LOCATION OVERTON                 NV

Established Series
Rev. ELS
12/2015

OVERTON SERIES

The Overton series consists of deep, very poorly drained soils that formed in clayey alluvium from sedimentary rocks. Overton soils are on flood plains and have less than 1 percent slope. The mean annual precipitation is about 5 inches and the mean annual air temperature is about 65 degrees F.

TAXONOMIC CLASS: Fine, smectitic, calcareous, thermic Aeric Endoaquepts

TYPICAL PEDON: Overton silty clay, cultivated. (Colors are for dry soil unless otherwise noted.)

Ap--0 to 7 inches; gray (2.5Y 5/1) silty clay, gray (2.5Y 6/1) crushed, very dark grayish brown (2.5Y 3/2) moist; dark grayish brown (2.5Y 4/2) moist crushed; moderate coarse and medium subangular blocky structure; very hard, friable, very sticky and very plastic; many very fine and fine roots; many very fine and fine tubular pores; violently effervescent; strongly alkaline (pN 8.6); clear smooth boundary. (5 to 8 inches thick)

A1--7 to 16 inches; gray (2.5Y 5/1) clay, gray (2.5Y 6/1) crushed, very dark grayish brown (2.5Y 3/2) moist, dark grayish brown (2.5Y 4/2) moist crushed; weak coarse prismatic structure that parts to moderate medium subangular blocky structure; very hard, firm, very sticky and very plastic; many very fine and fine roots; many very fine and fine tubular pores; violently effervescent; strongly alkaline (pH 8.6); abrupt smooth boundary. (5 to 10 inches thick)

B1g--16 to 19 inches; light gray (5Y 6/1) silty clay, gray (5Y 5/1) moist; many fine and medium faint gray (5Y 5/1), many fine prominent reddish brown (5YR 4/4), and many fine distinct very dark grayish brown (2.5Y 3/2) mottles; very few fine prominent white (10YR 8/2) gypsum flecks; weak medium and coarse prismatic structure; hard, firm, very sticky and very plastic; many very fine roots; many very fine tubular pores; violently effervescent; strongly alkaline (pH 8.6); clear wavy boundary. (3 to 13 inches thick)

C1g--19 to 25 inches; pale yellow (5Y 8/3) silty clay, pale olive (5Y 6/3) moist; many medium and fine prominent brown (7.5YR 4/4) and strong brown (7.5YR 5/8) mottles; weak medium prismatic structure; hard, friable, very sticky and very plastic; common very fine roots; many very fine and fine tubular pores; violently effervescent; strongly alkaline (pH 8.6); abrupt wavy boundary. (4 to 10 inches thick)

C2--25 to 30 inches; pale yellow (2.5Y 7/4) and very pale brown (10YR 7/3) finely stratified fine sandy loam and clay loam, light yellowish brown (2.5Y 6/4) and pale brown (10YR 6/3) moist; many coarse distinct strong brown (7.5YR 5/8) mottles; weak medium and fine granular structure; slightly hard and hard, friable, nonsticky and sticky, nonplastic and plastic; common very fine roots; many very fine and fine interstitial pores; violently effervescent; strongly alkaline (pH 8.6); abrupt wavy boundary. (2 to 8 inches thick)

C3--30 to 60 inches; light reddish brown (5YR 6/4) silty clay, reddish brown (5YR 4/4) moist; few fine faint yellowish red (5YR 5/6) mottles and few thin 1/8 inch strata of reddish brown (2.5YR 4/4); weak thick platy structure; very hard, firm, very sticky and very plastic; few very fine and fine roots; many very fine and fine tubular pores; violently effervescent; strongly alkaline (pH 8.6).

TYPE LOCATION: Clark County, Nevada; on the Keith Adams Ranch in Moapa Valley, approximately 400 feet north and 100 feet east of center sec. 22, T.15S., R.67E.

RANGE IN CHARACTERISTICS: The calcium carbonate equivalent ranges from 5 to 25 percent but any one horizon has less than 5 percent secondary calcium carbonate. pH ranges from 8.2 to 9.4. Mean annual soil temperature is about 67 degrees F. The soil is moist more than half the time and is usually saturated for periods longer than one month during the spring unless drained. The control section is dominantly silty clay or clay but has thin (less than 6 inches thick) strata of material ranging from clay loam to loamy fine sand in some pedons. It ranges from 35 to 60 percent clay.

The A horizon has hue of 2.5Y or 5Y, value of 5 or 6 dry, 3 or 4 moist, but never both 5 dry and 3 moist after crushing, and chroma of 1 or 2. The Ap horizon has weak or moderate, medium or coarse subangular blocky structure and the lower part of the A horizon has weak medium to very coarse prismatic structure that parts to weak or moderate subangular or angular blocky.

The upper part of the C horizon has hue of 5Y or 2.5Y, value of 6 through 8 dry, 4 or 5 moist, and chroma of 1 through 3. It is mottled with common or many, fine to large high chroma greenish and bluish mottles and some low chroma mottles. The lower part of the C horizon has hue of 2.5Y through 5YR, value of 6 or 7 dry, 5 or 6 moist, and chroma of 2 through 4. It is also mottled, similar to the upper part of the C horizon. Lime is usually well disseminated but fine or medium soft lime masses are in the lower part of the A1 or upper part of the C horizon in some pedons. Gypsum and salt crystals are in most pedons.

COMPETING SERIES: This is the Glann series. Glann soils have less than 35 percent clay in the particle size control section and have irregularly decreasing organic matter with increasing depth.

GEOGRAPHIC SETTING: Overton soils are on smooth, nearly level flood plains at elevations of about 1,400 feet. Slopes are commonly less than 0.3 percent, but range up to 1 percent. The soils formed in clayey alluvium derived from mixed sedimentary rocks and reworked lacustrine material. The climate is arid and hot. The mean annual rainfall is 4 to 6 inches. Average annual temperature is about 65 degrees F., January temperature about 45 degrees F., and July temperature about 83 degrees F. The frost-free season is about 240 days.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Toquop, Calico, and Virgin River soils. Calico soils have a coarse-loamy over fine textured control section and lack mottles in the coarse-loamy material. Toquop soils have a sandy control section and are never saturated. Virgin River soils are never saturated and lack mottles above a depth of 20 inches.

DRAINAGE AND PERMEABILITY: Very poorly drained; very slow runoff; slow permeability.

USE AND VEGETATION: Host of these soils are drained as a result of flood control measures and are irrigated and cropped to alfalfa, sorghum, small grains, mixed legume and grass pastures, and sugar beets for seed. The principal vegetation where not irrigated is quailbush, mesquite, fourwing saltbush, and saltgrass. These areas are used for limited livestock grazing.

DISTRIBUTION AND EXTENT: These soils are in the Moapa Valley of the Virgin River Area, Nevada. The series is of small extent but may occur in adjacent areas in southwestern Utah.

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

SERIES ESTABLISHED: Clark County (Virgin River Area), Nevada, 1970.

OSED scanned by SSQA. Last revised by state on 12/76.

Responsibility for this series was transferred from Davis to Phoenix 12/2015. ET

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National Cooperative Soil Survey
U.S.A.