LOCATION LOS ALAMOS NMEstablished Series
TAXONOMIC CLASS: Ashy over pumiceous or cindery, aniso, glassy, mesic Vitrandic Haplargids
TYPICAL PEDON: Los Alamos fine sandy loam--on a summit of a mesa sloping 4 percent to the east northeast at 6663 feet elevation--rangeland. (Colors are for dry soil unless otherwise noted. When described on May 19, 2005, the soil was dry throughout.)
A1--0 to 3 inches; brown (10YR 5/3) fine sandy loam, dark brown (10YR 3/3) moist; moderate coarse subangular blocky structure; slightly hard, friable, slightly sticky and nonplastic; few medium, common fine, and few very fine roots; many fine vesicular pores, common medium vesicular pores, and common medium tubular pores; 2 percent gravel; slightly alkaline (pH 7.8); clear smooth boundary.
A2--3 to 7 inches; brown (7.5YR 5/4) fine sandy loam, brown (7.5YR 4/4) moist; weak coarse subangular blocky structure parting to moderate medium granular; soft, very friable, slightly sticky and nonplastic; common medium, many fine, and many very fine roots; few fine and few medium vesicular pores; moderately alkaline (pH 8.0); clear smooth boundary. (Combined thickness of A horizons is 2 to 7 inches)
Bt--7 to 17 inches; brown (7.5YR 4/4) clay loam, dark brown (7.5YR 3/4) moist; moderate coarse subangular blocky structure parting to moderate medium granular; slightly hard, friable, moderately sticky and moderately plastic; few medium, many fine, and many very fine roots; few very fine and common fine vesicular pores; many prominent clay films on faces of peds; 2 percent paragravel; moderately alkaline (pH 8.2); gradual smooth boundary. (5 to 11 inches thick)
Btk--17 to 23 inches; brown (7.5YR 5/4) loam, brown (7.5YR 5/4) moist; strong medium subangular blocky structure; slightly hard, friable, moderately sticky and moderately plastic; few medium, common fine, and few very fine roots; few fine and many very fine vesicular pores; many distinct clay films on faces of peds; secondary calcium carbonates segregated as many fine threads lining pores; violently effervescent, 3 percent calcium carbonate equivalent; 5 percent paragravel; strongly alkaline (pH 8.8); clear wavy boundary. (6 to 18 inches thick)
Bk1--23 to 32 inches; light brown (7.5YR 6/4) paragravelly ashy sandy loam, brown (7.5YR 4/4) moist; weak medium subangular blocky structure; soft, very friable, nonsticky and nonplastic; common very fine roots; few medium irregularly shaped pores; 30 percent paragravel; violently effervescent, 1 percent calcium carbonate equivalent; secondary calcium carbonate segregated as few fine irregularly shaped coats on faces of peds; moderately alkaline (pH 8.4); clear wavy boundary. (0 to 31 inches thick)
2Bk2--32 to 39 inches; pumice; massive; hard, very firm; few fine roots; 90 percent paragravel; violently effervescent, secondary calcium carbonate segregated as few fine irregularly shaped coats on rock fragments; strongly alkaline (pH 8.7); clear wavy boundary. (30 to 56 inches thick)
2C--39 to 80 inches; pumice; single grain; loose; 95 percent paragravel; moderately alkaline (pH 8.1). (20 to 66 inches thick)
TYPE LOCATION: Santa Fe County, New Mexico; about 3 3/4 miles northeast of Los Alamos; USGS Puye 7.5 minute topographic quadrangle; Latitude 35 degrees 54 minutes 58.58 seconds North and Longitude 106 degrees 13 minutes 27.49 seconds West, NAD 83.
RANGE IN CHARACTERISTICS:
Soil moisture: The soil moisture control section is intermittently moist in some part from July to October and December to March. The soils are driest in May and June. The soil moisture regime is aridic bordering on ustic.
