LOCATION PEDREGAL NMEstablished Series
TAXONOMIC CLASS: Loamy-skeletal, mixed, superactive, mesic Aridic Paleustalfs
TYPICAL PEDON: Pedregal very gravelly loam--on the beveled summit of an erosional fan remnant sloping 8 percent to the north at 6,945 feet elevation--rangeland. (Colors are for dry soil unless otherwise noted. When described, the soil was slightly moist from 5 to 8 inches, but otherwise dry throughout.)
A--0 to 2 inches; brown (7.5YR 5/3) very gravelly loam, dark brown (7.5YR 3/3) moist; weak thick platy structure parting to moderate fine granular; soft, very friable, slightly sticky and nonplastic; few fine and common very fine roots; common very fine vesicular pores; 40 percent gravel and 5 percent cobbles; neutral (pH 7.2); abrupt smooth boundary. (1 to 3 inches thick)
Bt1--2 to 5 inches; reddish brown (5YR 4/3) very gravelly clay loam, dark reddish brown (5YR 3/4) moist; weak medium prismatic structure parting to moderate medium subangular blocky; moderately hard, firm, moderately sticky and moderately plastic; few coarse, few medium, few fine, and common very fine roots; few fine tubular and common very fine irregularly shaped pores; few distinct and few faint clay films on faces of peds and few faint clay bridges between very coarse sand grains; 35 percent gravel and 5 percent cobbles; neutral (pH 7.2); clear smooth boundary. (2 to 6 inches thick)
Bt2--5 to 8 inches; reddish brown (5YR 5/4) very gravelly clay loam, reddish brown (5YR 4/4) moist; weak coarse and moderate medium subangular blocky structure; moderately hard, firm, moderately sticky and moderately plastic; few coarse, few medium, few fine, and common very fine roots; few fine tubular and common very fine irregularly shaped pores; common distinct clay films on faces of peds and few faint clay bridges between very coarse sand grains and rock fragments; 40 percent gravel and 5 percent cobbles; slightly alkaline (pH 7.4); clear wavy boundary. (0 to 7 inches thick)
Btk--8 to 12 inches; light brown (7.5YR 6/3) very gravelly sandy clay loam, brown (7.5YR 5/4) moist; moderate medium subangular blocky structure; moderately hard, friable, moderately sticky and moderately plastic; few coarse, few medium, few fine, and common very fine roots; few fine tubular and common very fine irregularly shaped pores; few distinct and few faint clay films on faces of peds; 40 percent gravel and 5 percent cobbles; strongly effervescent, secondary calcium carbonate segregated as common fine and medium irregularly shaped coats on faces of peds and on rock fragments; moderately alkaline (pH 8.2); clear wavy boundary. (4 to 8 inches thick)
Bk1--12 to 22 inches; pinkish white (7.5YR 8/2) very gravelly sandy loam, pink (7.5YR 7/3) moist; moderate coarse subangular blocky structure; moderately hard, friable, slightly sticky and slightly plastic; few coarse, few medium, few fine, and few very fine roots; few fine and few very fine irregularly shaped pores; 45 percent gravel and 5 percent cobbles; violently effervescent, matrix is impregnated with secondary calcium carbonate; moderately alkaline (pH 8.4); clear wavy boundary. (6 to 16 inches thick)
Bk2--22 to 45 inches; pink (7.5YR 7/3) extremely gravelly coarse sandy loam, light brown (7.5YR 6/4) moist; moderate thin platy structure; slightly hard, very friable, slightly sticky and nonplastic; few medium, few fine, and few very fine roots; 55 percent gravel, 15 percent cobbles, and 1 percent stones; violently effervescent, secondary calcium carbonate segregated as many medium and coarse irregularly shaped coats on rock fragments; moderately alkaline (pH 8.4); clear irregular boundary. (8 to 28 inches thick)
