LOCATION UNDERTON                NV

Tentative Series
Rev. DJM/BKP/ET
12/2015

UNDERTON SERIES

The Underton series consists of moderately deep over a petrocalcic, well drained soils that formed in alluvium predominantly from limestone. Underton soils are on erosional stream terraces. Slopes are from 2 to 8 percent. The mean annual precipitation is about 5 inches. The mean annual temperature is about 68 degrees F.

TAXONOMIC CLASS: Loamy-skeletal, carbonatic, thermic Argic Petrocalcids

TYPICAL PEDON: Underton extremely gravelly very fine sandy loam - rangeland. (Colors are for dry soil unless otherwise noted.) The soil surface is covered with 80 percent para gravels, 10 percent cobbles.

A--0 to 2 inches; light brown (7.5YR 6/4) extremely gravelly very fine sandy loam, strong brown (7.5YR 5/6) moist; strong very coarse platy structure; slightly hard, friable, slightly sticky and nonplastic; common fine roots and common very fine roots throughout; common very fine vesicular pores; 68 percent pebbles; 11 percent calcium carbonate equivalent; violently effervescent; moderately alkaline (pH 8.2); clear smooth boundary. (2 to 4 inches thick)

Btk1--2 to 7 inches; light brown (7.5YR 6/4) very gravelly fine sandy loam, strong brown (7.5YR 4/6) moist; weak fine and medium subangular blocky structure; slightly hard, very friable, slightly sticky and nonplastic; many very fine roots between peds; common very fine tubular pores; 20 percent faint clay films on ped faces; secondary calcium carbonate segregated few (2 percent) fine faint extremely weakly cemented carbonate masses in matrix and fine faint carbonate coatings on bottom surfaces of rock fragments; 40 percent pebbles, 5 percent cobbles; 22 percent calcium carbonate equivalent; violently effervescent; moderately alkaline (pH 8.2); clear wavy boundary. (3 to 6 inches thick)

Btk2--7 to 10 inches; reddish yellow (7.5YR 6/6) very gravelly sandy clay loam, strong brown (7.5YR 5/6) moist; weak medium subangular blocky structure; slightly hard, friable, moderately sticky and moderately plastic; many very fine and fine roots throughout; few fine tubular and common very fine interstitial pores; 25 percent distinct clay films on bottom surfaces of rock fragments; secondary calcium carbonate segregate as common moderately thick calcium carbonate pendants randomly oriented on surfaces of rock fragments; 45 percent pebbles, 5 percent cobbles; 23 percent calcium carbonate equivalent; violently effervescent; moderately alkaline (pH 8.4); clear wavy boundary. (3 to 4 inches thick)

Bkq--10 to 24 inches; pink (7.5YR 7/4) extremely gravely sandy clay loam, strong brown (7.5YR 5/6) moist; massive soft, very friable, slightly sticky, nonplastic; common fine roots and common very fine roots; few fine tubular and very fine tubular pores; secondary calcium carbonate segregated as medium (45 percent) distinct irregular weakly cemented carbonate masses in matrix and many medium distinct calcium carbonate pendants on bottom surfaces of rock fragments; secondary silica segregated as few (2 percent) very fine silica coats on bottom surfaces of rock fragments and on rock to rock contacts; 32 percent calcium carbonate equivalent; 65 percent pebbles and 10 percent cobbles; violently effervescent; moderately alkaline (pH 8.4); abrupt wavy boundary. (8 to 15 inches thick)

Bkm--24 to 46 inches; pinkish white (7.5YR 8/2) petrocalcic, pink (7.5YR 7/3) moist; strongly cemented, massive; few fine roots throughout and few very fine roots throughout; few fine tubular and few very fine tubular pores; 20 percent very fine distinct moderately cemented carbonate, finely disseminated in matrix; violently effervescent; strongly alkaline (pH 8.6).

TYPE LOCATION: Northeastern Clark County, Nevada; approximately 2 miles southeast of the Mormon Mesa VOR along the river access road in Halfway Wash; 1,160 feet east and 1,108 north of the southwest corner of section 4, T. 15 S., R. 69 E.; USGS Overton N.E., 7.5 minute topographic quadrangle; 36 degrees 44 minutes 33 seconds north latitude and 114 degrees 17 minutes 25 second west longitude, NAD 83; UTM 11s 741933e, 4069727n, NAS-C.

