LOCATION SKYHAWK NM+AZEstablished Series
TAXONOMIC CLASS: Fine-silty, mixed, active, mesic Ustic Calciargids
TYPICAL PEDON: Skyhawk extremely gravelly sandy loam, extremely stony -- on the riser of a fan terrace sloping 42 percent to the south at 6,775 feet elevation -- rangeland. (Colors are for dry soil unless otherwise noted. When described, the pedon was dry throughout.)
A-- 0 to 2 inches; brown (7.5YR 5/3) extremely gravelly sandy loam, brown (7.5YR 4/3) moist; moderate thick platy structure parting to weak medium granular; soft, very friable, slightly sticky and slightly plastic; common fine and few very fine roots; few fine and common very fine irregularly shaped pores; 35 percent pebbles, 15 percent channers, 10 percent cobbles, 10 percent flagstones, and 5 percent stones; slightly effervescent; neutral (pH 7.0); abrupt smooth boundary. (1 to 3 inches thick)
Btk-- 2 to 6 inches; brown (7.5YR 5/4) gravelly clay loam, brown (7.5YR 4/4) moist; moderate coarse subangular blocky structure; slightly hard, friable, sticky and plastic; few fine and common very fine roots; common very fine tubular pores; common thin clay films on faces of peds and lining pores; 20 percent pebbles and 10 percent channers; strongly effervescent, secondary calcium carbonates segregated as very few fine irregularly shaped accumulations on faces of peds and few fine irregularly shaped accumulations on rock fragments; slightly alkaline (pH 7.8); abrupt wavy boundary. (3 to 9 inches thick)
2Bk1-- 6 to 13 inches; very pale brown (10YR 7/3) silty clay loam, pale brown (10YR 6/3) moist; moderate coarse prismatic structure parting to weak coarse subangular blocky; slightly hard, firm, sticky and plastic; few medium to very fine roots; few fine and common very fine tubular pores; 10 percent soft siltstone fragments; very few thin clay films on faces of peds and lining pores; strongly effervescent, secondary calcium carbonates segregated as common medium irregularly shaped accumulations on faces of peds and on rock fragments; strongly alkaline (pH 8.6); clear smooth boundary. (5 to 13 inches thick)
2Bk2-- 13 to 18 inches; light gray (2.5Y 7/2) silty clay loam, light olive brown (2.5Y 5/4) moist; moderate medium subangular blocky structure; slightly hard, firm, sticky and plastic; few fine and common very fine roots; few fine and very fine tubular pores; 10 percent soft siltstone fragments; strongly effervescent, secondary calcium carbonates segregated as few fine irregularly shaped accumulations on faces of peds and on rock fragments; strongly alkaline (pH 8.8); clear smooth boundary. (0 to 9 inches thick)
2Bk3-- 18 to 23 inches; light gray (2.5Y 7/2) silty clay loam, light olive brown (2.5Y 5/4) moist; weak medium subangular blocky structure; slightly hard, firm, sticky and plastic; common very fine roots; few very fine tubular pores; 30 percent soft siltstone fragments; strongly effervescent, secondary calcium carbonates segregated as few fine irregularly shaped accumulations on faces of peds and on rock fragments; strongly alkaline (pH 8.8); clear smooth boundary. (0 to 5 inches thick)
2Cy-- 23 to 35 inches; light brownish gray (2.5Y 6/2) silty clay loam, light olive brown (2.5Y 5/4) moist; massive, platy rock structure; hard, firm, sticky and plastic; common very fine roots; few very fine tubular pores; 80 percent soft siltstone fragments; secondary fine sand-sized gypsum crystals segregated in common fine irregularly shaped accumulations on rock fragments; strongly effervescent; strongly alkaline (pH 8.8); gradual smooth boundary. (9 to 14 inches thick)
2Cr-- 35 inches; interbedded siltstone and shale bedrock.
TYPE LOCATION: San Juan County, New Mexico; on the Navajo Indian Reservation about 7 miles north-northwest of Sanostee; 1,500 feet west and 1,350 feet north of the southeast corner of sec. 2, T.26N., R.20W.; Latitude 36 degrees 30 minutes 49 seconds N and Longitude 108 degrees 56 minutes 19 seconds W.
RANGE IN CHARACTERISTICS:
Soil moisture - Typically, the soil moisture control section (SMCS) is intermittently moist in some part from July through October and December to April 15. The SMCS is dry in all parts 50 to 75 percent of the time (cumulative) that the soil temperature at 20 inches is greater than 41 degrees F. Ustic aridic moisture regime.
