LOCATION PASTORPEAK AZ+NMEstablished Series
TAXONOMIC CLASS: Loamy-skeletal, mixed, superactive, frigid Pachic Argiustolls
TYPICAL PEDON: Pastorpeak very cobbly very fine sandy loam, extremely stony -- on a planar backslope sloping 78 percent to the northeast at 8,880 feet elevation -- forest. (Colors are for dry soil unless otherwise noted. When described, the profile was dry throughout.)
Oi--0 to 2 inches; forest litter of needles, twigs, and cones; slightly decomposed just above soil surface; abrupt smooth boundary. (1 to 3 inches thick)
A--2 to 6 inches; dark reddish gray (5YR 4/2) very cobbly very fine sandy loam, dark reddish brown (5YR 3/2) moist; weak thick platy structure parting to moderate medium granular; soft, very friable, slightly sticky and nonplastic; common medium, fine, and very fine roots; common very fine irregularly shaped pores; 25 percent cobble, 10 percent flagstones, 10 percent channers, 5 percent stones, and 2 percent boulders; slightly acid (pH 6.4); clear smooth boundary. (3 to 7 inches thick)
Bt1--6 to 23 inches; reddish brown (5YR 4/3) very cobbly loam, dark reddish brown (5YR 3/3) moist; moderate coarse subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; few coarse, many medium, and common fine and very fine roots; few fine and very fine tubular pores; common faint clay films on faces of peds and lining pores; 25 percent cobble, 15 percent channers, and 5 percent flagstones; neutral (pH 6.6); gradual wavy boundary. (11 to 34 inches thick)
Bt2--23 to 40 inches; reddish brown (5YR 4/3) very cobbly loam, dark reddish brown (5YR 3/3) moist; moderate medium subangular blocky structure; soft, very friable, slightly sticky and slightly plastic; few coarse and common medium, fine, and very fine roots; common faint clay films on faces of peds and on rock fragments; 30 percent cobble, 10 percent flagstones, 10 percent channers, and 5 percent stones; neutral (pH 6.6); clear wavy boundary. (0 to 17 inches thick)
Btk--40 to 66 inches; reddish brown (5YR 5/4) extremely cobbly sandy loam, reddish brown (5YR 4/4) moist; weak fine granular structure; soft, very friable, slightly sticky and slightly plastic; few coarse and medium, many fine, and common very fine roots; common faint clay films on rock fragments; 35 percent cobble, 15 percent flagstones, 10 percent channers, 10 percent gravel, and 5 percent stones; noneffervescent in fine earth, strongly effervescent on undersides of larger rock fragments where secondary calcium carbonate are segregated in common large irregularly shaped accumulations; slightly alkaline (pH 7.6); clear irregular boundary. (20 to 32 inches thick)
Ctk--66 to 82 inches; fragmental; fragments separated by fractures wider than 1 cm which are devoid of fine earth, with some reddish brown (5YR 5/4) sandy loam present in fractures less than 1 cm wide, reddish brown (5YR 4/4) moist; massive, rock structure dominant except for minor amounts of granular fine earth; few fine and few very fine roots; very few thin clay films on rock fragments; 45 percent flagstones, 20 percent cobble, 15 percent channers, and 5 percent stones; very slightly effervescent in fine earth, violently effervescent on undersides of larger rock fragments where secondary calcium carbonate are segregated in common large irregularly shaped accumulations; moderately alkaline (pH 8.2).
TYPE LOCATION: Apache County, Arizona; on the Navajo Indian Reservation about 7.5 miles southwest of Teec Nos Pos; 275 feet west and 675 feet south of the northeast corner of section 36, T.40N., R.29E.; 36 degrees 50 minutes 13 seconds north latitude and 109 degrees 10 minutes 33 seconds west longitude.
RANGE IN CHARACTERISTICS:
Soil moisture - The soil moisture control section is moist in all parts from January to May and intermittently moist in some part from June to December. Moist in all parts less than 40 percent of the time (cumulative), when the soil temperature at 20 inches is 41 degrees F or higher. Driest during May and June. Typic ustic soil moisture regime.
Soil temperature - 44 to 47 degrees F.
