LOCATION THWOOP                  NV

Established Series
Rev. RWD/TSB/RLB/JBF
12/2019

THWOOP SERIES

The Thwoop series consists of moderately deep, well drained soils that formed in residuum and colluvium derived from rhyolite and shallow intrusive rocks. The Thwoop soils are on fan piedmont remnants with a rock core, hills and mountains. Slopes are 4 to 15 percent. The mean annual precipitation is about 280 mm and the mean annual temperature is about 7 degrees C.

TAXONOMIC CLASS: Clayey-skeletal, smectitic, frigid Argiduridic Durixerolls

TYPICAL PEDON: Thwoop gravelly silt loam--rangeland. (Colors are for dry soils unless otherwise noted.)

A1--0 to 10 cm; brown (10YR 5/3) gravelly silt loam, very dark grayish brown (10YR 3/2) moist; moderate fine and medium subangular blocky structure; soft, very friable, slightly sticky and slightly plastic; many very fine and fine roots; common very fine and fine tubular pores; 15 percent gravel; neutral (pH 7.2); clear smooth boundary. (8 to 15 cm thick)

A2--10 to 25 cm; brown (10YR 5/3) silt loam, very dark grayish brown (10YR 3/2) moist; weak fine and medium subangular blocky structure; soft, very friable, slightly sticky and moderately plastic; common medium, few very fine and fine roots; many very fine and fine tubular pores; 5 percent gravel; neutral (pH 7.2); clear smooth boundary. (10 to 20 cm thick)

Bt--25 to 41 cm; yellowish brown (10YR 5/4) very gravelly clay, dark yellowish brown (10YR 4/4); moderate fine and medium subangular blocky structure; slightly hard, friable, moderately sticky and moderately plastic; common medium, few very fine and fine roots; many very fine, fine and few medium tubular pores; common distinct clay films on ped faces and lining pores; 10 percent cobbles, 30 percent gravel; neutral (pH 7.2); clear wavy boundary. (13 to 23 cm thick)

Btk--41 to 64 cm; dark yellowish brown (10YR 4/6) very gravelly clay, dark yellowish brown (10YR 4/4) moist; strong fine and medium subangular blocky structure; moderately hard, firm, moderately sticky and very plastic; common medium roots; common fine and medium tubular pores; many prominent clay films on ped faces and lining pores; common fine soft carbonatic masses and filaments, 10 percent cobbles, 40 percent gravel, noneffervescent matrix, strongly effervescent in spots; slightly alkaline (pH 7.4); abrupt wavy boundary. (18 to 30 cm thick)

Bqkm--64 to 69 cm; indurated duripan with 1 to 2 mm laminar cap; extremely hard, very firm; violently effervescent; abrupt wavy boundary. (3 to 10 cm thick)

R--69 cm; hard, fractured rhyolite.

TYPE LOCATION: Elko County, Nevada; approximately 8 miles south - southwest of Midas, Nevada, about 2,820 feet west and 2,130 feet north of the southeast corner of section 12, T. 37 N., R. 46 E.; USGS Sixmile Hill 7.5 minute topographic quadrangle; latitude 41 degrees 5 minutes 50 seconds N and longitude 116 degrees 50 minutes 43 seconds; WGS84 Decimal Degrees 41.0969444 latitude, -116.8452778 longitude..

RANGE IN CHARACTERISTICS:
Soil moisture: Moist in winter and spring, dry July through October; aridic soil moisture regime bordering on xeric.
Mean annual soil temperature: 6 to 8 degrees C.
Mollic epipedon thickness: 18 to 36 cm.
Depth to duripan: 50 to 76 cm.
Depth to bedrock: 53 to 81 cm.
Soil reaction: Neutral or slightly alkaline.

Particle-size control section - Clay content: 35 to 45 percent.
Rock fragments: 35 to 60 percent, mainly gravel.

A horizon
Value: 4 or 5 dry.
Chroma: 2 or 3.

Bt and Btk horizons
Value: 4 or 5 dry, 3 or 4 moist.
Chroma: 4 through 6.
Texture: Very gravelly clay or very gravelly clay loam.
Carbonates: Noneffervescent or slightly effervescent matrix with strong effervescence in spots, generally increasing with depth.

COMPETING SERIES: There are no other soils in this family.

GEOGRAPHIC SETTING: Thwoop soils are on fan piedmont remnants with a rock core, hills and mountains. These soils formed in residuum and colluvium derived from rhyolite and shallow intrusive rocks. Slopes are 4 to 15 percent. Elevations are 1,555 to 1,830 meters. The climate is cool semiarid, with warm, dry summers and cool, moist winters. The mean annual precipitation is 250 to 300 mm, mean annual temperature is 6 to 7 degrees C, and the frost-free season is 70 to 100 days.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Bucan, Hunnton, Ninemile, Pequop and Wieland soils. Bucan, Ninemile, Pequop and Wieland soils lack an indurated duripan. Hunnton soils lacks a Mollic epipedon.

DRAINAGE AND SATURATED HYDRAULIC CONDUCTIVITY: Well drained; medium or rapid runoff; moderately low saturated hydraulic conductivity.

USE AND VEGETATION: Rangeland and wildlife habitat. The vegetation is mainly Wyoming big sagebrush, basin big sagebrush, Sandberg bluegrass, basin wildrye, bluebunch wheatgrass, and Thurber needlegrass.

DISTRIBUTION AND EXTENT: Northeast Nevada. MLRA 25. These soils are not extensive.

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

SERIES ESTABLISHED: Northwest Area, Elko County, Nevada. l986.

REMARKS: Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon - The zone from the surface of the soil to a depth of 25 cm (A1 and A2 horizons).
Argillic horizon - The zone from 25 to 64 cm (Bt and Btk horizons).
Duripan - The zone from 64 to 69 cm (Bqkm horizon).
Lithic contact - The boundary at 69 cm (R layer).
Particle-size control section - The zone from 25 to 64 cm (Bt and Btk horizons).

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National Cooperative Soil Survey
U.S.A.