Soil temperature - 52 to 54 degrees F.
Soil depth - 20 to 40 inches to soft bedrock
Depth to base of Argillic horizon - 4 to 10 inches
Depth to Calcic horizon - 4 to 10 inches
Soil reaction - neutral in the surface horizon to strongly alkaline in the substratum
Silicate clay content, control section weighted average - 27 to 35 percent
Organic carbon content - 0.6 to 1.2 percent in upper 16 inches
A horizon - Hue: 7.5YR or 10YR.
Value: 5 or 6 dry, 4 or 5 moist.
Chroma: 3 or 4.
Rock fragments: Total range is 60 to 80 percent; 40 to 50 percent pebbles and channers; 15 to 20 percent cobbles and flagstones; 5 to 10 percent stones.
2Btk horizon - Hue: 7.5YR or 10YR.
Value: 5 or 6 dry, 4 or 5 moist.
Calcium carbonate equivalent: 5 to 15 percent.
Texture: gravelly clay loam or gravelly loam.
Rock fragments: Total range is 15 to 35 percent; 15 to 30 percent pebbles and channers; 0 to 5 percent cobbles and flagstones.
3Bk horizons - Hue: 10YR or 2.5Y.
Value: 6 or 7 dry, 5 or 6 moist.
Chroma: 2 through 4.
Calcium carbonate equivalent: 15 to 25 percent.
Texture: silty clay loam or clay loam.
Salinity: less than 2 mmhos/cm.
Other features: 10 to 30 percent soft, slakable siltstone fragments.
3Cy horizon - Hue: 10YR or 2.5Y.
Value: 5 or 6 dry, 4 or 5 moist.
Chroma: 2 through 4.
Calcium carbonate equivalent: 10 to 15 percent.
Salinity: 2 to 4 mmhos/cm.
Other features: 50 to 80 percent soft, slakable siltstone fragments.
COMPETING SERIES: This is the Villedry (CO) series. Villedry soils average 15 to 30 inches to the base of the argillic horizon.
GEOGRAPHIC SETTING: Skyhawk soils are on risers of dissected fan terraces. They formed in alluvium derived from Tertiary basalt and residuum derived from Cretaceous siltstone. Slopes range from 35 to 50 percent. Elevation ranges from 5,800 to 7,200 feet. The mean annual precipitation is 8 to 12 inches about half of which falls as rain from high-intensity thunderstorms between July and September. The remainder falls as gentle rain or snow between December and mid-April. The mean annual temperature is 50 to 52 degrees F. The average frost-free period is 130 to 150 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Eagleye, Lavellga, and Toadlena soils. Eagleye soils are shallow to shale, lack diagnostic horizons, and occur on backslopes of structural benches. Lavellga soils are very deep, have carbonatic mineralogy, and occur on adjacent treads of fan terraces. Toadlena soils are shallow, contain gypsic horizons, and occur on summits and footslopes of structural benches.
DRAINAGE AND PERMEABILITY: Well drained; rapid runoff; moderately slow permeability.
USE AND VEGETATION: Skyhawk soils are used for livestock grazing. Present vegetation is blue grama, galleta, New Mexico feathergrass, black grama, fourwing saltbush, datil yucca, and scattered Utah juniper.
DISTRIBUTION AND EXTENT: Skyhawk soils are of small extent on the Four Corners Platform portion of the Colorado Plateau province in northwest New Mexico and northeast Arizona. MLRA 35.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Phoenix, Arizona
SERIES ESTABLISHED: Shiprock Area, Parts of San Juan County, New Mexico and Apache County, Arizona; 1993.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - The zone from the soil surface to a depth of about 2 inches. (A horizon)
Argillic horizon - The zone from 2 to about 6 inches. (2Btk horizon)
Calcic horizon - The zone from 6 to about 23 inches. (3Bk1, 3Bk2, and 3Bk3 horizons)
Paralithic contact - The presence of soft sedimentary bedrock at about 35 inches.
Particle-size control section - The zone from 2 to about 35 inches. (2Btk, 3Bk1, 3Bk2, 3Bk3, and 3Cy horizons)
Keys to Soil Taxonomy - Soils classified according to the Eighth Edition, 1998.
ADDITIONAL DATA: Salinity values were determined with an Instant EC kit. Calcium carbonate equivalence determined with a field volume calcimeter. Organic carbon values determined by Inter-Mountain Laboratories, Inc.