LOCATION SESSIONS UT+IDEstablished Series
TAXONOMIC CLASS: Fine, smectitic Xeric Argicryolls
TYPICAL PEDON: Sessions clay loam--rangeland (Colors are for air dry soil unless otherwise stated.)
A1--0 to 3 inches; dark grayish brown (10YR 4/2) clay loam, dark brown (10YR 3/3) moist; weak fine granular structure; soft, friable, slightly sticky and moderately plastic; many fine and medium roots; few very fine pores; 10 percent gravel and cobbles; slightly acid (pH 6.3); clear wavy boundary. (2 to 3 inches thick)
A2--3 to 13 inches; brown (10YR 4/3) gravelly clay loam, dark brown (10YR 3/3) moist; weak medium subangular blocky structure parting to weak medium granular; soft, friable, slightly sticky and moderately plastic; many fine and medium roots; few very fine pores; 20 percent gravel and cobbles; neutral (pH 7.1); abrupt wavy boundary. (8 to 12 inches thick)
Bt1--13 to 35 inches; brown (7.5YR 5/3) gravelly clay, brown (7.5YR 4/3) moist; moderate coarse angular blocky structure parting to strong fine and medium angular blocky; extremely hard, extremely firm, moderately sticky and very plastic; few fine roots; few fine and very fine tubular pores; thick continuous clay films and thin patchy organic stains on surfaces of peds; 15 percent gravel and cobbles; slightly acid (pH 6.2); gradual wavy boundary. (10 to 25 inches thick)
Bt2--35 to 54 inches; brown (7.5YR 5/4) cobbly clay, dark brown (7.5YR 4/3) moist; moderate coarse angular blocky structure parting to strong fine and medium angular blocky; extremely hard, extremely firm, moderately sticky and very plastic; few fine roots; few fine tubular pores; thick continuous clay films on surfaces of peds; 25 percent cobbles; slightly acid (pH 6.5); clear wavy boundary. (6 to 25 inches thick)
Bt3--54 to 61 inches; brown (7.5YR 5/4) cobbly sandy clay loam, brown (7.5YR 4/3) moist; weak fine subangular blocky structure; hard, firm, slightly sticky and moderately plastic; few fine roots; very few fine interstitial pores; thin patchy clay films on surfaces of peds; 30 percent cobbles; slightly alkaline (pH 7.4).
TYPE LOCATION: Wasatch County, Utah; 16.4 miles east from Heber Courthouse on Lake Creek Road past the forest boundary, then 1.8 miles southwest on side road; 2,800 feet north and 1,740 feet west of the southeast corner of sec. 36, T. 4 S., R. 6 E.
RANGE IN CHARACTERISTICS: The mollic epipedon is 11 to 15 inches thick. The mean annual soil temperature is 40 to 44 degrees F. and the mean summer soil temperature at a depth of 20 inches is about 58 degrees F. The soil moisture control section is dry 45 to 60 consecutive days following the summer solstice.
The A horizon has value of 3 to 5 dry, 2 or 3 moist, and chroma of 1 to 3. It has 0 to 30 percent rock fragments. It is neutral or slightly acid.
The Bt horizon has hue of 5YR or 7.5YR, value of 3 to 6 dry, 3 to 5 moist, and chroma of 3 to 6. It is clay, clay loam, gravelly clay loam or gravelly clay with more than 35 percent clay and 0 to 35 percent cobbles or gravel. Clay films are common to continuous, thin to moderately thick. Some pedons are calcareous below 40 inches.
COMPETING SERIES: Beaverdam (ID) soils have silty clay or silty clay loam in the Bt horizon, include hue of 10YR in the range, and have 0 to 10 percent rock fragments in the particle size control section.
Blackhorse (T ID) soils have Bk horizons above 40 inches, include hue of 10YR and 2.5Y in the range of the Bt horizon, and have a mean annual soil temperature of 33 to 39 degrees F.
Brinkert (CO) soils have a combined depth of the A and Bt horizons of less than 40 inches and have a mean annual precipitation that averages 12 inches.
