LOCATION TOPHAT IDEstablished Series
TAXONOMIC CLASS: Fine, mixed, superactive Pachic Argicryolls
TYPICAL PEDON: Tophat cobbly loam, on a 47 percent slope with east aspect at 6000 feet elevation, in a mountain big sagebrush/ bluebunch wheatgrass community, rangeland. (Colors are for dry soil unless otherwise noted.)
A--0 to 7 inches; very dark grayish brown (10YR 3/2) cobbly loam, very dark brown (10YR 2/2) moist; moderate medium granular structure parting to weak very fine granular; slightly hard, friable, slightly sticky and slightly plastic; many very fine and fine roots, common medium roots; many very fine and common fine irregular pores; 10 percent pebbles, 10 percent cobbles; neutral (pH 7.0); abrupt smooth boundary. (4 to 8 inches thick)
AB--7 to 17 inches; reddish gray (5YR 5/2) cobbly clay loam, dark reddish brown (5YR 3/2) moist; moderate medium subangular blocky structure parting to moderate medium granular; hard, firm, moderately sticky and moderately plastic; common very fine, fine and medium roots; many very fine tubular pores, common fine irregular pores; few faint dark reddish brown (5YR 3/2) moist clay films on faces of peds; 10 percent pebbles, 15 percent cobbles; slightly acid (pH 6.5); clear smooth boundary. (0 to 12 inches thick)
Bt1--17 to 28 inches; reddish brown (5YR 5/3) cobbly clay loam, dark reddish brown (5YR 3/3) moist; strong medium subangular blocky structure parting to strong very fine subangular blocky; hard, firm, moderately sticky and very plastic; few very fine, fine and medium roots; common very fine tubular and few fine tubular pores; many faint dark reddish brown (5YR 3/3) moist clay films on faces of peds; few distinct dark reddish brown (5YR 3/3) moist clay films lining pores; 10 percent pebbles, 15 percent cobbles; slightly acid (pH 6.5); clear smooth boundary. (5 to 15 inches thick)
Bt2--28 to 34 inches; reddish brown (5YR 5/3) cobbly clay loam, dark reddish brown (5YR 3/3) moist; strong medium subangular blocky structure; very hard, firm, moderately sticky and very plastic; few very fine, fine and medium roots; common very fine and few fine tubular pores; common distinct dark reddish brown (5YR 3/3) moist clay films on faces of peds and lining pores; 10 percent pebbles, 20 percent cobbles; slightly acid (pH 6.5); clear smooth boundary. (5 to 15 inches thick)
Bt3--34 to 45 inches; reddish brown (5YR 5/3) cobbly silty clay loam, weak red (2.5YR 4/2) moist; moderate coarse prismatic structure parting to moderate coarse subangular blocky; very hard, very firm, moderately sticky and very plastic; few very fine and medium roots; common very fine tubular pores; common distinct weak red (2.5YR 4/2) moist clay films on faces of peds and lining pores; 10 percent pebbles, 20 percent cobbles; slightly acid (pH 6.5); gradual smooth boundary. (5 to 15 inches thick)
Bt4-- 45 to 60 inches; reddish brown (5YR 5/3) very cobbly silty clay loam, weak red (2.5YR 4/2) moist; moderate very coarse prismatic structure parting to moderate very coarse subangular blocky; very hard, very firm, moderately sticky and very plastic; few very fine and medium roots; common very fine tubular pores; common distinct weak red (2.5YR 4/2) moist clay films on faces of peds and lining pores; 5 percent pebbles, 20 percent cobbles, 10 percent stones; slightly acid (pH 6.5).
TYPE LOCATION: Bonneville County, Idaho, about 12.5 miles south and 4.5 miles east of Swan Valley; about 1200 feet east and 1500 feet south of the northwest corner of section 1, T. 2 S., R 44 E.; Latitude- 43 degrees North, 16 minutes, 34 seconds; Longitude - 111 degrees West, 14 minutes, 50 seconds.
RANGE IN CHARACTERISTICS:
Mean annual soil temperature - 38 to 42 degrees F.
Mean summer soil temperature - 50 to 54 degrees F.
Moisture control section - between 4 and 12 inches. The soil is dry for 30 to 45 consecutive days in the four months following the summer solstice.
Mollic epipedon thickness - 16 to 40 inches.
Depth to argillic horizon - 4 to 20 inches.
Clay content in particle-size control section, weighted average - 35 to 50 percent.
Rock fragments in particle-size control section, weighted average - 0 to 35 percent.
