LOCATION PIEGAN MT
Tentative Series
Rev. PHO-JMS-RJS
01/2023
PIEGAN SERIES
The Piegan series consists of moderately deep, well drained soils that formed in colluvium or till over residuum. These soils occur on nivation hollows on ridges, mountain slopes and glacial-valley walls. Slopes are 8 to 35 percent. The mean annual precipitation is about 1,825 mm and the mean annual temperature is about 2.0 degrees C.
TAXONOMIC CLASS: Loamy-skeletal, mixed, superactive Typic Haplocryolls
TYPICAL PEDON: Piegan extremely cobbly sandy loam, in alpine meadow. This profile was describe on a 25 percent slope at 2,276 meters elevation. (Colors are for dry soil unless otherwise stated.)
A1--0 to 7 cm; dark gray (10YR 4/1) extremely cobbly sandy loam, black (10YR 2/1) moist; weak fine granular structure; soft, very friable, nonsticky and nonplastic; many very fine and common fine roots; common very fine tubular and irregular pores; 40 percent gravel, 20 percent cobbles, 10 percent stones; neutral (pH 6.6); clear smooth boundary.
A2--7 to 17 cm; dark gray (10YR 4/1) extremely gravelly sandy loam, black (10YR 2/1) moist; weak fine granular structure; soft, very friable, nonsticky and nonplastic; common very fine and few fine roots; common very fine tubular and irregular pores; 55 percent gravel, 20 percent cobbles, 10 percent stones; slightly acid (pH 6.5); clear smooth boundary.
Bw1--17 to 26 cm; brown (10YR 5/3) extremely cobbly sandy loam, dark brown (10YR 3/3) moist; weak fine subangular blocky structure; soft, very friable, slightly sticky and slightly plastic; common very fine and few fine roots; common very fine irregular pores; 50 percent gravel, 25 percent cobbles, 10 percent stones; slightly acid (pH 6.1); clear smooth boundary.
Bw2--26 to 77 cm; light brownish gray (10YR 6/2) extremely cobbly sandy loam, dark grayish brown (10YR 4/2) moist; weak fine subangular blocky structure; soft, very friable, slightly sticky and slightly plastic; few very fine roots; few very fine irregular pores; 30 percent gravel, 40 percent cobbles, 10 percent stones; slightly acid (pH 6.3); abrupt smooth boundary.
2R--77 cm; argillite bedrock.
TYPE LOCATION: Glacier County, Montana; 515 meters south and 613 meters east of the northwest corner of sec. 5, T. 31N, R. 13W; Latitude - 48 degrees, 28 minutes, 44 seconds north; Longitude - 113 degrees, 19 minutes, 33 seconds west, NAD 1983.
RANGE IN CHARACTERISTICS:
Mean annual soil temperature - 1.0 to 5.0 degrees C.
Mollic epipedon thickness - 18 to 38 cm
Depth to a lithic contact - 50 to 100 cm
Particle-size control section - averages 5 to 18 percent clay
A1, A2 horizons
Hue: 10YR, 7.5YR or 2.5YR
Value: 3 to 5 dry; 2 or 3 moist
Chroma: 1 or 2 dry or moist
Texture (less than 2mm fraction): loam or sandy loam
Clay content: 6 to 20 percent
Rock fragments: 35 to 85 percent--20 to 55 percent gravel and/or channers, 0 to 20 percent cobbles and/or flagstones and 0 to 10 percent stones
Reaction: pH 5.8 to 7.0
Thickness (A1, A2 combined): 16 to 25 cm
Bw1, Bw2 horizons
Hue: 10YR, 7.5YR or 2.5YR
Value: 3 to 6; dry or moist
Chroma: 2 or 4; dry or moist
Texture (less than 2mm fraction): loam or sandy loam
Clay content: 6 to 18 percent
Rock fragments: 35 to 80 percent--25 to 60 percent gravel and/or channers, 5 to 40 percent cobbles and/or flagstones, 5 to 20 percent stones and 0 to 5 percent boulders
Reaction: pH 5.8 to 7.0
Thickness (B1, Bw2 combined): 30 to 70 cm
C horizon
Texture (less than 2mm fraction): sandy loam or coarse sandy loam
Clay content: 5 to 15 percent
Rock fragments: 35 to 85 percent--35 to 60 percent gravel and/or channers, 10 to 40 percent cobbles and/or flagstones, 5 to 20 percent stones and 0 to 5 percent boulders
Reaction: pH 5.8 to 7.0
Thickness: 0 to 25 cm
COMPETING SERIES:
Broad Canyon (UT) -- are very deep
Kamack (UT) -- are deep to a lithic contact
Longabaugh (UT) -- are very deep
Midfork (WY) -- have a calcareous subsoil
Sawpit (CO) -- are very deep
GEOGRAPHIC SETTING:
Landform -- nivation hollows on ridges, mountain slopes and glacial-valley walls
Elevation -- 1,600 to 2,600 meters
Slope -- 8 to 35 percent
Parent material -- colluvium or till over residuum
Climate -- long, cold winters; moist springs; short warm summers
Mean annual precipitation -- 1,000 to 2,500 mm
Mean annual air temperature -- 0.0 to 4.0 degrees C.
Frost-free period -- 25 to 50 days
GEOGRAPHICALLY ASSOCIATED SOILS: None listed.
DRAINAGE AND PERMEABILITY: Well drained and moderate permeability (15 to 50 um/sec).
USE AND VEGETATION: Piegan soils are used mainly for recreation and wildlife habitat. The vegetation is dominated by Payson's sedge, northern singlespike sedge, black alpine sedge, Parry's rush, bristleleaf sedge, Hitchcock's smooth woodrush and subalpine fleabane.
DISTRIBUTION AND EXTENT: Mountains of northwestern Montana. The series is of small extent. MLRA 43A and 43B.
SOIL SURVEY REGIONAL OFFICE (SSRO) RESPONSIBLE: Bozeman, Montana.
SERIES PROPOSED: Glacier National Park area; Glacier County, Montana 2015.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon -- 0 to 26 cm (A1, A2, Bw1 horizons)
Cambic horizon -- 26 to 77 cm (Bw2 horizon)
Lithic contact - 77 cm (2R horizon)
Particle-size control section -- 25 to 77 cm (part of the Bw1, Bw2 horizons)
Piegan soils have a cryic temperature regime and an udic moisture regime.
Taxonomic version: Twelfth Edition, 2014.
National Cooperative Soil Survey
U.S.A.