RANGE IN CHARACTERISTICS:
Soil moisture - Usually dry, moist in some part for short periods during winter and early spring and for brief periods between July and October following convection storms; typic aridic moisture regime.

Mean annual soil temperature 65 to 71 degrees F.

Depth to petrocalcic horizon - Ranges from 22 to 27 inches.

Rock fragments: 35 to 50 percent predominately pebbles with 2 to 10 percent cobbles.

Reaction - moderately alkaline or strongly alkaline.

Particle-size control section

Clay content: 8 to 18 percent
Rock fragments: averages 35 to 50 percent, mainly pebbles. Lithology of fragments are dominantly sedimentary rocks composed of limestone and dolomitic limestones.


A horizon

Value: 4 through 6 dry, 4 or 5 moist.
Chroma: 4 to 6 dry and 6 moist.

Btk horizons

Hue 7.5YR or 5YR.
Value: 5 or 6 dry, 4 or 5 moist.
Chroma: 4 through 6 dry, 6 moist.
Texture: fine sandy loam or sandy clay loam.
Rock fragments: 35 to 60 percent pebbles and cobbles.
Salinity (EC): 2 to 4 mmhos/cm.
Calcium carbonate equivalent: 10 to 35 percent in the less than 2 millimeter fraction and in the less than 20 millimeter fraction.

Other features: Few to common fine carbonate masses in matrix and many moderately to thick carbonate pendants on vertical and undersides of rock fragments. An increase in carbonate coatings occurs with depth.

Bkq horizon

Hue 7.5 or 5YR.
Value: 6 or 7 dry, 5 or 6 moist.
Chroma: 4 through 6 dry or moist.
Texture: sandy clay loam or sandy loam.
Clay content: Averages 15 to 25 percent.
Rock Fragments: 50 to 70 percent pebbles with 5 to 15 percent cobbles.
Calcium carbonate equivalent: 20 to 35 percent in the less than 2 millimeter fraction.
Other features: Calcium carbonate occurring as soft masses and moderately thick to thick coats on the undersides of rock fragments.

Bkm horizon

Cementation: Strongly cemented or indurated petrocalcic hardpan with less than 1 percent finely disseminated silica throughout.
Rock fragments: Gravelly or very gravelly within the petrocalcic matrix.
Other Features: Petrocalcic horizon ranges from 2 to 4 feet thick.

COMPETING SERIES: There are no competing series at this time.

GEOGRAPHIC SETTING: Underton soils are on erosional stream terraces. They typically occur on stream terrace summits and formed in alluvium derived from limestone clasts mixed with Tertiary sediments (Muddy Creek Formation). Slopes are from 2 to 8 percent. Elevations range from 1,400 to 2,000 feet. The climate is arid with warm, moist winters and hot, dry summers. The mean annual precipitation is about 5 to 7 inches, mean annual temperature is about 66 to 68 degrees F., and the frost-free period is 180 to 300 days.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Arizo and Bard series. Arizo lacks a petrocalcic horizon and an argillic horizon. Bard lacks an argillic horizon and has a loamy particle size control section.

DRAINAGE AND PERMEABILITY: Well drained; low runoff; moderately slow permeability.

USE AND VEGETATION: Rangeland and recreation use. The present vegetation is mainly white ratney, white bursage, creosotebush, turks head, Joshua tree, and barrel and cholla cactus.

DISTRIBUTION AND EXTENT: Southern Nevada. These soils are not extensive. MLRA 30.

MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: PHOENIX, ARIZONA

SERIES PROPOSED: Clark County, Nevada, 2004. The name is coined from the town of Overton.

REMARKS:

Additional data: This pedon has been sampled and characterized by the NSSL, reference S04NV-003002-1, 5.

Diagnostic horizons and features recognized in this pedon are:

Ochric epipedon - The zone from about 0 to 2 inches. (A horizon)

Argillic horizon - The zone from about 2 to 10 inches. (Btk horizons)

Calcic horizon - The zone from about 7 to 24 inches. (Btk horizons and Bkq horizons)

Petrocalcic horizon - The zone from about 24 to greater than 60 inches. (Bkm horizons)

Particle-size control section - The zone from 2 to 10 inches (6 to 26 centemeters) (The Btk horizon horizon).

Responsibility for this series was transferred from Davis to Phoenix 12/2015. The last revision to the series was 9/2004. ET

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National Cooperative Soil Survey
U.S.A.