LOCATION FOURMILE           CO+WY+MT

FOURMILE SERIES

TAXONOMIC CLASS: Loamy-skeletal, mixed, superactive Ustic Argicryolls

TYPICAL PEDON: Fourmile gravelly coarse sandy loam, grassland. (Colors are for dry soil unless otherwise noted).

A1--0 to 5 inches; dark grayish brown (10YR 4/2) gravelly coarse sandy loam, very dark brown (10YR 2/2) moist; strong fine granular structure; soft, very friable, nonsticky, nonplastic; 15 percent fine and very fine angular gravel; neutral (pH 6.6); clear smooth boundary.

A2--5 to 9 inches; dark grayish brown (10YR 4/2) very gravelly coarse sandy loam, very dark brown (10YR 2/2) moist; weak coarse subangular blocky structure parting to medium granular; slightly hard, very friable, nonsticky, nonplastic; primary peds are hard; thin glossy patches on some sand grains; 60 percent fine and very fine angular gravel; neutral (pH 6.6); clear smooth boundary. (combined thickness of the A horizons: 7 to 18 inches thick)

Bt--9 to 20 inches; brown (7.5YR 5/3) very gravelly sandy clay loam, brown (7.5YR 4/3) moist; moderate coarse prismatic structure parting to coarse subangular blocky; slightly hard, very friable, slightly sticky, slightly plastic; peds are extremely hard; thin wax like patches on faces of peds and wax like coatings and fillings on the inside of root channels and pores; wax-like bridges between sand grains and wax like coatings on sand grains; 60 percent fine and very fine angular gravel; neutral (pH 6.6); clear smooth boundary. (6 to 41 inches thick)

BC--20 to 24 inches; brown (7.5YR 5/3) very gravelly coarse sandy loam, brown (7.5YR 4/3) moist; weak coarse subangular blocky structure; slightly hard, very friable, nonsticky, nonplastic; peds are extremely hard; few thin glossy coats on some faces of peds and discontinuous glossy coatings in some root channels; 60 percent fine and very fine angular gravel; neutral (pH 6.8); gradual wavy boundary. (3 to 15 inches thick)

2C--24 to 60 inches; very gravelly coarse sand or loamy sand; 55 percent gravel; neutral (pH 6.8).

TYPE LOCATION: Teller County, Colorado; approximately 2.5 miles south of the village of Florissant and about 0.2 mile north of the road junction in the SE1/4 sec. 24, T. 13 S., R. 71 W.

RANGE IN CHARACTERISTICS:
Mean annual soil temperature: 36 to 44 degrees F.
Mean summer soil temperature: 50 to 58 degrees F.
Soil moisture: ustic moisture regime
Depth to the coarse textured 2C horizon: 20 to 40 inches, in some pedons is deeper than 40 inches if it immediately underlies a solum thicker than 40 inches
Depth to the base of the argillic horizon: 15 to 50 inches

Sand fraction: 15 to about 90 percent, content of medium and coarser angular sand have a large proportion of flat bearing surfaces between sand grains

A horizon:
Hue: 2.5Y through 7.5YR
Value: 3 through 5, 2 or 3 moist
Chroma: 1 through 3
Rock fragment content: 35 to 75 percent
Reaction: moderately acid through slightly alkaline

Bt horizon:
Hue: 2.5Y through 7.5YR
Value: 5 or 6, 4 through 6 moist
Chroma: 2 through 6
Texture: gravelly or very gravelly, sandy clay loam and sandy loam
Clay: 18 to 35 percent
Silt: 5 to 40 percent
Sand: 40 to 75 percent with more than 35 percent being fine or coarser sand, a high proportion of medium and coarse sand
Rock fragment content: 35 to 75 percent
Reaction: moderately acid through slightly alkaline

2C horizon:
Rock fragment content: 35 to 90 percent, (mainly 1/8 to 1 inch in diameter with up to 10 percent cobble)

COMPETING SERIES: Blaine, Bowen, Geertsen, Nathale, Nathrop, Woodhall : have lithic contacts within 60 inches of the surface
Hodden, Libeg : have less than 35 percent fine sand or coarser sand in the argillic horizon
Hoodle, Lagarita, Maciver, Teeler : have calcic horizons
Fornor, Quander, Ratiopeak, Spanpeak : do not have lithologic discontinuity with sandy-skeletal materials
Parkview : has a paralithic contact between 20 and 40 inches below the surface
Norriston : less than 18 percent clay in the argillic horizon

GEOGRAPHIC SETTING: The Fourmile soils are on remnant terraces, terraces, alluvial fans, outwash plains, and eskers. Slopes range from 2 to 25 percent. The soils formed in moderately thin, noncalcareous, moderately coarse to moderately fine textured materials derived principally from granite. At the type location the mean annual precipitation is about 18 inches with peak periods of precipitation in the spring and early summer. Mean annual temperature is 40 degrees F., mean summer temperature is 57 degrees F. Elevation is 8000 to 8800 feet. Elevation in Montana is 6,200 to 7,000 feet. Frost-free period in Montana is 30 to 70 days.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Handran and Norriston soils. Handran soils lack an argillic horizon and are gravelly sandy loam to depths of more than 40 inches. Norriston soils have coarse textured 2C horizons at depths of less than 20 inches and have thin solums less than 15 inches thick.

DRAINAGE AND PERMEABILITY: Well to somewhat excessively drained; medium to low runoff; slow through moderate permeability (moderately high Ksat).

USE AND VEGETATION: Used as grazing land, for recreation, or for limited timber production. Native vegetation is mainly scattered ponderosa pine, Arizona fescue, Parry oatgrass, mountain muhly, slimstem muhly, blue grama, fringed sagebrush, rabbitbrush, native bluegrass, prairie junegrass, and needlegrass.

DISTRIBUTION AND EXTENT: Central Colorado and Wyoming. The series is of moderate extent.

MLRA OFFICE RESPONSIBLE: Lakewood, Colorado

SERIES ESTABLISHED: Bighorn National Forest, Wyoming 1982.