Mean summer soil temperature - 59 to 62 degrees
Reaction - slightly acid in the surface to moderately alkaline in the substratum
Clay content - averages 18 to 27 percent
Rock fragments - 35 to 60 percent
Depth to base of Mollic epipedon - 16 to 38 inches
Depth to base of Argillic horizon - 50 to 60 inches or more
Depth to fragmental material - 60 to 80 inches
A horizon
Hue: 5YR, 7.5YR
Value: 4 or 5 dry
Chroma: 2 or 3, dry or moist
Organic carbon content: 2.4 to 4.2 percent
Clay content: 10 to 18 percent
Rock fragments: 35 to 60 percent
5 to 15 percent gravel and channers
25 to 30 percent cobble and flagstones
5 to 10 percent stones
0 to 5 percent boulders
Bt horizons
Hue: 5YR, 7.5YR
Value: 4 or 5 dry
Chroma: 2 or 3, dry or moist
Organic carbon content: 0.6 to 1.8 percent
Texture: loam, sandy clay loam
Clay content: 18 to 27 percent
Rock fragments: 35 to 60 percent
10 to 20 percent gravel and channers
25 to 35 percent cobble and flagstones
0 to 5 percent stones
Btk horizon
Hue: 5YR, 7.5YR
Chroma: 2 through 6, dry or moist
Texture: sandy loam, loam
Clay content: 18 to 24 percent
Calcium carbonate equivalent: 1 to 3 percent
Rock fragments: 60 to 80 percent
15 to 20 percent gravel and channers
40 to 50 percent cobble and flagstones
5 to 10 percent stones
Ctk horizon
Hue: 5YR, 7.5YR
Chroma: 2 through 6, dry or moist
Texture: fragmental
Calcium carbonate equivalent: 1 to 3 percent
Rock fragments: 80 to 95 percent
20 to 25 percent gravel and channers
55 to 60 percent cobble and flagstones
5 to 10 percent stones
COMPETING SERIES: These are the Adellern (NM), Braziel (MT), Fessler (MT), Mapache (NM), Pastorius (AZ) and Zillion (UT) series. Adellern soils are deeper than 40 inches to accumulations of calcium carbonate. Mapache soils formed in slope alluvium and colluvium derived from latite and dacite of the Tertiary age Tschicoma Formation and are slightly acid or neutral throughout. Pastorius soils are noncalcareous throughout. Zillion soils have clay contents in the particle-size control section ranging from 27 to 35 percent and the base of the argillic horizon is less than 30 inches. Braziel and Fessler soils are moist in May and June.
GEOGRAPHIC SETTING: Pastorpeak soils are on backslopes of mountains. They formed in colluvium and residuum derived from Tertiary quartz diorite and Jurassic sandstone. Slopes are 50 to 95 percent. Elevation ranges from 7,500 to 9,000 feet. The mean annual precipitation is 14 to 18 inches with more than 50 percent falling as snow from winter storms. The mean annual air temperature is 42 to 45 degrees F. The frost-free period is 100 to 120 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Bigpaw, Ligai, and Zibetod soils. Bigpaw soils are fine-silty and occur on footslopes. Ligai soils are moderately deep and occur on adjacent backslopes. Zibetod soils are shallow and occur on footslopes and shoulders of domes.
DRAINAGE AND PERMEABILITY: Well drained; rapid runoff; permeability is moderate in the solum and very rapid in the fragmental substratum.
USE AND VEGETATION: Pastorpeak soils are used for livestock grazing and timber production. Present vegetation is Douglas fir and ponderosa pine with an understory of nodding bromegrass, mountain snowberry, Gambel oak, western chokecherry, Utah serviceberry, rockspirea, and littleleaf mockorange.
DISTRIBUTION AND EXTENT: Pastorpeak soils are of small extent on the Carrizo Mountains portion of the Colorado Plateau province in northeast Arizona. MLRA is 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:
Mollic epipedon - The zone from 2 to 40 inches (A, Bt1, Bt2 horizons)
Pachic subgroup - The presence of a mollic epipedon that is greater than 16 inches thick
Argillic horizon - The zone from 6 to 66 inches (Bt1, Bt2, Btk horizons)
Keys to Soil Taxonomy - Soils classified according to the Eighth Edition, 1998.
ADDITIONAL DATA: Organic carbon values determined by Inter-Mountain Laboratories, Inc.