LOCATION PREDAWN NMEstablished Series
TAXONOMIC CLASS: Fine-loamy, mixed, superactive, mesic Aridic Paleustalfs
TYPICAL PEDON: Predawn loam--on the summit of an erosional fan remnant sloping 2 percent to the southeast at 6,780 feet elevation--rangeland. (Colors are for dry soil unless otherwise noted. When described, the soil was moist from 0 to 6 inches and dry below.)
A--0 to 2 inches; brown (7.5YR 5/4) loam, brown (7.5YR 4/3) moist; weak medium 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; 10 percent gravel; neutral (pH 6.8); clear smooth boundary. (2 to 4 inches thick)
BA--2 to 4 inches; brown (7.5YR 5/4) loam, brown (7.5YR 4/4) moist; weak medium subangular blocky structure; soft, very friable, slightly sticky and slightly plastic; few fine and common very fine roots; few very fine tubular pores; 5 percent gravel; neutral (pH 6.8); abrupt smooth boundary. (0 to 3 inches thick)
Bt--4 to 9 inches; reddish brown (5YR 5/4) clay loam, reddish brown (5YR 4/4) moist; moderate fine prismatic structure parting to strong medium angular blocky; hard, firm, moderately sticky and moderately plastic; few medium, few fine, and many very fine roots; few very fine tubular pores; many 0.5 to 1 millimeter wide cracks; many distinct clay films on faces of peds; 5 percent gravel; slightly alkaline (pH 7.8); clear smooth boundary. (4 to 7 inches thick)
Btk1--9 to 14 inches; brown (7.5YR 5/4) clay loam, brown (7.5YR 4/4) moist; weak medium prismatic structure parting to moderate medium subangular blocky; hard, friable, moderately sticky and moderately plastic; few fine and common very fine roots; few fine and few very fine tubular pores; few 0.5 to 1 millimeter wide vertical cracks; few distinct clay films on faces of peds and lining pores and few faint clay films on faces of peds; 10 percent gravel; strongly effervescent, secondary calcium carbonate segregated as common medium and large irregularly shaped coats on faces of peds and on rock fragments; strongly alkaline (pH 8.8); clear smooth boundary. (5 to 9 inches thick)
Btk2--14 to 19 inches; light brown (7.5YR 6/4) clay loam, brown (7.5YR 4/3) moist; moderate coarse subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; few fine and common very fine roots; few fine and common very fine tubular pores; few faint clay films on faces of peds and lining pores; 10 percent gravel; strongly effervescent, secondary calcium carbonate segregated as common fine and medium irregularly shaped coats on faces of peds and on rock fragments; strongly alkaline (pH 8.8); abrupt wavy boundary. (0 to 11 inches thick)
Bk1--19 to 27 inches; pinkish white (7.5YR 8/2) loam, pink (7.5YR 7/3) moist; moderate medium platy structure; soft, very friable, slightly sticky and slightly plastic; few fine and common very fine roots; common very fine irregularly shaped pores; 10 percent gravel; violently effervescent, matrix is impregnated with secondary calcium carbonate; strongly alkaline (pH 8.6); clear smooth boundary. (6 to 14 inches thick)
Bk2--27 to 36 inches; pinkish white (7.5YR 8/2) loam, pink (7.5YR 7/3) moist; moderate medium subangular blocky structure; soft, very friable, slightly sticky and slightly plastic; few fine and common very fine roots; common very fine irregularly shaped pores; 10 percent gravel and 3 percent cobbles; violently effervescent, secondary calcium carbonate segregated as many fine and medium irregularly shaped coats on faces of peds, on rock fragments, and on coarse sand grains; strongly alkaline (pH 8.8); gradual wavy boundary. (0 to 11 inches thick)
BCk1--36 to 52 inches; pinkish gray (7.5YR 7/2) gravelly sandy loam, brown (7.5YR 5/3) moist; weak medium subangular blocky structure; soft, very friable, slightly sticky and nonplastic; 20 percent gravel and 3 percent cobbles; violently effervescent, secondary calcium carbonate segregated as many fine and medium irregularly shaped coats on faces of peds, on rock fragments, and on coarse sand grains; strongly alkaline (pH 8.6); abrupt wavy boundary. (8 to 21 inches thick)
BCk2--52 to 77 inches; light reddish brown (5YR 6/4) very gravelly coarse sand, reddish brown (5YR 5/4) moist; single grain; loose, nonsticky and nonplastic; few very fine roots; 40 percent gravel and 10 percent cobbles; slightly effervescent, secondary calcium carbonate segregated as few fine irregularly shaped coats on rock fragments; moderately alkaline (pH 8.4); clear wavy boundary. (8 to 28 inches thick)
C--77 to 86 inches; pink (7.5YR 7/3) gravelly loamy sand, brown (7.5YR 5/3) moist; massive; hard, firm, nonsticky and nonplastic; 20 percent gravel and 5 percent cobbles; slightly effervescent; moderately alkaline (pH 8.4).
