LOCATION ABROJO NMEstablished Series
TAXONOMIC CLASS: Ashy-skeletal, glassy, nonacid, mesic Vitritorrandic Ustorthents
TYPICAL PEDON: Abrojo extremely cobbly ashy loamy coarse sand, extremely bouldery--on a backslope of a mesa sloping 50 percent to the south at 6,490 feet elevation--rangeland. (Colors are for dry soil unless otherwise noted. When described on November 10, 1999, the soil was dry throughout.)
Surface is covered with 35 percent gravel, 30 percent cobbles, 10 percent stones, and 15 percent boulders.
A--0 to 2 inches; light brown (7.5YR 6/3) extremely cobbly ashy loamy coarse sand, brown (7.5YR 4/3) moist; weak medium platy structure parting to weak fine granular structure; soft, very friable, nonsticky and nonplastic; common fine and many very fine roots; common very fine irregularly shaped pores; 30 percent gravel, 25 percent cobbles, 10 percent stones and 15 percent boulders; neutral (pH 7.2); abrupt smooth boundary. (2 to 4 inches thick)
C1--2 to 9 inches; pink (7.5YR 7/3) very gravelly ashy loamy coarse sand, brown (7.5YR 5/3) moist; single grain; loose, nonsticky and nonplastic; few medium, common fine, and many very fine roots; common very fine irregularly shaped pores; 30 percent gravel and 10 percent cobbles; slightly alkaline (pH 7.4); clear smooth boundary. (12 to 32 inches thick)
C2--9 to 23 inches; pink (7.5YR 7/3) very gravelly ashy loamy coarse sand, brown (7.5YR 5/3) moist; single grain; loose, nonsticky and nonplastic; few coarse, common medium, common fine, and common very fine roots; 25 percent gravel, 10 percent cobbles, and 5 percent stones; moderately alkaline (pH 8.2); clear smooth boundary. (12 to 32 inches thick)
C3--23 to 30 inches; pink (7.5YR 7/3) very cobbly ashy loamy coarse sand, brown (7.5YR 5/3) moist; single grain; loose, nonsticky and nonplastic; few very coarse, few coarse, few medium, common fine, and common very fine roots; 20 percent gravel, 15 percent cobbles, and 5 percent stones; moderately alkaline (pH 8.0); abrupt wavy boundary. (12 to 32 inches thick)
2C4--30 to 64 inches; white (7.5YR 8/1) ashy loamy sand, light gray (7.5YR 7/1) moist; massive; soft, very friable, slightly sticky and nonplastic; few medium and few fine roots; few fine and few very fine tubular pores; strongly alkaline (pH 8.8); abrupt wavy boundary. (26 to 40 inches thick)
3C5--64 to 80 inches; reddish yellow (7.5YR 7/6) gravelly ashy loamy coarse sand, strong brown (7.5YR 5/6) moist; single grain; loose, nonsticky and nonplastic; 25 percent gravel; very strongly alkaline (pH 9.1).
TYPE LOCATION: Bandelier National Monument, Tsankawi section, Santa Fe County, New Mexico; about 2.75 miles north of White Rock; USGS White Rock 7.5 minute topographic quadrangle; Latitude 35 degrees 51 minutes 35 seconds North and Longitude 106 degrees 12 minutes 55 seconds West, NAD 27.
RANGE IN CHARACTERISTICS:
Soil moisture: The soil moisture control section is moist in all parts during the 60 days following the winter solstice. It is moist in some part less than 40 percent and moist in all parts less than 25 percent of the time when the soil temperature at 20 inches is above 41 degrees F. The soils are driest in May and June. The soil moisture regime is ustic bordering on aridic.
Average annual soil temperature: 50 to 52 degrees F.
