LOCATION TOBINCREEK MTTentative Series
TAXONOMIC CLASS: Fine, smectitic Ustic Argicryolls
TYPICAL PEDON: Tobincreek loam, forested on a north-facing slope of 40 percent at 5,920 feet elevation. When described on September 15, 1988 the soil was slightly moist below a depth of 8 inches (colors are for air dry soil unless otherwise noted).
Oi--0 to 2 inches; slightly decomposed plant material; clear smooth boundary. (0 to 3 inches thick)
A--2 to 6 inches; dark grayish brown (10YR 4/2) loam, very dark brown (10YR 2/2) moist; weak fine granular structure; hard, friable, slightly sticky and slightly plastic; many very fine, fine, medium and many coarse roots; common very fine and fine and few medium irregular pores; 5 percent gravel and 5 percent cobbles; neutral (pH 7.0); clear smooth boundary. (3 to 10 inches thick)
Bt1--6 to 12 inches; brown (10YR 4/3) gravelly clay loam, dark brown (10YR 3/3) moist; moderate medium angular blocky structure; hard, firm, moderately sticky and moderately plastic; many very fine, fine, medium and coarse roots; common fine and few medium and coarse irregular pores; 10 percent patchy, distinct clay films along root channels; 10 percent gravel and 5 percent cobbles; neutral (pH 6.8); clear smooth boundary.
Bt2--12 to 25 inches; yellowish brown (10YR 5/4) gravelly clay, brown (10YR 4/3) moist; moderate medium angular blocky structure; hard, firm, moderately sticky and moderately plastic; many very fine, fine, medium and coarse roots; few fine and medium irregular pores; 25 percent patchy, distinct clay films on vertical faces of peds and on surfaces of pores; 20 percent gravel and 5 percent cobbles; neutral (pH 6.8); abrupt smooth boundary. (combined thickness of the Bt horizons is 13 to 26 inches thick)
Cr1--25 to 44 inches; brown (10YR 5/3) semi-consolidated brittle siltstone and fine grained sandstone bedrock; slightly effervescent; slightly alkaline (pH 7.6); clear smooth boundary.
R--44 to 60 inches; pale brown (10YR 6/3), consolidated, very hard, very brittle siltstone and sandstone bedrock; slightly effervescent; slightly alkaline (pH 7.8);
TYPE LOCATION: Park County, Montana; 700' west and 700' south of the north east corner of Section 36, Township 2N, Range 10E.
RANGE IN CHARACTERISTICS:
Soil temperature - 36 to 40 degrees F.
Moisture control section 4 to 12 inches.
Depth to paralithic contact - 20 to 40 inches.
Depth to lithic contact 40 to 60 inches.
Depth to calcareous material - 20 to 40 inches.
Mollic epipedon thickness - 9 to 14 inches.
A horizon
Value: 3 or 4 dry, 2 or 3 moist
Chroma: 1 to 3, dry or moist
Clay content: 18 to 27 percent
Rock fragments: 5 to 10 percent 0 to 10 percent gravel, 0 to 5 percent cobbles
Reaction: pH 6.1 to 7.3
Bt horizons
Value: 4 to 6 dry, 3 to 5 moist
Chroma: 2 to 4, dry or moist
Texture: clay loam or clay
Clay content: 35 to 45 percent
Rock fragments: 5 to 35 percent 5 to 30 percent gravel, 0 to 5 percent cobbles.
Reaction: pH 6.3 to 7.4
COMPETING SERIES:
Florissant (CO) - has a strongly cemented Bk horizon at 15 to 30 inches.
Goth (CO) is very deep.
Gothic (CO) - is very deep.
Jerry (CO) - is very deep.
Judy (CO) - has a lithic contact at 20 to 40 inches.
Mayoworth (WY) - has a BA horizon.
Owen Creek (WY) - has horizons of secondary carbonate accumulation.
Parlin (CO) - is very deep.
Piltz (CO) has 5 to 35 percent granite rock fragments in the argillic horizon.
Sneffels (WY) has a lithic contact at 20 to 40 inches.
GEOGRAPHIC SETTING:
Landform Mountain slopes, stream terrace risers and hills.
Elevation 5,500 to 6,500 feet
Slope 15 to 45 percent
Parent material Calcareous siltstone, shale and sandstone
Mean annual air temperature - 34 to 38 degrees F.
Mean annual precipitation - 18 to 20 inches
Frost-free period 50 to 70 days
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Doby and Mayflower soils. Doby soils are shallow to a paralithic contact and are on sedimentary plains and hills. Mayflower soils are pachic and are on hills, ridges, stream terraces, and mountain slopes.
DRAINAGE AND PERMEABILITY: Well-drained; slow permeability.
USE AND VEGETATION: Used mostly for understory grazing. Dominant natural vegetation is Douglas fir, pinegrass, serviceberry, common snowberry, bearded wheatgrass, rose, brome, Idaho fescue, Kentucky bluegrass and some bluebunch wheatgrass. Engelmann spruce, Rocky Mountain maple, aspen, juniper and cottonwood occupy small areas.
DISTRIBUTION AND EXTENT: Tobincreek soils are of small extent in south western Montana. MLRA 43B.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana
SERIES PROPOSED: Park County, Montana, 2005. Tobincreek soils are named after a nearby feature on the Ibex Mountain quadrangle.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon the zone from 2 to 12 inches (A and Bt1)
Argillic horizon the zone from 6 to 25 inches (Bt1 and Bt2)
Particle-size control section the zone from 6 to 25 inches (Bt1 and Bt2)
Paralithic contact at 25 inches (Cr)
Lithic contact at 44 inches (R)
Tobincreek soils have an ustic moisture regime and a cryic temperature regime.