Buckskin (ID) soils have silty clay or silty clay loam Bt horizons, have prismatic structure in the Bt horizons, don't include hue 5YR in the range, and are noncalcareous to a depth of greater than 60 inches.
Florissant (T CO) soils have a paralithic contact at a depth of 20 to 40 inches.
Gothic (CO) soils have hue of 10YR to 5Y in the Bt horizon.
Heath (CO) soils have Bk horizons above 40 inches.
Heathcoat (ID) soils have calcic horizons above 40 inches and have a mean annual precipitation of 13 to 16 inches.
Helmet (T CO) soils include hue of 10YR in the range of the Bt horizon, rock fragments average less than 15 percent in the particle size control section, and have a Udic soil moisture regime.
Jerry (CO) soils have Bk horizons above 40 inches.
Judy (CO) soils have bedrock at depths of 20 to 40 inches.
Little Horn (MT) soils have bedrock at depths of 20 to 40 inches.
Mayoworth (WY) soils have a paralithic contact at depths of 20 to 40 inches.
Owen Creek (WY) soils have a paralithic contact at depths of 20 to 40 inches.
Piltz (CO) soils have a paralithic contact at depths of 20 to 40 inches.
Sneffels (WY) soils have bedrock at depths of 20 to 40 inches.
Trout Creek (CO) soils have a paralithic contact at depths of 20 to 40 inches.
Youman (CO) soils have a combined depth of the A and B horizons of less than 50 inches and have the peak precipitation in the spring and summer.
GEOGRAPHIC SETTING: Sessions soils are on moderately steep and steep ground moraines, glacial basins and kettles of glaciated mountains at elevations of 6,300 to 10,600 feet. Slope gradients are 2 to 35 percent. The soils formed mainly in glacial till derived from mixed sedimentary parent rocks, principally sandstone, quartzite, shale but some formed in alluvium on fans in materials from gneiss and schist. The climate is humid with average annual precipitation of 22 to 35 inches, falling mostly as snow. The mean annual temperature is 35 to 44 degrees F. and the mean summer temperature is 55 to 60 degrees F. The freeze-free period is 20 to 80 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Baird Hollow, Bertag, Cluff, Ercan, Hawkins, Nordic, Roundy, Skutum, and Toone soils. These soils all have E horizons. Baird Hollow and Roundy soils have the upper boundary of the argillic horizons occurring below a 24-inch depth. Bertag and Skutum soils have mollic epipedons more than 20 inches thick. Cluff soils lack a mollic epipedon and have argillic horizons with more than 35 percent rock fragments. Ercan and Nordic soils have E horizons and the argillic horizon is more than 40 inches below the surface. Hawkins soils lack argillic horizons and cracks to the surface. Nordic soils have less than 35 percent clay in the argillic horizon and more than 35 percent rock fragments. Roundy soils have an abrupt texture change at the upper boundary of the argillic horizon. Toone soils have clay argillic horizons with more than 35 percent rock fragments.
DRAINAGE AND PERMEABILITY: Well drained; medium runoff; slow permeability.
USE AND VEGETATION: These soils are used for watershed and summer grazing by livestock and wildlife. Native plants are mountain bromegrass, oniongrass, slender wheatgrass, bearded wheatgrass, Columbia needlegrass, geranuim, horsemint, peavine, Jacobs' ladder, butterweed, bluebells, snowberry, shrubby cinquefoil, oakbrush, silver sagebrush and maple.
DISTRIBUTION AND EXTENT: High mountain park areas in northern Utah and adjoining areas of Colorado and Idaho. This series is moderately extensive.
MLRA OFFICE RESPONSIBLE: Lakewood, Colorado
SERIES ESTABLISHED: Heber Valley Area, Utah, 1972.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon - from the surface to 13 inches (A1, A2 horizon)
Argillic horizon - from 13 to 54 inches (Bt1, Bt2 horizons).
Classification: Keys to Soil Taxonomy, Eighth Edition, 1998.