LOCATION ETNASS IDEstablished Series
TAXONOMIC CLASS: Fine, smectitic Typic Humicryerts
TYPICAL PEDON: Etnass clay loam, on a 12 percent slope with south aspect at 5960 feet elevation, in a tall forb community. When described on August 20, 1996 the soil was moist below a depth of 11 inches (colors are for dry soil unless otherwise noted).
A--0 to 5 inches; grayish brown (2.5Y 5/2) clay loam, very dark grayish brown (10YR 3/2) moist; weak coarse subangular blocky structure parting to strong medium and coarse granular; hard, firm, sticky and plastic; many very fine and common fine roots, few medium and coarse roots; many medium irregular and common coarse irregular pores, few very fine and medium tubular pores; few 1 inch wide vertical desiccation cracks; trace pebbles; neutral (pH 7.3); clear smooth boundary. (4 to 12 inches thick)
Bt--5 to 11 inches; grayish brown (2.5Y 5/2) silty clay, very dark grayish brown (10YR 3/2) moist; moderate very coarse subangular blocky structure parting to strong coarse subangular blocky; very hard, very firm, sticky and very plastic; common very fine roots, few medium and coarse roots; few very fine, fine and medium tubular pores; few 1/2 to 1 inch wide vertical desiccation cracks; common distinct very dark grayish brown (10YR 3/2) moist pressure faces on ped faces; trace pebbles; neutral (pH 7.2); clear wavy boundary. (6 to 28 inches thick)
Btkss1--11 to 36 inches; light brownish gray (2.5Y 6/2) silty clay, grayish brown (2.5Y 5/2) moist; strong very coarse prismatic structure parting to strong coarse angular blocky; very hard, very firm, sticky and very plastic; few very fine, medium and coarse roots; few very fine tubular pores; few distinct intersecting slickensides; very few 3/8 to 5/8 inch wide vertical desiccation cracks; many distinct grayish brown (2.5Y 5/2) moist continuous pressure faces on ped faces; few distinct dark gray (10YR 4/1) moist discontinuous clay films on faces of peds; trace pebbles; common fine (1/8 to 1/4 inch) masses and few medium (2/8 to 5/8 inch) discontinuous bands of lime; strongly effervescent; slightly alkaline (pH 7.8); gradual wavy boundary. (5 to 30 inches thick)
Btkss2--36 to 45 inches; light brownish gray (2.5Y 6/2) silty clay, grayish brown (2.5Y 5/2) moist; strong very coarse prismatic structure parting to strong coarse angular blocky; very hard, very firm, sticky and very plastic; few very fine and medium roots; few very fine tubular pores; many distinct intersecting slickensides; very few 3/8 to 5/8 inch wide vertical desiccation cracks; few fine prominent brown (10YR 5/3) moist soft Fe/Mn accumulations along root channels; common distinct brown (7.5YR 5/3) moist continuous clay films or pressure faces along slickensides and on faces of peds; few distinct dark gray (10YR 4/1) moist discontinuous clay films on faces of peds; trace pebbles; common fine (1/8 to 1/4 inch) and medium (1/4 to 5/8 inch) masses and few fine (1/8 to 1/4 inch) discontinuous bands of lime; violently effervescent; moderately alkaline (pH 8.0); clear wavy boundary. (5 to 15 inches thick)
Bkss--45 to 65 inches; light olive gray (5Y 6/2) clay, olive gray (5Y 5/2) moist; moderate very coarse prismatic structure parting to moderate coarse angular blocky; very hard, very firm, sticky and very plastic; few very fine roots; few very fine tubular pores; many distinct intersecting slickensides; very few 1/4 to 1/2 inch wide vertical desiccation cracks; few distinct brown (7.5YR 5/3) moist discontinuous streaks in matrix and clay films or pressure faces along slickensides; trace pebbles; common coarse (3/4 to 3 inch) discontinuous bands and few medium (1/4 to 3/8 inch) masses of lime; violently effervescent; moderately alkaline (pH 8.0).
TYPE LOCATION: Bonneville County, Idaho, about 26 miles southeast of Swan Valley; about 550 feet east and 2850 feet south of the northwest corner of section 27, T. 3 S., R. 46 E.; Latitude - 43 degrees North, 07 minutes, 38 seconds; Longitude - 111 degrees West, 03 minutes, 20 seconds.
RANGE IN CHARACTERISTICS:
Mean annual soil temperature - 39 to 44 degrees F.
Mean summer soil temperature - 51 to 56 degrees F.
Moisture control section - between 4 and 12 inches. The soil is dry throughout the moisture control section for 30 to 45 consecutive days during the four months following the summer solstice.
