LOCATION PASTORIUS CO+NM
Established Series
Rev. JPP/TWH/KLS
03/2018
PASTORIUS SERIES
The Pastorius series consists of very deep well drained soils that formed in cobbly alluvium. Pastorius soils are on river or stream terraces and have slopes of 1 to 6 percent. The mean annual precipitation is about 508 mm and the mean annual temperature is about 6.1 degrees C.
TAXONOMIC CLASS: Loamy-skeletal, mixed, superactive, frigid Pachic Argiustolls
TYPICAL PEDON: Pastorius cobbly loam, rangeland. (Colors are for dry soil unless otherwise stated.)
A1--0 to 18 cm; brown (7.5YR 4/2) cobbly loam, dark brown (7.5YR 3/2) moist; moderate fine granular structure; soft, friable, slightly sticky and slightly plastic; many fine and very fine roots; 15 percent cobbles; slightly acid (pH 6.3); gradual smooth boundary.
A2--18 to 51 cm; brown (7.5YR 4/2) cobbly loam, dark brown (7.5YR 3/2) moist; moderate medium granular structure; slightly hard, friable, slightly sticky and slightly plastic; 20 percent cobbles and 5 percent gravel; slightly acid (pH 6.4) clear smooth boundary. (combined thickness of A1, A2 is 30 to 70 cm)
Bt1--51 to 61 cm; reddish brown (5YR 5/4) very cobbly clay loam, dark reddish brown (5YR 3/4) moist; weak medium subangular blocky structure; hard, firm, moderately sticky and moderately plastic; few distinct clay films on faces of peds; 25 percent cobbles and 25 percent gravel; neutral (pH 6.8) clear smooth boundary. (3 to 9 inches thick)
Bt2--61 to 99 cm; reddish brown (5YR 4/4) extremely cobbly clay loam, dark reddish brown (5YR 3/4) moist; moderate fine subangular blocky structure; hard, firm, moderately sticky and moderately plastic; many prominent clay films on faces of peds and as patches on rock fragments; 50 percent cobbles and 20 percent gravel; neutral (pH 6.8) gradual smooth boundary. (combined thickness of Bt1, Bt2 is 30 to 100 cm)
BC--99 to 142 cm; reddish brown (5YR 5/4) extremely cobbly sandy clay loam, reddish brown (5YR 4/4) moist; weak fine subangular blocky structure; slightly hard, friable, slightly sticky and nonplastic; few distinct clay films on faces of peds and on rock fragments; 65 percent cobbles and 15 percent gravel; neutral (pH 7.0) gradual smooth boundary. (15 to 61 cm thick)
2C--142 to 183 cm; extremely cobbly sand; 50 percent cobbles and 15 percent gravel; neutral.
TYPE LOCATION: La Plata County, Colorado; about 5 kilometers north of Hesperus along La Plata Canyon Road about 15 meters west of the road near the northwest corner of Sec. 3, T. 35 N., R. 11 W. U.S.G.S. Hesperus quad.; Lat. 37 degrees, 19 minutes, 36 seconds N., and Long. 108 degrees, 03 minutes, 45 seconds W. NAD 27.
RANGE IN CHARACTERISTICS:
Mean annual soil temperature: 5.6 to 8.3 degrees C.
Mean summer soil temperature: 15.6 to 17.8 degrees C.
Thickness of the mollic epipedon: 43 to 61 cm
Numerous stones and boulders up to 72 cm (2.5 feet) in diameter occur throughout the soil.
The soil is typically noncalcareous throughout.
Particle-size control section (weighted average):
Clay content: 25 to 35 percent
Rock fragment content: 35 to 75 percent
A horizon(s)
Hue: 5YR to 10YR
Value: 4 or 5 dry, 2 or 3 moist
Chroma: 1 to 3, dry or moist
Rock fragment content: 5 to 35 percent
Reaction (pH): 6.1 to 7.3
Bt horizon(s)
Hue: 2.5YR to 7.5YR
Value: 4 or 5 dry, 3 or 4 moist
Chroma: 3 to 6, dry or moist
Texture: extremely cobbly sandy clay loam, extremely cobbly sandy clay loam, very cobbly clay loam, very gravelly clay loam, cobbly loam
Clay content: 20 to 35 percent
Sand content: 30 to 70 percent
Rock fragment content: Cobbles range from 10 to 60 percent, gravel from 5 to 40 percent, and stones from 0 to 15 percent
Reaction (pH): 6.1 to 7.8
2C horizon
Texture: extremely cobbly sand, extremely gravelly loamy sand, extremely gravelly sandy loam, extremely gravelly sand.
Clay content: 0 to 10 percent.
Rock fragment content: 10 to 50 percent gravel, 20 to 50 percent cobbles, 0 to 15 percent stones.
Reaction (pH): 6.6 to 7.3
COMPETING SERIES:
Adellern (NM) - have horizons of calcium carbonate accumulation
Braziel soils (MT) - have hue greater than 7.5YR in the Bt horizons
Fessler (MT) - have horizons of calcium carbonate accumulation
Mapache soils (NM) - do not have a lithologic discontinuity
Pastorpeak (AZ) - have horizons of calcium carbonate accumulation
Zillion soils (UT) - have horizons of calcium carbonate accumulation
GEOGRAPHIC SETTING:
Landform - river or stream terraces
Elevation - 2,250 to 2,745 meters
Slopes - 1 to 6 percent
Parent material - cobbly alluvium
Mean annual air temperature - 4.4 to 7.2 degrees C.
Mean summer air temperature - 14.4 to 18.3 degrees C.
Mean annual precipitation - 460 to 580 mm; about 1/2 to 2/3 of this comes as snow
Frost-free period - 80 to 115 days
GEOGRAPHICALLY ASSOCIATED SOILS: None listed.
DRAINAGE AND PERMEABILITY: Well drained; low runoff; moderate to moderately slow permeability.
USE AND VEGETATION: These soils are used for range and irrigated pasture. Native vegetation is Arizona fescue, mountain muhly, slender wheatgrass, Junegrass, Gambel oak, fringed sage, and rabbitbrush.
DISTRIBUTION AND EXTENT: Southwest Colorado and northwest New Mexico. LRR D, E; MLRA 36, 48A; moderate extent.
SOIL SURVEY REGIONAL OFFICE (SSRO) RESPONSIBLE: Bozeman, Montana
SERIES ESTABLISHED: La Plata County Area, Colorado, 1982. The name is from a reservoir.
REMARKS:
Diagnostic horizons and features recognized in this pedon:
Mollic epipedon: 0 to 51 cm (A1 and A2 horizons)
Argillic horizon: 51 to 99 cm (Bt1 and Bt2 horizons)
Lithologic discontinuity: 142 to 183 cm (2C horizon)
Particle-size control section: 51 to 99 cm (Bt horizons)
Pastorius soils have a frigid temperature regime and are in an ustic soil moisture regime with a typic subclass.
National Cooperative Soil Survey
U.S.A.