LOCATION MCGREGOR MTTentative Series
TAXONOMIC CLASS: Coarse-silty, mixed, superactive, nonacid, frigid Aquandic Fluvaquents
TYPICAL PEDON: McGregor ashy silt loam (Colors are for moist soil unless otherwise noted.)
A--0 to 5 inches; black (10YR 2/1) ashy silt loam, dark gray (10YR 4/1) dry; moderate fine granular structure; moderately hard, friable, slightly sticky and slightly plastic; few fine and many very fine roots; few fine irregular and many very fine interstitial pores; slightly acid (pH 6.2); clear smooth boundary. (2 to 8 inches thick)
E--5 to 14 inches; dark grayish brown (10YR 4/2) ashy silt loam, light brownish gray (10YR 6/2) dry; moderate thin platy structure; slightly hard, friable, nonsticky and nonplastic; few fine and common very fine roots; few fine tubular and common very fine irregular pores; 10 percent medium worm casts; slightly alkaline (pH 7.4); clear smooth boundary. (6 to 11 inches thick)
2E--14 to 16 inches; grayish brown (2.5Y 5/2) silt loam, light gray (2.5Y 7/2) dry; moderate thin platy structure; moderately hard, friable, nonsticky and nonplastic; common medium roots; common medium irregular pores; neutral (pH 7.2); clear smooth boundary. (2 to 8 inches thick)
2BC--16 to 26 inches; brown (10YR 5/3) very fine sandy loam, light gray (10YR 7/2), dry; massive; slightly hard, friable, nonsticky and nonplastic; few medium roots; common medium irregular pores; 1 percent fine prominent spherical dark yellowish brown (10YR 4/6) moist iron-manganese concretions; neutral (pH 7.0); clear smooth boundary. (0 to 10 inches thick)
3Cg1--26 to 33 inches; grayish brown (2.5Y 5/2) silt loam, light gray (2.5Y 7/2) dry; massive; moderately hard, friable, slightly sticky and slightly plastic; few very fine roots; common medium irregular pores; 1 percent fine prominent spherical dark yellowish brown (10YR 4/6) moist iron-manganese concretions; 1 percent fine spherical carbonate nodules; neutral (pH 7.0); gradual smooth boundary. (0 to 12 inches thick)
3Cg2--33 to 58 inches; light yellowish brown (2.5Y 6/3) silt loam, light gray (2.5Y 7/2) dry; massive; moderately hard, friable, slightly sticky and slightly plastic; few very fine roots; few very fine irregular pores; 2 percent fine prominent spherical dark yellowish brown (10YR 4/6) moist iron-manganese concretions; 1 percent fine spherical carbonate nodules; neutral (pH 7.0); gradual smooth boundary. (9 to 25 inches thick)
3Cg3--58 to 64 inches; light brownish gray (2.5Y 6/2) silt loam, light gray (2.5Y 7/2) dry; massive; slightly hard, very friable, slightly sticky and slightly plastic; few very fine roots; few very fine irregular pores; 5 percent fine prominent spherical dark yellowish brown (10YR 4/6) moist iron-manganese concretions; 5 percent gravel and cobbles; neutral (pH 6.8).
TYPE LOCATION: Flathead County, Montana; 850 feet north and 300 feet east of the southwest corner of section 29, T.28 N., R. 25 W. Dahl Lake topographic quadrangle. UTM zone 11: Northing 5335923, Easting 663303.
RANGE IN CHARACTERISTICS:
Average annual soil temperature - 42 to 45 degrees F.
Depth to seasonal high water table 12 to 24 inches
Volcanic glass content - 5 to 20 percent
Acid-oxalate extractable Al + 1/2 Fe - 0.4 to 1.0 percent
Moist bulk density - 1.0 to 1.2 g/cc
Ap or A horizon
Hue 10YR
Value - 3, 4, or 5 dry, 2 or 3 moist
Chroma - 1 or 2
Texture ashy silt loam
Clay content 10 to 18 percent
Bulk density - 1.0 to 1.2 g/cm3
Volcanic glass - 5 to 20 percent
Acid oxalate extractable Al + 1/2Fe - 0.4 to 1.0 percent
Reaction - pH 6.2 to 7.8
E horizon
Hue 10YR
Value 5, 6 or 7 dry, 3, 4, or 5 moist
Chroma - 1 or 2
Texture ashy silt loam
Clay content 10 to 18 percent
Bulk density - 1.0 to 1.2 g/cm3
Volcanic glass - 5 to 20 percent
Acid oxalate extractable Al + 1/2Fe - 0.4 to 1.0 percent
Reaction - pH 6.2 to 7.8
2E horizon
Hue 10YR or 2.5Y
Value 6, 7, or 8 dry, 4, 5, or 6 moist
Chroma 1 or 2
Texture silt loam or very fine sandy loam
Clay content 8 to 18 percent
Reaction pH 6.6 to 7.8
2BC horizon
Hue 10YR or 2.5Y
Value 6, 7, or 8 dry, 4, 5, or 6 moist
Chroma 1 to 3
Texture silt loam, very fine sandy loam, loamy very fine sand, or silt
Clay content 6 to 18 percent
Reaction - pH 6.8 to 7.8
3Cg horizons
Hue 2.5Y, 5Y, or 10Y
Value 6, 7, or 8 dry, 4, 5, 6, or 7 moist
Chroma 2 or 3
Texture - silt loam, very fine sandy loam, loamy very fine sand, or silt
Clay content 6 to 18 percent
Reaction pH 6.6 to 7.8
Rock fragments 0 to 5 percent gravel and cobbles
COMPETING SERIES: There are no competing series.
GEOGRAPHIC SETTING:
Landform - flood plains and closed depressions.
Elevation 3,100 to 4,100 feet.
Slope - 0 to 2 percent.
Parent material volcanic ash over mixed lacustrine sediments and alluvium.
Climate - long, cold winters; moist springs; warm, dry summers.
Mean annual precipitation 15 to 25 inches, much of which falls as snow and spring rain.
Mean annual air temperature - 38 to 47 degrees F.
Frost-free period - 70 to 95 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Meadowpeak, Blackcreek, Tallcreek, Dahlake, Blacklake, McLangor, and Barzee soils. Meadowpeak soils are on floodplains and closed depressions but do not have volcanic ash in the surface layer. Blackcreek and Tallcreek soils are on stream terraces and have cambic horizons and lime in the subsoil. Dahlake(T) soils are on lake terraces and have high SAR values. Blacklake, McLangor, and Barzee soils are on floodplains and closed depressions, are very poorly drained, and have organic soil materials.
DRAINAGE AND PERMEABILITY: Poorly drained, moderate permeability.
USE AND VEGETATION: These soils are used for rangeland, wildlife habitat, and watershed. Potential natural vegetation is mainly shrubby cinquefoil, quaking aspen, basin wildrye, reed canarygrass, field horsetail, and other perennial grasses and sedges.
DISTRIBUTION AND EXTENT: McGregor soils are of limited extent in the valleys of northwestern Montana. MLRA 44A.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana
SERIES PROPOSED: Flathead County, Montana, 2004. McGregor is the name of a lake in the survey area.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - 0 to 7 inches mixed (A and E horizons);
Particle-size control section - 10 to 40 inches (E, 2E, 2BC, 3Cg1, and 3Cg2 horizons).
McGregor soils have a frigid temperature regime and an aquic moisture regime