LOCATION CORTEZ                  NV

Established Series
Rev. RAF/RLB/JVC/JBF
01/2019

CORTEZ SERIES

The Cortez series consists of moderately deep to a duripan, well drained soils that formed in a surficial mantle of loess and volcanic ash over alluvium derived from mixed volcanic and sedimentary rocks. Cortez soils are on fan remnants. Slopes are 2 to 15 percent. The mean annual precipitation is about 230 mm and the mean annual temperature is about 8 degrees C.

TAXONOMIC CLASS: Fine, smectitic, mesic Vitrixerandic Natridurids

TYPICAL PEDON: Cortez ashy silt loam--rangeland. (Colors are for dry soil unless otherwise noted.)

A1--0 to 5 cm; light brownish gray (10YR 6/2) ashy silt loam, dark brown (10YR 3/3) moist; strong thick platy structure; slightly hard, very friable, nonsticky and slightly plastic; few very fine roots; common very fine vesicular pores; slightly alkaline (pH 7.7); abrupt smooth boundary. (3 to 15 cm thick)

A2--5 to 13 cm; light brownish gray (10YR 6/2) ashy silt loam, brown (10YR 4/3) moist; moderate very thin platy structure; slightly hard, very friable, nonsticky and slightly plastic; common very fine through medium roots, few very fine vesicular, few fine and very fine tubular and many very fine interstitial pores; moderately alkaline (pH 8.3); clear smooth boundary. (5 to 20 cm thick)

BAtn--13 to 25 cm; light gray (10YR 7/2) ashy silt loam, dark yellowish brown (10YR 3/4) moist; weak medium subangular blocky structure; hard, very friable, slightly sticky and slightly plastic; few very fine, and fine roots; many very fine tubular pores; few faint clay films lining pores; SAR is 9; strongly alkaline (pH 8.7); abrupt smooth boundary. (0 to 20 cm thick)

2Btnss--25 to 38 cm; brown (10YR 5/3) gravelly clay, brown (10YR 4/3) moist; strong medium prismatic structure; hard, firm, very sticky and very plastic; few very fine exped roots; few very fine tubular pores; very dark grayish brown (10YR 3/2) and dark brown (10YR 3/3) moist, organic coats on faces of peds; common distinct clay films lining pores; few slickensides on faces of peds; 15 percent gravel; SAR is 18; very strongly alkaline (pH 9.5); abrupt smooth boundary. (8 to 38 cm thick)

2Btnk--38 to 56 cm; brown (10YR 5/3) gravelly clay, dark brown (10YR 3/3) and dark yellowish brown (10YR 4/4) moist; massive; hard, firm, very sticky and very plastic; few very fine roots; few very fine tubular pores; common distinct clay films lining pores and many distinct clay bridges between sand grains; 15 percent gravel; strongly effervescent; secondary carbonates segregated in many fine seams; SAR is 20; very strongly alkaline (pH 9.6); abrupt smooth boundary. (5 to 28 cm thick)

2Bqkm--56 to 122 cm; very pale brown (10YR 7/3) cemented material, very pale brown (10YR 7/4) and light yellowish brown (10YR 6/4) moist; massive, extremely hard, extremely firm; indurated by opaline silica; few very fine roots matted on surface of pan; many distinct yellow (10YR 7/6) clay coats in the upper 8 cm; common very fine interstitial pores; strongly effervescent; strongly alkaline (pH 9.0); abrupt smooth boundary. (38 to 89 cm thick)

3Bq--122 to 152 cm; pale brown (10YR 6/3) very gravelly coarse sandy loam, brown (10YR 4/3) moist; massive; slightly hard, friable, nonsticky and nonplastic; many fine interstitial pores; common silica coats on sand grains and rock fragments; 25 percent gravel and 15 percent cobbles; strongly alkaline (pH 9.0)

TYPE LOCATION: Eureka County, Nevada; about 24 kilometers west of Carlin and 1.6 kilometers north of Interstate 80 on the east side of Bobs Flat; approximately 366 meters south and 579 meters west of the northeast corner of section 7, T. 32 N., R. 50 E.; USGS Bobs Flat 7.5 minute topographic quadrangle; latitude 40 degrees 39 minutes 44 seconds N and longitude 116 degrees 22 minutes 42 seconds W; WGS84 Decimal Degrees 40.6622222 latitude, -116.3783333 longitude.

RANGE IN CHARACTERISTICS:
Soil moisture: Usually moist in winter and spring, dry from June through October; aridic soil moisture regime that borders on xeric.
Mean annual soil temperature: 8 to 10 degrees C.
Depth to indurated duripan: 56 to 90 cm.
Other features: There is an abrupt boundary between the base of the eolian mantle and the top of the natric horizon.