A horizon - Hue: 7.5YR or 10YR
Value: 3, 4 or 5 dry, 2 or 3 moist
Chroma: 2 or 3 dry or moist
Clay content: 20 to 27 percent
Rock fragments: 15 to 35 percent
Pebbles: 0 to 15 percent
Cobbles: 10 to 20 percent
Stones: 0 to 5 percent
Reaction: pH 6.6 to 7.3
AB horizon - Hue: 2.5YR, 5YR, 7.5YR or 10YR
Value: 4 or 5 dry, 2 or 3 moist
Chroma: 2 or 3
Texture: silty clay loam or clay loam
Clay content: 27 to 40 percent
Rock fragment content: 0 to 35 percent
Pebbles: 0 to 15 percent
Cobbles: 0 to 20 percent
Stones: 0 to 5 percent
Reaction: pH 6.1 to 7.3
Bt1 and Bt2 horizons - Hue: 2.5YR, 5YR, 7.5YR or 10YR
Value: 5 or 6 dry; 3, 4 or 5 moist
Chroma: 2, 3 or 4
Texture: clay, silty clay loam or clay loam
Clay content: 35 to 50 percent
Rock fragments: 0 to 35 percent
Pebbles: 0 to 15 percent
Cobbles: 0 to 20 percent
Stones: 0 to 5 percent
Reaction: pH 6.1 to 7.3
Bt3 and Bt4 horizons - Hue: 2.5YR, 5YR, 7.5YR or 10YR
Value: 4, 5, 6 or 7 dry; 4, 5 or 6 moist
Chroma: 2, 3 or 4
Texture: silty clay loam or clay loam
Clay content: 27 to 40 percent
Rock fragments: 15 to 60 percent
Pebbles: 0 to 15 percent
Cobbles: 10 to 30 percent
Stones: 0 to 20 percent
Reaction: pH 5.6 to 7.3
COMPETING SERIES:
Cratermo (ID) - are 20 to 40 inches to a lithic contact.
Hammersley (OR) - are 40 to 60 inches to a paralithic contact.
GEOGRAPHIC SETTING:
Landform - foothills and mountains.
Elevation - 5600 to 8000 feet.
Slope - 15 to 50 percent.
Parent material - local alluvium, colluvium or residuum derived from mixed sources.
Climate - winters are moist and cool, summers are warm and dry. A winter snowpack of 2 to 4 feet in depth and lasting through April is common.
Mean annual temperature - 36 to 40 degrees F.
Mean annual precipitation - 20 to 28 inches.
Frost free period - 30 to 70 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Etnass, Jumpstart, Nearl, Quirt and Sedgway series. Etnass soils are on nearby ridges, summits and sideslopes. They formed in residuum from shale, have intersecting slickensides and cracks, and are 10 to 40 inches deep to carbonates. Jumpstart soils are on nearby sideslopes. They have a forest litter horizon and lack a mollic epipedon. Nearl soils are on nearby basins. They have a forest litter horizon, lack an argillic horizon, and have a mollic epipedon less than 16 inches thick. Quirt soils are on nearby sideslopes. They formed in residuum from shale, have a mollic epipedon less that 16 inches thick, and are 15 to 30 inches deep to carbonates. Sedgway soils are on nearby ridges, summits and sideslopes. They average less than 35 percent clay in the particle-size control section and have a mollic epipedon less than 16 inches thick.
DRAINAGE AND PERMEABILITY: Well drained, medium to rapid runoff, slow permeability.
USE AND VEGETATION: Tophat soils are used for livestock grazing, recreation and wildlife habitat. These soils commonly support communities that have a shrub layer of mountain big sagebrush, spike big sagebrush or subalpine big sagebrush, with an herbaceous layer dominated by California brome, slender wheatgrass or bluebunch wheatgrass.
DISTRIBUTION AND EXTENT: Southeastern Idaho. They are of moderate extent.
MLRA OFFICE 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 34 inches (the A, AB, Bt1 and Bt2 horizons)
Argillic horizon - the zone from 17 to 60 inches (the Bt1, Bt2, Bt3 and Bt4 horizons)
Particle-size control section - the zone from 17 to 37 inches (the Bt1, Bt2 and part of the Bt3 horizons)
Moisture regime - udic
ADDITIONAL DATA: Primary Characterization Data (06/27/89) NSSL, Lincoln, NE. Client-Assigned Laboratory Number S88ID-019-005; Project File numbers 88P 148; Laboratory-Assigned Numbers: Pedon 88P 836, Samples 88P4373-4377.