Mollic epipedon thickness - 4 to 40 inches.
Depth to argillic horizon - 4 to 12 inches.
Depth to carbonates - 10 to 40 inches.
Depth to Bkss horizon - 20 to greater than 60 inches.
Extra-structural cracks: very few to few subsurface-initiated reversible cracks.
Organic carbon: 10 to 15 kg/m2 in the upper 20 inches of the profile.
A horizon - Hue: 10YR or 2.5Y
Value: 4 or 5 dry, 2 or 3 moist
Chroma: 2 or 3
Clay content: 30 to 40 percent
Rock fragment content: 0 to 5 percent pebbles
Reaction: pH 6.6 to 7.3
Bt horizon - Hue: 5YR, 7.5YR, 10YR or 2.5Y
Value: 5 or 6 dry; 3, 4 or 5 moist
Chroma: 2 or 3
Texture: clay or silty clay
Clay content: 40 to 60 percent
Rock fragment content: 0 to 5 percent pebbles
Reaction: pH 6.6 to 7.3
Btkss horizons - Hue: 5YR, 7.5YR, 10YR or 2.5Y
Value: 5 or 6 dry; 4, 5 or 6 moist
Chroma: 2 or 3
Texture: clay or silty clay
Clay content: 40 to 60 percent
Rock fragment content: 0 to 5 percent pebbles
Redoximorphic features: Kind - soft Fe accumulations, soft Fe/Mn accumulations, or Fe/Mn depletions
Abundance - absent to common
Size - fine to medium
Contrast - distinct or prominent
Calcium carbonate equivalent: 5 to 40 percent in the less than 2 mm size fraction
Effervescence: slightly to violently
Reaction: pH 7.4 to 8.4
Bkss horizon - Hue: 5YR, 7.5YR, 10YR, 2.5Y or 5Y
Value: 5 or 6 dry; 4, 5 or 6 moist
Chroma: 2, 3 or 4
Texture: clay loam, clay or silty clay
Clay content: 35 to 50 percent
Rock fragment content: 0 to 20 percent pebbles
Soft shale fragments: 0 to 20 percent
Calcium carbonate equivalent: 15 to 40 percent in the less than 2 mm size fraction
Effervescence: strongly or violently
Reaction: pH 7.9 to 8.4
COMPETING SERIES: There are no competing series.
GEOGRAPHIC SETTING:
Landform - foothills.
Elevation - 5700 to 6700 feet.
Slope- 4 to 20 percent.
Parent material - residuum derived from shale.
Climate - Precipitation is evenly distributed throughout the year. A winter snowpack of 3 to 6 feet in depth and lasting through mid May is common.
Mean annual temperature - 37 to 42 degrees F.
Mean annual precipitation - 18 to 25 inches.
Frost free period - 30 to 70 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Huckridge, Nearl, Sedgway and Tophat series. Huckridge soils are on nearby summits. They formed in local alluvium derived from loess, lack a mollic epipedon and average 18 to 27 percent clay in the particle-size control section. Nearl soils are in nearby basins. They have a forest litter layer and lack an argillic horizon. Sedgway soils are on nearby summits and sideslopes. They average less than 35 percent clay in the particle-size control section and do not have cracks or slickensides. Tophat soils are on nearby sideslopes. They formed in local alluvium or colluvium derived from mixed sources, lack desiccation cracks, and lack intersecting slickensides within 40 inches of the soil surface.
DRAINAGE AND PERMEABILITY: Moderately well drained, slow to medium runoff, slow permeability.
USE AND VEGETATION: Etnass soils are used for livestock grazing, recreation and wildlife habitat. These soils commonly support herbaceous communities dominated by mulesears wyethia.
DISTRIBUTION AND EXTENT: Southeastern Idaho. They are of small extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana.
SERIES ESTABLISHED: Targhee National Forest, Bonneville County, Idaho, 1997.
REMARKS:
Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon - the zone from the mineral soil surface to 11 inches (A and Bt horizons)
Argillic horizon - the zone from 5 to 45 inches (Bt, Btkss1 and Btkss2 horizons)
Calcic horizon - the zone from 11 to 65 inches (Btkss1, Btkss2 and Bkss horizons)
Particle-size control section - the zone from 10 to 40 inches ( part of the Bt, Btkss1, part of the Btkss2 horizon)
Cracks- the zone from 0 to 65 inches (A, Bt, Btkss1, Btkss2 and Bkss horizons)
Intersecting slickensides - the zone from 11 to 65 inches (Btkss1, Btkss2 and Bkss horizons)
Moisture regime - udic