LOCATION FOSSILBUTTE WY
Tentative Series
Rev. JGM-RJS
10/2013
FOSSILBUTTE SERIES
The Fossilbutte series consists of very deep, well drained soils that formed in slope alluvium derived from interbedded sandstone and shale. These soils occur on ridges, mesas and buttes. Slopes are 1 to 20 percent. Mean annual precipitation is about 430 mm and mean annual air temperature is about 3.5 degrees C.
TAXONOMIC CLASS: Fine, smectitic Vertic Haplocryalfs
TYPICAL PEDON: Fossilbutte clay loam, in rangeland (colors are for dry soil unless otherwise noted).
A--0 to 7 cm; brown (7.5YR 4/2) clay loam, dark brown (7.5YR 3/2) moist; moderate medium granular structure; slightly hard, friable, slightly sticky and slightly plastic; common very fine and fine roots throughout; common very fine and fine dendritic tubular pores; very slightly effervescent; slightly alkaline (pH 7.6); clear smooth boundary. (5 to 15 cm thick)
Bt1--7 to 15 cm; brown (7.5YR 4/2) clay loam, dark brown (7.5YR 3/2) moist; moderate medium subangular blocky structure; slightly hard, friable, moderately sticky and moderately plastic; common very fine and fine, and few medium roots throughout; common very fine and fine dendritic tubular pores; 10 percent faint clay films on all faces of peds; finely disseminated calcium carbonate; slightly effervescent; slightly alkaline (pH 7.4); clear smooth boundary. (0 to 15 cm thick)
Bt2--15 to 79 cm; brown (7.5YR 5/3) clay, brown (7.5YR 4/3) moist; strong medium prismatic structure parting to strong medium angular; hard, firm, moderately sticky and very plastic; few fine roots throughout and few medium roots between peds; few very fine dendritic tubular pores; 70 percent distinct clay films on all faces of peds; 5 percent angular sedimentary gravel; finely disseminated calcium carbonate; slightly effervescent; slightly alkaline (pH 7.4); gradual smooth boundary. (45 to 85 cm thick)
Btk1--79 to 99 cm; reddish brown (5YR 5/3) clay, reddish brown (5YR 4/3) moist; moderate medium angular blocky structure; hard, firm, moderately sticky and very plastic; few very fine roots throughout; few very fine dendritic tubular pores; 45 percent distinct clay films on all faces of peds; 10 percent angular sedimentary gravel; 1 percent faint irregular carbonate masses on faces of peds and finely disseminated calcium carbonate; strongly effervescent; moderately alkaline (pH 8.0); gradual smooth boundary. (8 to 30 cm thick)
Btk2--99 to 200 cm; reddish brown (5YR 5/3) clay, reddish brown (5YR 4/3) moist; moderate medium angular blocky structure; hard, firm, moderately sticky and very plastic; few very fine dendritic tubular pores; 20 percent faint clay films on vertical faces of peds; 5 percent angular sedimentary gravel; 7 percent prominent medium irregular carbonates masses in the matrix and finely disseminated calcium carbonate; strongly effervescent; moderately alkaline (pH 8.0).
TYPE LOCATION: Lincoln County, Wyoming; 41 degrees 53 minutes 47.65 seconds north latitude and 110 degrees 46 minutes 18.84 seconds west longitude; NAD83, UTM 518921 meters E, 4638318 meters N, zone 12.
RANGE IN CHARACTERISTICS:
Mean annual soil temperature - 3.5 to 6.0 degrees C.
Depth to top of argillic horizon - 10 to 25 cm
Depth to secondary calcium carbonate accumulation - 65 to 100 cm
Note: The Bt1 is not part of the argillic horizon.
A horizon
Hue: 5YR to 10YR; dry or moist
Value: 4 to 6 dry; 3 or 4 moist
Chroma: 2 or 3; dry or moist
Clay content: 27 to 35 percent
Rock fragments: 0 to 5 percent gravel
Reaction: pH 7.0 to 7.6
Bt1 horizon
Hue: 5YR to 10YR; dry or moist
Value: 4 to 6 dry, 3 or 4 moist
Chroma: 2 or 3; dry or moist
Clay content: 30 to 36 percent
Rock fragments: 0 to 5 percent gravel
Calcium carbonate equivalent: 0 to 3 percent
Reaction: pH 7.2 to 7.8
Bt2 horizon
Hue: 5YR to 10YR; dry or moist
Value: 5 or 6 dry, 4 or 5 moist
Chroma: 2 to 4; dry or moist
Texture: clay, clay loam
Clay content: 35 to 50 percent
Rock fragments: 0 to 20 percent gravel
Calcium carbonate equivalent: 0 to 3 percent
Reaction: pH 7.2 to 7.8
Btk1, Btk2 horizon(s)
Hue: 5YR to 10YR; dry or moist
Value: 5 or 6 dry, 4 or 5 moist
Chroma: 2 to 4; dry or moist
Texture: clay, clay loam
Clay content: 35 to 50 percent
Rock fragments: 0 to 25 percent gravel
Calcium carbonate equivalent: 5 to 15 percent
Reaction: pH 7.9 to 8.4
COMPETING SERIES:
Bridgerton (WY) - have an udic moisture regime
Doolittle (MT) - are moderately deep to a paralithic contact
Goldhill (ID) - have a xeric moisture regime
Harkness (ID) - have an udic moisture regime
Herd (UT) - do not have secondary calcium carbonate accumulation
Sledrunner (WY) - have secondary calcium carbonate accumulation throughout the argillic horizon
GEOGRAPHIC SETTING:
Landform - ridges, mesas and buttes
Elevation - 2,250 to 2,450 meters
Slope - 1 to 20 percent
Parent Material - slope alluvium derived from interbedded sandstone and shale
Climate - long, cold winters; short, cool summers
Mean annual precipitation - 380 to 480 mm with peak periods of precipitation occurring from March to June
Mean annual air temperature - 3.0 to 5.0 degrees C.
Frost-free period - 30 to 60 days
GEOGRAPHICALLY ASSOCIATED SOILS: None listed.
DRAINAGE AND PERMEABILITY: Well drained; slow permeability.
USE AND VEGETATION: Fossilbutte soils are primarily used for rangeland and wildlife habitat. The potential native vegetation may include early sage, Hood's phlox, and thickspike wheatgrass.
DISTRIBUTION AND EXTENT: Fossilbutte soils are of small extent in southwestern Wyoming. MLRA - 46.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana.
SERIES PROPOSED: Lincoln County, Wyoming, 2013. The series name is coined.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - 0 to 7 cm (A horizon)
Argillic horizon - 15 to 200 cm (Bt2, Btk1, Btk2 horizons)
Secondary calcium carbonate accumulation - 79 to 200 cm (Btk1, Btk2 horizons)
Particle-size control section - 15 to 65 cm (part of Bt2 horizon)
Fossilbutte soils have a cryic temperature regime and an ustic moisture regime.
National Cooperative Soil Survey
U.S.A.