Lithology of fragments: rhyolitic tuff
Volcanic glass content: 70 to 90 percent in the coarse silt plus sand fraction
Particle-size control section:
Sand content: 75 to 90 percent
Rock fragment content: 35 to 60 percent
Volcanic glass content: 70 to 90 percent in the coarse silt plus sand fraction
A horizon
Hue: 5YR to 10 YR
Value: 4 to 6 dry, 3 to 5 moist
Chroma: 2 or 3, dry or moist
Clay content: 4 to 8 percent
Rock fragments: total range is 60 to 85 percent
25 to 35 percent gravel
15 to 25 percent cobbles
5 to 10 percent stones
5 to 15 percent boulders
C horizons
Hue: 5YR to 10YR
Value: 5 to 7 dry, 4 to 6 moist
Chroma: 2 to 6 dry, 3 to 6 moist
Texture: very cobbly or very gravelly-ashy coarse sand, ashy loamy coarse sand, or ashy loamy
sand
Clay content: 4 to 8 percent
Sand content: 75 to 90 percent
Fine sand or coarser content: 70 to 85 percent
Salinity, mmhos/cm: 0 to 2 in the upper part, 2 to 4 in the lower part
Sodicity, SAR: 0 to 4 in the upper part, 5 to 13 in the lower part
Rock fragments: total range is 35 to 60 percent
25 to 35 percent gravel
5 to 15 percent cobbles
0 to 5 percent stones
Reaction: slightly alkaline or moderately alkaline
2C4 horizon
Hue: 2.5YR to 10YR
Value: 7 or 8 dry, 5 to 7 moist
Chroma: 1 to 6 dry, 1 to 8 moist
Texture: ashy coarse sand, ashy sand, ashy loamy coarse sand, ashy loamy sand, or ashy loamy fine sand
Clay content: 4 to 8 percent
Sand content: 75 to 90 percent
Fine sand or coarser content: 70 to 85 percent
Salinity, mmhos/cm: 0 to 2
Sodicity, SAR: 5 to 13
Rock fragments - 0 to 10 percent gravel
3C5 horizon
Value: 6 or 7 dry, 5 or 6 moist
Chroma: 5 or 6, dry or moist
Clay content: 4 to 8 percent
Salinity, mmhos/cm: 2 to 4
Sodicity, SAR: 13 to 30
Rock fragments: 20 to 30 percent gravel
Reaction: strongly alkaline or very strongly alkaline
COMPETING SERIES: There are no competing series.
GEOGRAPHIC SETTING: Abrojo soils are on south-facing backslopes of mesas, undulating plateaus, and canyons. They formed in colluvium over residuum derived from rhyolitic tuff of the Quaternary age Bandelier Tuff formation. Slopes are 25 to 65 percent. Elevation ranges from 5,700 to 7,200 feet. The mean annual precipitation is 14 to 16 inches with about 45 percent falling as rain from high-intensity convective thunderstorms between July and September. The mean annual air temperature is 48 to 50 degrees F. The frost-free period is 140 to 160 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Chiminet and Piojillo soils. Chiminet soils are ashy, very shallow, and occur on south-facing upper backslopes of mesas. Piojillo soils are ashy, are very deep, and occur on footslopes of valley sides.
DRAINAGE AND PERMEABILITY: Somewhat excessively drained; low surface runoff; rapid permeability.
USE AND VEGETATION: Abrojo soils are used for recreation, wildlife habitat, and watershed. The historic climax vegetation is blue grama, black grama, galleta, skunkbush sumac, and oneseed juniper. The ecological site is Hills (R036XB124NM).
DISTRIBUTION AND EXTENT: Abrojo soils are of small extent on the southwestern Espanola Basin part of the Basin and Range province in northcentral New Mexico. The MLRA is 36.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana
SERIES ESTABLISHED: Santa Fe County, New Mexico; Santa Fe Area Soil Survey Update, 2008. Abrojo is the Spanish word for thistle.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - The zone from 0 to about 2 inches. (A horizon)
Vitritorrandic feature - based on volcanic glass content throughout the upper 30 inches (A, C1, C2, and C3 horizons).
Classified according Keys to Soil Taxonomy Tenth Edition, 2006.