TYPE LOCATION: Santa Fe County, New Mexico; about 2.5 miles north of Agua Fria; 30 feet east and 1,140 feet south of the northwest corner of section 20, T.17N., R.9E.; USGS Agua Fria 7.5 minute topographic quadrangle; Latitude 35 degrees 41 minutes 37.5 seconds North and Longitude 106 degrees 1 minute 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 - 17 to 40 inches
Depth to calcareous material (as visible secondary calcium carbonate) - 8 to 13 inches
Depth to calcic horizon - 17 to 33 inches
Volcanic glass content - trace amounts to 5 percent in the coarse silt and very fine sand fractions
Oxalate extractable Al plus 1/2 Fe: less than 0.20 percent
Lithology of rock fragments: granite, gneiss, and schist
Particle-size control section (weighted averages)
Silicate clay content: 28 to 34 percent
Sand content: 30 to 45 percent
Fine sand or coarser content: 15 to 35 percent
Rock fragment content: 5 to 10 percent gravel
Mica content: 1 to 3 percent (by grain count)
Reaction - neutral in the surface; slightly alkaline in the upper part of the subsoil; strongly alkaline in the lower part of the subsoil and upper part of the substratum; moderately alkaline to strongly alkaline in the lower part of the substratum
A, AE, and BA horizons
Value: 5 or 6 dry, 3 through 5 moist
Chroma: 2 through 4 dry or moist
Clay content: 15 to 20 percent
Other features: When chroma is 2, some pedons have AE horizons which are Albic materials and qualify as Albic horizons
Bt horizon
Hue: 5YR or 7.5YR
Value: 4 or 5 dry, 3 or 4 moist
Chroma: 4 or 6, dry or moist
Texture: clay loam or clay
Clay content: 35 to 42 percent
Btk horizons
Value: 5 through 7 dry, 4 or 5 moist
Chroma: 4 or 6, dry or moist
Texture: clay loam or loam
Clay content: 25 to 30 percent
Rock fragments: 5 to 10 percent gravel
Calcium carbonate equivalent: 3 to 15 percent
Salinity, mmhos/cm: 0 to 2
Sodicity, SAR: 4 to 13
Bk horizons
Value: 6 through 8 dry, 5 through 7 moist
Chroma: 2 through 4 dry, 3 through 6 moist
Texture: loam, sandy loam, or fine sandy loam
Rock fragments: total range is 5 to 15 percent
5 to 10 percent gravel
0 to 5 percent cobbles
Calcium carbonate equivalent: 15 to 50 percent
Salinity, mmhos/cm: 2 to 8
Sodicity, SAR: 4 to 13
Other features: minor amounts of secondary gypsum (up to 1 percent) are present in some pedons
Upper BCk horizon
Value: 6 through 8 dry, 5 through 7 moist
Chroma: 2 through 6, dry or moist
Texture: gravelly sandy loam, gravelly loam, or loam
Rock fragments: total range is 5 to 25 percent
5 to 20 percent gravel
0 to 5 percent cobbles
Calcium carbonate equivalent: 5 to 40 percent
Salinity, mmhos/cm: 2 to 8
Sodicity, SAR: 4 to 13
Other features: minor amounts of secondary gypsum (up to 1 percent) are present in some pedons; weak, discontinuous cementation by secondary silica or up to 10 percent durinodes are present in some pedons below 40 inches.
