LOCATION SWANPEAK IDEstablished Series
TAXONOMIC CLASS: Clayey-skeletal, smectitic, frigid Vertic Argixerolls
TYPICAL PEDON: Swanpeak cobbly loam; rangeland. (Colors are for dry soil unless otherwise noted.)
A1--0 to 6 inches; dark grayish brown (10YR 4/2) cobbly loam, very dark brown (10YR 2/2) moist; strong fine granular structure; slightly hard, very friable, slightly sticky and slightly plastic; common very fine and few fine roots; many very fine irregular pores; 10 percent gravel and 10 percent cobbles; neutral (pH 7.0); abrupt smooth boundary. (2 to 8 inches thick)
A2--6 to 15 inches; dark grayish brown (10YR 4/2) silty clay loam, very dark brown (10YR 2/2) moist; strong medium granular structure; slightly hard, very friable, moderately sticky and moderately plastic; common very fine, few fine and medium roots; many very fine, common fine and medium irregular pores; 10 percent gravel; neutral (pH 6.9); clear wavy boundary. (5 to 12 inches thick)
AB--15 to 18 inches; brown (10YR 4/3) cobbly silty clay loam, dark brown (10YR 3/3) moist; strong fine granular structure; slightly hard, very friable, moderately sticky and moderately plastic; common very fine roots; many very fine tubular and common very fine irregular pores; common faint clay films on faces of peds; 10 percent gravel and 15 percent cobbles; neutral (pH 7.2); clear wavy boundary. (0 to 9 inches thick)
Bt1--18 to 24 inches; brown (7.5YR 5/4) very cobbly clay, brown (7.5YR 4/4) moist; moderate coarse prismatic structure parting to strong medium subangular blocky; hard, friable, moderately sticky and very plastic; common very fine and few fine roots; common very fine tubular and irregular pores; many prominent clay films on faces of peds; 15 percent gravel and 20 percent cobbles; neutral (pH 7.2); clear wavy boundary. (3 to 13 inches thick)
Bt2--24 to 35 inches; light brown (7.5YR 6/4) very cobbly clay, brown (7.5YR 4/4) moist; moderate coarse prismatic structure parting to strong medium subangular blocky; hard, friable, very sticky and very plastic; few very fine and fine roots; common very fine tubular and irregular pores; many prominent clay films on faces of peds; 15 percent gravel, 20 percent cobbles and 5 percent stones; neutral (pH 7.2); clear wavy boundary. (5 to 18 inches thick)
Bt3--35 to 60 inches; light brown (7.5YR 6/4) extremely cobbly clay, brown (7.5YR 5/4) moist; strong medium subangular blocky structure; very hard, firm, very sticky and very plastic; few very fine roots; common very fine irregular and few very fine tubular pores; many prominent clay films on faces of peds; 20 percent gravel, 35 percent cobbles and 10 percent stones; neutral (pH 7.3).
TYPE LOCATION: Bear Lake County, Idaho; approximately 5 miles south of St. Charles; about 50 feet north and 300 feet east of the southwest corner of section 15, T. 16 S., R. 43 E.; USGS St. Charles 7.5 minute topographic quadrangle; 42 degrees 01 minutes 47 seconds north latitude and 111 degrees 25 minutes 21 seconds west longitude, NAD 27.
RANGE IN CHARACTERISTICS:
Soil moisture control section - usually moist, dry in all parts for 45 consecutive days or more in the four months following the summer solstice. Xeric moisture regime.
Mollic epipedon thickness - 14 to 18 inches (may extend into the Bt horizon)
Depth to calcic horizon - 40 to greater than 60 inches
Some pedons have a Btk or Btkss horizon below 40 inches
Average annual soil temperature - 41 to 44 degrees F.