BCk--45 to 62 inches; strong brown (7.5YR 5/6) extremely gravelly coarse sand, strong brown (7.5YR 4/6) moist; single grain; loose, nonsticky and nonplastic; few very fine roots; 55 percent gravel and 10 percent cobbles; slightly to strongly effervescent, secondary calcium carbonate segregated as few fine irregularly shaped coats on rock fragments; slightly alkaline (pH 7.4); clear wavy boundary. (11 to 21 inches thick)
C1--62 to 81 inches; strong brown (7.5YR 5/6) gravelly loamy sand, strong brown (7.5YR 4/6) moist; massive; soft, very friable, slightly sticky and nonplastic; few very fine roots; 30 percent gravel; noneffervescent in spots to slightly effervescent elsewhere; slightly alkaline (pH 7.6); abrupt smooth boundary. (12 to 25 inches thick)
2C2--81 to 92 inches; reddish brown (5YR 5/4) silt loam, reddish brown (5YR 4/4) moist; massive, platy rock structure; hard, firm, slightly sticky and moderately plastic; noneffervescent in spots to strongly effervescent elsewhere; strongly alkaline (pH 8.6); clear smooth boundary. (0 to 12 inches thick)
2C3--92 to 104 inches; light reddish brown (5YR 6/4) silt loam, reddish brown (5YR 4/4) moist; massive, platy rock structure; hard, firm, slightly sticky and moderately plastic; strongly effervescent; strongly alkaline (pH 8.6).
TYPE LOCATION: Santa Fe County, New Mexico; about 1 mile west of the Village of Tesuque; 700 feet west and 2,500 feet north of the southeast corner of section 26, T.18N., R.9E.; USGS Tesuque 7.5 minute topographic quadrangle; Latitude 35 degrees 45 minutes 41.5 seconds North and Longitude 105 degrees 56 minutes 55.5 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.
Mean annual soil temperature - 49 to 52 degrees F.
Depth to base of argillic horizon - 10 to 19 inches
Depth to calcareous material (as visible secondary calcium carbonate) - 5 to 12 inches
Depth to calcic horizon - 10 to 19 inches
Lithology of rock fragments: granite, gneiss, and schist
Particle-size control section (weighted averages)
Silicate clay content: 27 to 34 percent
Sand content: 35 to 60 percent
Fine sand or coarser content: 35 to 55 percent
Rock fragment content: 35 to 60 percent
Reaction - neutral in the surface and the upper part of the subsoil; slightly alkaline in the lower part of the subsoil; moderately alkaline in the upper part of the substratum; slightly alkaline to strongly alkaline in the lower part of the substratum
Salinity, mmhos/cm - 0 to 1 in the surface and upper part of the subsoil; 0 to 2 in the lower part of the subsoil and in the substratum
Sodicity, SAR - 0 to 1 in the surface and upper part of the subsoil; 0 to 4 in the lower part of the subsoil and in the substratum
A horizon
Value: 4 or 5 dry, 3 or 4 moist
Chroma: 2 or 3 moist, dry or moist
Clay content: 14 to 18 percent
Rock fragments: total range is 35 to 60 percent
35 to 50 percent gravel
0 to 10 percent cobbles
Bt1 horizon
Hue: 5YR or 7.5YR
Value: 4 or 5 dry, 3 or 4 moist
Chroma: 4 or 6, dry or moist
Texture: very gravelly clay loam or gravelly clay loam
Clay content: 35 to 40 percent
Rock fragments: total range is 25 to 55 percent
25 to 45 percent gravel
0 to 10 percent cobbles
Bt2 horizon
Hue: 5YR or 7.5YR
Chroma: 4 or 6, dry or moist
Texture: very gravelly clay loam or very gravelly sandy clay loam
Clay content: 26 to 34 percent
Rock fragments: total range is 35 to 60 percent
35 to 50 percent gravel
0 to 10 percent cobbles
Calcium carbonate equivalent: 0 to 1 percent
Btk horizon
Hue: 5YR or 7.5YR
Value: 5 through 7 dry, 4 or 5 moist
Chroma: 3 through 6, dry or moist
Texture: very gravelly sandy clay loam or very gravelly loam; some pedons have texture of very gravelly clay loam or gravelly loam
Clay content: 24 to 30 percent