C and lower BCk horizons
Hue: 5YR or 7.5YR
Value: 6 or 7 dry, 4 through 6 moist
Chroma: 2 through 5, dry or moist
Texture: gravelly sandy loam, very gravelly coarse sand, gravelly loamy sand, loam, and sandy loam.
Rock fragments: total range is 5 to 60 percent, averaging 15 to 40 percent with:
15 to 35 percent gravel
0 to 5 percent cobbles
Calcium carbonate equivalent: 2 to 10 percent
Salinity, mmhos/cm: 0 to 2
Sodicity, SAR: 0 to 4
Other features: some pedons do not have gravelly and sandy subhorizons within 80 inches.
COMPETING SERIES: These are the Dallam, Perico, and Rickmore series. All of these soils do not have an upper Bt horizon with more than 35 percent clay and an abrupt clay increase of 15 percent or more, but they have Bt horizons with bases deeper than 60 inches. In addition, all of these soils are more moist in the spring and early summer and have mean annual soil temperatures between 52 and 58 degrees F.
GEOGRAPHIC SETTING: Predawn soils are on summits of eroded fan remnants. They formed in eolian deposits over alluvium derived from Precambrian granite, gneiss, and schist; and Quaternary loess and volcanic ash. Slopes are 1 to 4 percent. Elevation ranges from 6,100 to 8,000 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 46 to 50 degrees F. The frost-free period is 120 to 160 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Alire, Encantado, and Tanoan soils. Alire soils have upper argillic horizons with less than 35 percent clay, and occur on beveled summits of erosional fan remnants. Encantado soils are sandy-skeletal, have calcic horizons, and occur on shoulders and backslopes of erosional fan remnants. Tanoan soils are coarse-loamy, have calcic horizons, and occur on shoulders and footslopes of erosional fan remnants.
DRAINAGE AND PERMEABILITY: Well drained; medium surface runoff; permeability is slow in the upper part and moderately rapid in the lower part.
USE AND VEGETATION: Predawn soils are used for urban development, livestock grazing, and recreation. The historic climax vegetation is blue grama, black grama, galleta, ring muhly, broom snakeweed. The ecological site is Loamy(R036XB112NM).
DISTRIBUTION AND EXTENT: Predawn 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. The name is coined. The name was changed from Piedawn to Predawn.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - The zone from the soil surface to 4 inches. (A and BA horizons)
Argillic horizon - The zone from 4 to about 19 inches. (Bt, Btk1, and Btk2 horizons)
Calcic horizon - The zone from 19 to about 36 inches. (Bk1 and Bk2 horizons)
Particle-size control section - The zone from 4 to 19 inches (Bt, Btk1, and Btk2 horizons)
Series control section - The zone from 0 to 60 inches.
Paleustalf great group - The upper part of the argillic horizon has 35 to 42 percent clay, and a clay increase of 15 percent or more (absolute) within one inch at its upper boundary. (BA and Bt horizons)
Note: This soil has minor amounts of volcanic glass in the coarse silt and very fine sand fractions. It is assumed that most of the volcanic glass derived from nearby Pleistocene ash eruptions has altered to more stable minerals like chalcedony. In addition, Lincoln lab data from adjacent soils indicates that ammonium oxalate extractable aluminum and iron percentages are very low. It is estimated that Predawn soils have similar values and thus do not have the properties of the andic intergrades.