Particle-size control section:
Clay content - 35 to 55 percent
Rock fragments - averages 35 to 70 percent fragments of mixed lithology (5 to 15 percent gravel, 10 to 40 percent cobbles, and 0 to 35 percent stones)
Surface rock fragments - 0 to 15 percent
A1 horizon
Hue - 7.5YR or 10YR
Value - 4 or 5 dry, 2 or 3 moist
Chroma - 2 or 3 dry or moist
Texture - loam, silt loam or their gravelly, very gravelly, cobbly, very cobbly, stony, or very stony analogues
Clay content - 20 to 26 percent
Rock fragments - 10 to 50 percent total (5 to 15 percent gravel, 5 to 30 percent cobbles and 0 to 35 percent stones)
Reaction - neutral (pH 6.6 to 7.3)
A2 horizon
Hue - 7.5YR or 10YR
Value - 4 or 5 dry, 2 or 3 moist
Chroma - 2 or 3 dry or moist
Texture - silty clay loam, clay loam or their gravelly, very gravelly, cobbly, very cobbly, stony, or very stony analogues
Clay content - 28 to 35 percent
Rock fragments - 10 to 50 percent total (5 to 15 percent gravel, 5 to 30 percent cobbles and 0 to 35 percent stones)
Reaction - neutral (pH 6.6 to 7.3)
AB horizon (when present) (some pedons may have A/B, BA or B/A horizons)
Hue - 7.5YR or 10YR
Value - 4 or 5 dry, 2 or 3 moist
Chroma - 2 or 3 dry or moist
Texture - gravelly silty clay loam, gravelly clay loam or their very gravelly, cobbly, very cobbly, extremely cobbly, stony, very stony, or extremely stony analogues
Clay content - 28 to 35 percent
Rock fragments - 20 to 70 percent total (5 to 15 percent gravel, 5 to 40 percent cobbles and 0 to 35 percent stones)
Reaction - neutral (pH 6.6 to 7.3)
Bt horizons (some pedons may have Btss horizons)
Hue - 5YR, 7.5YR, or 10YR
Value - 4 to 6 dry, 4 or 5 moist
Chroma - 4 to 6 dry or moist
Texture - very cobbly silty clay loam, very cobbly clay loam, very cobbly silty clay, very cobbly clay or their extremely cobbly, very stony, or extremely stony analogues
Clay content - 35 to 55 percent
Rock fragments - 35 to 70 percent total (5 to 15 percent gravel, 10 to 40 percent cobbles and 0 to 35 percent stones)
Reaction - neutral (pH 6.6 to 7.3)
Btk or Btkss horizon (when present)
Hue - 5YR, 7.5YR, or 10YR
Value - 5 or 6 dry, 4 to 6 moist
Chroma - 3 or 4 dry, or moist
Texture - very cobbly silty clay loam, very cobbly clay loam, very cobbly silty clay, very cobbly clay or their extremely cobbly, very stony, or extremely stony analogues
Clay content - 35 to 50 percent
Rock fragments - 40 to 75 percent total (5 to 15 percent gravel, 10 to 40 percent cobbles and 0 to 35 percent stones)
Reaction - neutral or slightly alkaline (pH 6.6 to 7.8)
COMPETING SERIES: This is the Tuscor (T) series. Tuscor soils are deep to bedrock and were formed in colluvium and residuum derived from rhyolite.
GEOGRAPHIC SETTING:
Landform - hillslopes, mountain slopes, summits, alluvial fans, and fan remnants
Elevation - 5,900 to 7,200 feet
Slope - 1 to 35 percent
Parent material - silty and clayey alluvium from mixed sources
Climate - long, cold winters; moist springs; warm, dry summers
Average annual precipitation - 14 to 24 inches
Average annual temperature - 37 to 43 degrees F.
Frost-free period - 65 to 95 days
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Ant Flat, Dutchcanyon (T), Soen and Streek (T) series. Ant Flat and Soen soils are fine, have a calcic horizon, and occur on similar landscape positions. Dutchcanyon soils are coarse-loamy, carbonatic, and occur on similar landscape positions. Streek soils are fine and occur on similar landscape positions.
DRAINAGE AND PERMEABILITY: Well drained; high to very high surface runoff; slow permeability.
USE AND VEGETATION: Swanpeak soils are used for rangeland, wildlife habitat and building site development. The present vegetation is mainly bluebunch wheatgrass, mountain big sagebrush, mules ear, snowberry, serviceberry, Idaho fescue, basin wildrye, and small aspen groves.
DISTRIBUTION AND EXTENT: Southeastern Idaho. These soils are of small extent. MLRA 43B.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana.
SERIES ESTABLISHED: Bear Lake County, Idaho, 2008. The name is from a nearby peak.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon - The zone from the soil surface to 18 inches (A1, A2 and AB horizons).
Argillic horizon - The zone from 18 to 60 inches (Bt1, Bt2 and Bt3 horizons).
Particle size control section - The zone from 18 to 38 inches (Bt1, Bt2 and part of the Bt3 horizon).