LOCATION CURHOLLOW UT+AZEstablished Series
TAXONOMIC CLASS: Loamy-skeletal, mixed, superactive, mesic, shallow Calcic Petrocalcids
TYPICAL PEDON: Curhollow very gravelly fine sandy loam--rangeland. (Colors are for dry soil unless otherwise noted.)
A--0 to 3 inches; brown (7.5YR 5/4) very gravelly fine sandy loam, dark brown (7.5YR 3/4) moist; moderate very fine granular structure; soft, very friable, slightly sticky and nonplastic; few fine and common very fine roots; few fine and common very fine interstitial pores; 50 percent pebbles; slightly effervescent; strongly alkaline (pH 8.5); clear smooth boundary. (2 to 5 inches thick)
Bk1--3 to 10 inches; light brown (7.5YR 6/4) very gravelly loam, dark brown (7.5YR 3/4) moist; weak fine subangular blocky structure; slightly hard, very friable, slightly sticky and slightly plastic; few fine and medium and common very fine roots; few fine and medium and common very fine tubular pores; 45 percent pebbles and some cobbles; strongly effervescent, carbonates are disseminated; strongly alkaline (pH 8.6); clear wavy boundary. (5 to 12 inches thick)
Bk2--10 to 15 inches; light brown (7.5YR 6/4) very gravelly fine sandy loam, brown (7.5YR 5/4) moist; moderate very fine granular structure; slightly hard, very friable, slightly sticky and slightly plastic; few fine, common very fine roots; few fine, common very fine interstitial pores; 55 percent pebbles and some cobbles; strongly effervescent, carbonates are disseminated; strongly alkaline (pH 8.5); abrupt wavy boundary. (0 to 7 inches)
Bkm--15 inches; indurated petrocalcic horizon.
TYPE LOCATION: Washington County, Utah; about 12 miles southwest of St. George, 4.5 miles southeast of the Apex mine in the Beaver Dam Mountains, and 3.5 miles west of where the Virgin River crosses the Utah-Arizona state line; 1,580 feet east and 200 feet north of the southwest corner of section 28, T. 43 S., R. 17 W; USGS Jarvis Peak 7.5 minute topographic quadrangle; 37 degrees 0 minutes 34 seconds north latitude and 113 degrees 45 minutes 51 seconds west longitude, NAD 27.
RANGE IN CHARACTERISTICS:
Soil moisture - The soils are usually dry during the period the soil temperature is above 41 degrees F. They are moist in some parts of the moisture control section for 30 to 40 days during the summer months and are dry for 70 to 85 days during the 120 days following the winter solstice. Ustic aridic moisture regime.
Soil temperature - 54 to 58 degrees F.
Mean summer soil temperature - 71 to 76 degrees F.
Depth to thin petrocalcic horizon - 10 to 20 inches.
Control section - Clay content: averages 18 to 27 percent; Fine sand or coarser content: 40 to 60 percent;
Rock fragments: 35 to 90 percent, mainly pebbles and cobbles. Lithology of fragments is typically sedimentary rocks such as limestone or sandstone.
Reaction - Slightly alkaline to strongly alkaline.
A horizon
Hue: 5YR to 10YR.
Value: 4 to 6 dry, 3 or 4 moist.
Chroma: 2 to 6, dry or moist.
Rock fragments: 25 to 85 percent.
Bk horizons
Hue: 5YR to 10YR.
Value: 4 to 8 dry, 3 to 7 moist.
Chroma: 3 to 6, dry or moist.
Texture: Very gravelly loam, extremely gravelly loam, very cobbly loam, extremely cobbly loam, very gravelly sandy loam, very gravelly silt loam or very gravelly sandy clay loam.
Rock fragments: 35 to 90 percent, mainly pebbles and cobbles.
Identifiable secondary carbonates: Carbonates commonly coat undersides of rock fragments, but may be disseminated in the horizon matrix.
Effervescence: Strongly effervescent or violently effervescent.
Calcium carbonate equivalent: 15 to 30 percent.
COMPETING SERIES: These are the Childers (AZ), Havasupai (AZ), Pibler (UT) and Pinetown (UT) series. Childers soils have 5 to 18 percent clay in the particle-size control section and are 20 to 40 inches to lithic contacts underlying the petrocalcic horizon. Havasupai soils have extremely gravelly sand below the hardpan. Pibler soils have a xeric moisture pattern and include very shallow depths to hardpan. Pinetown soils do not have bedrock within 25 inches and have mean annual soil temperature of 47 to 51 degrees F.
GEOGRAPHIC SETTING: Curhollow soils are on cuestas, mesas, plateaus, and pediments. They formed in alluvium and residuum derived from sedimentary or igneous rocks. Slopes are 1 to 35 percent. Elevations range from 3,500 to 6,100 feet. The mean annual precipitation is 10 to 14 inches. The mean annual temperature is 52 to 56 degrees F. and the mean summer temperature is 76 to 79 degrees F. The frost free period is 135 to 170 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Veyo and Yaki soils. Veyo soils are clayey-skeletal, shallow to petrocalcic horizons, and have argillic horizons. Yaki soils are loamy-skeletal, shallow to lithic contacts, and have carbonatic mineralogy and calcic horizons.
DRAINAGE AND PERMEABILITY: Well drained; medium or high surface runoff; moderate permeability in the horizons above the petrocalcic horizon.
USE AND VEGETATION: Curhollow soils are used for rangeland. The vegetation is Wyoming big sagebrush, pinyon, blackbrush, Mormon-tea, range ratany, yellowbrush, Indian ricegrass, cheatgrass, galleta, and cholla.
DISTRIBUTION AND EXTENT: Southwestern Utah and northern Arizona. This soil is moderately extensive. MLRAs 29 and 35.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Phoenix, Arizona
SERIES ESTABLISHED: Washington County, Utah, 1972.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - The zone from the soil surface to 3 inches (A horizon).
Calcic horizon - The zone from 3 to 15 inches (Bk1 and Bk2 horizons).
Petrocalcic horizon - The zone beginning at 15 inches (Bkm horizon).