LOCATION THEON NV
Established Series
Rev. CKS/JBF
06/2015
THEON SERIES
The Theon series consists of very shallow and shallow, well drained soils that formed in residuum and colluvium derived from volcanic rocks. Theon soils are on hills and mountains. Slopes are 4 to 75 percent. The mean annual precipitation is about 150 mm and the mean annual temperature is about 10 degrees C.
TAXONOMIC CLASS: Loamy-skeletal, mixed, superactive, mesic Lithic Haplargids
TYPICAL PEDON: Theon very gravelly sandy loam--rangeland. (Colors are for dry soil unless otherwise noted).
A--0 to 5 cm; pale brown (10YR 6/3) very gravelly sandy loam, dark yellowish brown (10YR 3/4) moist; weak medium granular structure; soft, very friable, slightly sticky and nonplastic; few fine and very fine roots; many fine and very fine interstitial pores; 40 percent gravel; moderately alkaline (pH 8.0); abrupt smooth boundary. (3 to 8 cm thick)
Bt1--5 to 15 cm; brown (7.5YR 4/4) extremely gravelly loam, dark brown (7.5YR 3/4) moist; weak fine subangular blocky structure; slightly hard, very friable, slightly sticky and slightly plastic; common medium and many fine and very fine roots; many fine and very fine interstitial pores; many faint clay films on faces of peds and lining pores; 60 percent gravel and 5 percent cobbles; moderately alkaline (pH 8.2); abrupt smooth boundary. (5 to 18 cm thick)
Bt2--15 to 28 cm; reddish brown (5YR 4/4) very gravelly clay loam, reddish brown (5YR 4/4) moist; moderate fine subangular blocky structure; hard, firm, moderately sticky and moderately plastic; common medium, fine and very fine roots; common fine and very fine tubular pores; many faint and common distinct clay films on faces of peds and lining pores; 50 percent gravel and 1 percent cobbles; moderately alkaline (pH 8.4); abrupt wavy boundary. (5 to 20 cm thick)
R--28 cm; andesite fractured in upper part with root mats and clay coats along weak fracture planes.
TYPE LOCATION: Churchill County, Nevada; in the Dead Camel Mountains about 13 miles southwest of Fallon; approximately 880 feet south and 560 feet west of the northeast corner of section 8, T. 17 N., R. 27 E.; USGS Salt Cave 7.5 minute topographic quadrangle; WSG 84 Decimal Degrees 39.3554604 latitude, -118.9713755 longitude .
RANGE IN CHARACTERISTICS:
Soil moisture: Usually dry, moist for short periods in winter and spring, dry from summer through mid-fall; typic aridic soil moisture regime.
Mean annual soil temperature: 12 to 14 degrees C.
Depth to base of argillic horizon: 20 to 36 cm.
Depth to bedrock: 20 to 36 cm to a lithic contact.
Other features: Some pedons have discontinuous thin coats of clay, silica, or silica and carbonates along weak fracture planes in the underlying bedrock.
Particle-size control section - Clay content: 25 to 35 percent.
Rock fragments: Average 35 to 60 percent, mainly gravel. Lithology of fragments is volcanic rocks such as rhyolite, andesite, or tuff.
A horizon
Value: 5 through 7 dry, 3 through 5 moist.
Chroma: 2 through 4, dry or moist.
Rock fragments: 35 to 80 percent.
Reaction: Neutral through moderately alkaline.
Effervescence: Very slightly effervescent or slightly effervescent due to recharge from calcareous dust in some pedons.
Bt horizons
Hue: 5YR through 10YR.
Value: 4 through 7 dry, 3 through 5 moist.
Chroma: 3 or 4, dry or moist.
Texture: Very gravelly clay loam, very gravelly sandy clay loam, or very gravelly loam. Subhorizons of some pedons are extremely gravelly.
Structure: Angular blocky or subangular blocky.
Consistence: Slightly hard to hard, very friable to firm, slightly sticky or moderately sticky and slightly plastic or moderately plastic.
Reaction: Neutral to strongly alkaline.
COMPETING SERIES: These are the
Downeyville,
Etinarg,
Hoot,
Mirkwood,
Tognoni,
Valleycity,
Vium, and
Waucoba series.
Downeyville,
Etinarg and
Vium soils average less 25 percent clay in the particle-size control section.
Hoot soils have mean annual soil temperature of 8 to 12 degrees C. and have an A2 horizon.
Mirkwood soils do not have abrupt boundaries between the ochric epipedon and the argillic horizon.
Tognoni soils have argillic horizons with 35 to 45 percent clay.
Valleycity soils have particle-size control section which are dominated by stones and have BCk horizons.
Waucoba soils have lithic contacts at depths of 36 to 50 cm.
GEOGRAPHIC SETTING: Theon soils are on hills and mountains. They formed in residuum and colluvium derived dominantly from volcanic rocks and some small areas of granitic rocks. Slopes are 4 to 75 percent. Elevations range from 1,220 to 2,012 meters. The climate is arid with cool, moist winters and hot, dry summers. The mean annual precipitation is 100 to 200 mm, the mean annual temperature is 9 to 12 degrees C, and the frost-free period is 100 to 130 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the
Lapon and
Singatse soils. Lapon soils are loamy-skeletal, are very shallow or shallow to duripans, and have argillic horizons. Singatse soils are loamy-skeletal, very shallow to lithic contacts, and do not have diagnostic subsurface horizons.
DRAINAGE AND SATURATED HYDRAULIC CONDUCTIVITY: Well drained; moderately high saturated hydraulic conductivity.
USE AND VEGETATION: Theon soils are used for livestock grazing and wildlife habitat. These soils have a sparse cover of shadscale, bud sagebrush, Indian ricegrass, desert needlegrass, and Nevada ephedra.
DISTRIBUTION AND EXTENT: Western Nevada. These soils are extensive with 353,000 acres of the series mapped to date. MLRAs 27 and 26.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California.
SERIES ESTABLISHED: Douglas County Area, Nevada, 1981.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - The zone from the soil surface to 5 cm (A horizon).
Argillic horizon - The zone from 5 to 28 cm (Bt1 and Bt2 horizons).
Lithic contact - The boundary at 28 cm to underlying hard bedrock (R layer).
Particle-size control section - The zone from the soil surface to 28 cm (A, Bt1, and Bt2 horizons).
ADDITIONAL DATA: A pedon of Theon is sampled for full characterization data by the Soil Survey Laboratory (SSL), Lincoln, NE, as pedon ID S08NV001002 (pedon # 08N0489).
The pedon was moved to better represent the series concept on June 2015, during an MLRA update project. Previous editors and authors include: WMA/ELS/JVC.
National Cooperative Soil Survey
U.S.A.