Rock fragments: total range is 35 to 60 percent
35 to 50 percent gravel
0 to 10 percent cobbles
Calcium carbonate equivalent: 2 to 15 percent
Bk horizons
Hue: 5YR or 7.5YR
Value: 6 through 8 dry, 5 through 7 moist
Chroma: 2 or 3 dry, 3 or 4 moist
Texture: very gravelly sandy loam, very gravelly loam, or extremely gravelly coarse sandy loam; some pedons have texture of gravelly loam, gravelly sandy loam, or very gravelly coarse sandy loam
Rock fragments: total range is 35 to 70 percent
35 to 55 percent gravel
0 to 15 percent cobbles
Calcium carbonate equivalent: 15 to 45 percent
BCk horizons
Hue: 5YR or 7.5YR
Value: 5 or 6 dry, 4 or 5 moist
Chroma: 3 through 6 dry, 4 or 6 moist
Texture: very gravelly coarse sand, very gravelly loamy coarse sand, or extremely gravelly coarse sand; some pedons have texture of very gravelly loamy sand or very gravelly coarse sandy loam
Rock fragments: total range is 35 to 65 percent
35 to 55 percent gravel
0 to 10 percent cobbles
Calcium carbonate equivalent: 2 to 15 percent
C horizons
Hue: 5YR or 7.5YR
Value: 5 or 6 dry, 4 or 5 moist
Chroma: 3 through 6, dry or moist
Texture: gravelly loamy sand, very gravelly loamy sand, or very gravelly coarse sand; some pedons have texture of gravelly sandy loam
Calcium carbonate equivalent: 0 to 5 percent
Rock fragments: total range is 30 to 55 percent
30 to 45 percent gravel
0 to 10 percent cobbles
Other features: some pedons have texture of silt loam, loam, or very fine sandy loam in residual layers derived from siltstone
COMPETING SERIES: At present, there are no other series in this family.
GEOGRAPHIC SETTING: Pedregal soils are on narrow, beveled summits and on shoulders of erosional fan remnants. They formed in alluvium derived from Precambrian granite, gneiss, and schist over residuum derived from Tertiary granitic sandstone, siltstone, and fanglomerate. Slopes are 2 to 15 percent. Elevation ranges from 5,800 to 7,800 feet. The mean annual precipitation is 13 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 47 to 50 degrees F. The frost-free period is 130 to 160 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Predawn and Portillo soils. Predawn soils are fine-loamy and occur on adjacent summits. Portillo soils are loamy-skeletal, have mollic epipedons, and occur on adjacent backslopes of erosional fan remnants generally below Pedregal soils.
DRAINAGE AND PERMEABILITY: Well drained; high surface runoff; permeability is slow in the upper part and rapid or very rapid in the lower part.
USE AND VEGETATION: Pedregal soils are used for urban development, livestock grazing, and recreation. The historic climax vegetation is twoneedle pinyon, oneseed juniper, ring muhly, and blue grama. The ecological site is Pinus edulis-Juniperus monosperma /Cercocarpus montanus-Chrysothamnus nauseosus/Bouteloua gracilis(F036XB135NM).
DISTRIBUTION AND EXTENT: Pedregal soils are of small extent on the southeastern 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. Pedregal is a street name in Santa Fe.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - The zone from the soil surface to 2 inches. (A horizon)
Argillic horizon - The zone from 2 to 12 inches. (Bt1, Bt2, and Btk horizons)
Calcic horizon - The zone from 12 to 45 inches. (Bk1 and Bk2 horizons)
Paleustalf great group - The upper part of the argillic horizon has 35 to 40 percent clay, and a clay increase of 15 percent or more (absolute) within one inch at its upper boundary. (A and Bt1 horizons)
Particle-size control section - The zone from 2 to 12 inches (Bt1, Bt2, and Btk horizons)
Series control section - The zone from 0 to 60 inches.
Taxonomic version: Classified according to Keys to Soil Taxonomy, Tenth Edition, 2006.