Particle-size control section - Clay content: 40 to 50 percent;
Rock fragments: Average 10 to 15 percent.

A horizon
Value: 5 through 7 dry (greater 5.5 than when the upper 18 cm is mixed), 3 or 4 moist.
Chroma: 2 or 3, dry or moist.
Clay content: 5 to 10 percent.
Reaction: Neutral through moderately alkaline.
Volcanic glass content: 20 to 40 percent in coarse silt through fine sand fractions.
Oxalate aluminum plus one-half oxalate iron: 0.2 to 0.4 percent.

2Btnss and 2Btnk horizons
Hue: 10YR or 7.5YR.
Value: 5 or 6 dry, 3 through 5 moist.
Chroma: 2 through 4, dry or moist.
Texture: Clay, gravelly clay, or silty clay with some pedons having thin subhorizons of clay loam.
Clay content: 40 to 50 percent.
Structure: Moderate or strong, medium or coarse prismatic or columnar with some parts of the lower Btnk being subangular blocky, angular blocky or is massive.
Reaction: Moderately alkaline through very strongly alkaline.
Sodicity (SAR): 13 to 90.
Identifiable secondary carbonates: The 2Btnk horizon has common or many, fine or medium filaments and seams.
Calcium carbonate equivalent: 0 to 5 percent.

Bqkm horizon
Value: 6 through 8 dry, 4 through 7 moist.
Chroma: 1 through 4, dry or moist.
Reaction: Strongly alkaline or very strongly alkaline.

C horizon (when present)
Texture: Coarse sandy loam or loamy coarse sand.
Texture modifiers: Very gravelly or very cobbly.
Other features: In some pedons this horizon is moderately alkaline or saline-sodic.

COMPETING SERIES: This is the Flue series. Flue soils have Bq horizons formed in the lower part of the eolian mantle and have thin horizons high in carbonates between the natric horizon and the duripan.

GEOGRAPHIC SETTING: Cortez soils are on fan remnants. These soils formed in a surficial mantle of loess and volcanic ash over alluvium derived from mixed volcanic and sedimentary rocks. Slopes are 2 to 15 percent. Elevations range from 1,370 to 1,890 meters. The climate is semiarid with cool, moist winters and warm, dry summers. The mean annual precipitation is 200 to 250 mm, the mean annual temperature is 7 to 9 degrees C, and the frost-free period is 100 to 120 days.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Cherry Spring, Chiara, Orovada, and Tomera soils. Cherry Spring soils are fine-loamy and have a duripan that is not indurated. Chiara soils lack argillic horizons and are shallow to indurated duripans. Orovada soils are coarse-loamy and have cambic horizons. Tomera soils lack duripan and are very deep.

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

USE AND VEGETATION: Cortez soils are used for rangeland and wildlife habitat. The present vegetation is mainly Wyoming big sagebrush, Douglas rabbitbrush, basin wildrye, bottlebrush squirreltail, Sandberg bluegrass, mustard, cheatgrass, and other annuals.

DISTRIBUTION AND EXTENT: Northern Nevada. These soils are moderately extensive. The series concept and main acreage is in MLRA 25, while other acreage occurs in MLRA 24.

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

SERIES ESTABLISHED: Eureka County, (Tuscarora Mountain Area.) Nevada, 1979.

REMARKS: Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - The zone from the soil surface to 13 cm (A1 and A2 horizons).
Vitrandic intergrade feature - The zone from the soil surface to 25 cm (A1, A2, and BAtn horizons).
Abrupt textural change -The boundary at 25 cm (Between the BAtn and 2Btnss horizons).
Natric horizon - The zone from 25 to 56 cm (2Btnss and 2Btnk horizons).
Identifiable secondary carbonates - The zone from 38 to 122 cm (2Btnk and 2Bqkm horizons).
Duripan - The zone from 56 to 122 cm (2Bqkm horizon).
Particle-size control section - The zone from 25 to 56 cm (2Btnss and 2Btnk horizons).

The revision of November 2007 updated the taxonomic class from Fine, smectitic, mesic Xeric Natridurids based on the parent material for the eolian mantle and laboratory data on sand mineralogy for adjacent soils. Volcanic glass contents and oxalate extractable aluminum and iron values in the A horizons are estimated.

The BAtn horizon does not qualify as an argillic horizon nor is it part of the natric horizon because it lacks the required increase in clay content.

ADDITIONAL DATA: The typical pedon at the series type location has characterization data by the Soil Survey Laboratory (SSL), Riverside, CA as soil survey sample number S66NV-011-002 (pedon # 40A3167). The data is published in Soil Survey Investigations Report No. 23 on pages 38-39. Soil pH values in the typical pedon were determined in a soil-water (1:10) solution.

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National Cooperative Soil Survey
U.S.A.