LOCATION COTANT                  NV+OR

Established Series
Rev. DNC/PWB/JVC/TM
02/2016

COTANT SERIES

The Cotant series consists of shallow, well drained soils that formed in residuum and colluvium derived from tuff, rhyolite, and tuffaceous sedimentary rocks. Cotant soils are on rock pediments, hills, and mountains. Slopes are 2 to 50 percent. The mean annual precipitation is about 360 mm and the mean annual temperature is about 5.5 degrees C.

TAXONOMIC CLASS: Clayey, smectitic, frigid, shallow Aridic Argixerolls

TYPICAL PEDON: Cotant very cobbly ashy clay loam--rangeland. (Colors are for dry soil unless otherwise noted.) The soil surface is partially covered with 20 percent gravel, 30 percent cobbles, and 10 percent stones.

A--0 to 8 cm; grayish brown (10YR 5/2) very cobbly ashy clay loam, very dark grayish brown (10YR 3/2) moist; weak thick platy structure; soft, very friable, moderately sticky and moderately plastic; common fine roots; many fine interstitial and common medium vesicular pores; 30 percent cobbles and 10 percent stones; slightly alkaline (pH 7.6); clear smooth boundary. (5 to 13 cm thick)

Bt1--8 to 30 cm; grayish brown (10YR 5/2) clay, very dark grayish brown (10YR 3/2) moist; moderate medium prismatic structure; hard, very firm, very sticky and very plastic; common medium and fine roots, common fine and very fine tubular pores; many distinct clay films on faces of peds and lining pores; slightly alkaline (pH 7.4); gradual wavy boundary. (10 to 30 cm thick)

Bt2--30 to 48 cm; yellowish brown (10YR 5/4) clay, brown (10YR 4/3) moist; moderate fine and medium prismatic structure parting to moderate medium and fine angular blocky; hard, firm, very sticky and very plastic; common fine and medium roots concentrated along vertical faces of peds; common medium and fine tubular pores; 10 percent gravel; many distinct clay films on faces of peds and lining pores; slightly alkaline (pH 7.8); gradual wavy boundary. (13 to 33 cm thick)

Crt--48 to 78 cm; light yellowish brown (10YR 6/4) fractured and weathered rhyolite; dark yellowish brown (10YR 4/4) moist; few medium and fine roots along fracture planes in the bedrock; common distinct clay films lining fracture planes; clear smooth boundary. (0 to 30 cm thick)

Cr--78 cm; light gray (10YR 7/2) and yellowish brown (10YR 5/4) fractured and weathered rhyolite; few very fine roots along fracture planes in the bedrock.

TYPE LOCATION: Elko County, Nevada; about 5.5 miles east-northeast of North Fork and one mile southwest of the road crossing the West Fork of Beaver Creek; approximately 750 feet east and 1,900 feet south of the northwest corner of section 30, T. 42 N., R. 56 E.; USGS Wagon Springs 7.5 minute topographic quadrangle; latitude 41 degrees 30 minutes 15.7 seconds N and longitude 115 degrees 42 minutes 25.3 seconds W; WGS84 Decimal Degrees 41.5043611latitude, -115.7070278 longitude.

RANGE IN CHARACTERISTICS:
Soil moisture: Usually dry, moist in winter and spring, periodicly wet: non-saturated in the upper part from February through April, dry summer and fall. Aridic soil moisture regime that borders on xeric. .
Mean annual soil temperature: 5.5 to 8 degrees C.
Mollic epipedon thickness: 18 to 38 cm; includes the Bt1 horizon or both the Bt1 and Bt2 horizons.
Depth to base of argillic horizon: 30 to 50 cm.
Depth to bedrock: 30 to 50 cm to a paralithic contact. The paralithic materials below the contact are weathered rhyolite or tuff.
Reaction: Neutral or slightly alkaline.

Particle-size control section - Clay content: 40 to 60 percent.
Rock fragments: 0 to 15 percent, mainly gravel. Lithology of fragments are volcanic rocks such as tuff and rhyolite.

A horizon
Value: 5 or 6 dry, value dry is 5 after mixing the upper 18 cm of the soil.
Chroma: 2 or 3, dry or moist.
Organic matter content: 1 to 3 percent.
Volcanic glass: Volcanic glass is estimated to range from 5 to 30 percent of the 0.2 to 2 mm fraction.

Bt1 horizon
Value: 4 or 5 dry.
Chroma: 2 or 3, dry or moist.
Organic matter content: 1 or 2 percent.
Structure: Prismatic, angular blocky, or subangular blocky.
Consistence: Very friable to firm, moist; moderately sticky or very sticky and moderately plastic or very plastic, wet.

Bt2 horizon
Value: 4 through 6 dry, 3 through 5 moist.
Chroma: 2 through 4, dry or moist.
Organic matter content: 0 to 2 percent.
Structure: Prismatic, angular blocky, or subangular blocky.
Consistence: Very friable to firm, moist; moderately sticky or very sticky and moderately plastic or very plastic, wet.
Other features: Some pedons have thin subhorizons with up to 25 percent rock fragments.

COMPETING SERIES: This is the Ichbod series.

Ichbod soils have 15 to 35 percent rock fragments in the particle-size control section and have upper subhorizons of the argillic horizon with 25 to 35 percent clay.

GEOGRAPHIC SETTING: Cotant soils are on rock pediments, hills, and mountains. These soils formed in residuum and colluvium derived from tuff, rhyolite, and tuffaceous sedimentary rocks. Slopes are 2 to 50 percent. Elevations range from 1,590 to 2,445 meters. The climate is semiarid with cool, moist winters and warm, dry summers. The mean annual precipitation is 230 to 400 mm, the mean annual temperature is 4 to 8 degrees C, and the frost-free period is 70 to 100 days.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the McIvey and Shively soils. McIvey soils are clayey-skeletal, very deep, have mollic epipedons and argillic horizons, and occur on adjacent fan remnants. Shively soils are coarse-loamy, deep to paralithic contacts, and have thick mollic epipedons.

DRAINAGE AND SATURATED HYDRAULIC CONDUCTIVITY: Well drained; very high surface runoff; moderately low saturated hydraulic conductivity.

USE AND VEGETATION: Cotant soils are used for rangeland and wildlife habitat. The vegetation is mainly low sagebrush, Douglas rabbitbrush, cheatgrass, bottlebrush squirreltail, and Sandberg's bluegrass.

DISTRIBUTION AND EXTENT: Northern Nevada and southeastern Oregon. These soils are moderately extensive. MLRAs 10, 23, and 25.

MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California.

SERIES ESTABLISHED: Elko County (Central Part), Nevada, 1986.

REMARKS: Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon - The zone from the soil surface to 30 cm (A and Bt1 horizons).
Argillic horizon - The zone from 8 to 48 cm (Bt1 and Bt2 horizons).
Ashy textures - Volcanic glass is estimated to be 5 to 30 percent of the 0.02 to 2 mm fraction in the zone from 0 to 8 cm (A horizons).
Paralithic contact - The boundary at 48 cm to underlying soft, weathered bedrock (Crt layer).
Particle-size control section - The zone from 8 to 48 cm (Bt1 and Bt2 horizons).

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National Cooperative Soil Survey
U.S.A.