Groves of cottonwood trees and willows occur in some areas.
DISTRIBUTION AND EXTENT: The Riverrun series is of moderate extent in the intermountain valleys of central and southwestern Montana. MLRAs - 44A, 44B.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana.
SERIES ESTABLISHED: Jefferson County, Montana, 1998.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - from 0 to 10 cm (A horizon)
Particle-size control section - from 25 to 100 cm (part of C2 horizon)
Riverrun soils have a frigid temperature regime, an ustic moisture regime and an oxyaquic moisture subclass.
ADDITIONAL DATA: Soil interpretations records - MT1582, MT1583.
National Cooperative Soil Survey
U.S.A.