Mean annual soil temperature: 50 to 52 degrees F
Depth to base of ochric epipedon: 2 to 7 inches
Depth to base of argillic horizon: 14 to 29 inches
Depth to calcareous material (as visible secondary calcium carbonate): 2 to 18 inches
Particle-size control section weighted averages
Upper part
Silicate clay content: 25 to 35 percent
Sand content: 35 to 50 percent
Fine sand or coarser content: 25 to 40 percent
Rock fragment content: 5 to 20 percent paragravels, lithology of fragments is pumice.
Volcanic glass content: 5 to 10 percent in the coarse sand fraction
Al + 1/2 Fe by ammonium oxalate: .01 to .02 percent
Lower part
Silicate clay content: 1 to 4 percent
Sand content: 85 to 95 percent
Fine sand or coarser content: 15 to 25 percent
Pararock fragment content: total range is 90 to 95 percent, mostly paragravel, lithology of fragments is pumice
Volcanic glass content: 75 to 90 percent in the coarse sand fraction
Al + 1/2 Fe by ammonium oxalate: .05 to .1 percent
Salinity, mmhos/cm: 0 to 1
Sodicity, SAR: 0 to 4
A horizons
Hue: 7.5YR or 10YR
Value: 5 or 6 dry, 3 or 4 moist
Chroma: 3 or 4, dry or moist
Gravel: 0 to 10 percent
Paragravel content: 0 to 10 percent
Volcanic glass content: 5 to 10 percent in the coarse silt plus sand fraction
Reaction: slightly alkaline or moderately alkaline
Al + 1/2 Fe by ammonium oxalate: .01 to .02 percent
Bt horizon (where present)
Value: 4 or 6 dry, 3 or 4 moist
Chroma: 3 or 4, dry or moist
Texture: clay loam or paragravelly clay loam
Paragravel content: 0 to 20 percent
Volcanic glass content: 5 to 10 percent in the coarse silt plus sand fraction
Reaction: moderately alkaline or strongly alkaline
Al + 1/2 Fe by ammonium oxalate: .01 to .02 percent
Btk horizon
Value: 5 or 6 dry, 4 or 5 moist
Chroma: 3 or 4, dry or moist
Texture: loam, paragravelly sandy clay loam, or clay loam
Paragravel content: 0 to 30 percent
Calcium carbonate equivalent: 3 to 5 percent
Volcanic glass content: 5 to 10 percent in the coarse sand fraction
Reaction: moderately alkaline or strongly alkaline
Al + 1/2 Fe by ammonium oxalate: .01 to .02 percent
Bk horizon (where present)
Value: 5 to 7 dry, 4 or 6 moist
Chroma: 3 or 4 moist or dry
Texture: paragravelly ashy sandy loam, paragravelly sandy loam, ashy sandy clay loam, or very paragravelly ashy coarse sandy loam.
Paragravel (pumice) content: 0 to 35 percent
Calcium carbonate equivalent: 3 to 5 percent
Reaction: moderately alkaline or strongly alkaline
Volcanic glass content: 60 to 70 percent in the coarse sand fraction
Al + 1/2 Fe by ammonium oxalate: .05 to .1 percent
2Bk and 2C horizons
Paragravel (pumice) content: 90 to 95 percent
Calcium carbonate equivalent: 0 to 1 percent
Volcanic glass content: 80 to 90 percent in the coarse sand fraction
Reaction: moderately alkaline or strongly alkaline
Al + 1/2 Fe by ammonium oxalate: .05 to .1 percent
COMPETING SERIES: There are no competing series.
GEOGRAPHIC SETTING: Los Alamos soils are on summits of mesas. They formed in eolian deposits derived from volcanic ash over residuum weathering from pumice. Slopes are 1 to 5 percent. Elevation ranges from 5,800 to 6,800 feet. The mean annual precipitation is 9 to 12 inches with about 45 percent falling as rain from high-intensity convective thunderstorms between July and September. The mean annual air temperature is 50 to 52 degrees F. The frost-free period is 150 to 170 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Abrojo, Chiminet, Romberg and Zacaton soils. Abrojo soils have a glassy mineralogy class, occur on backslopes of undulating plateaus, canyons, and mesas, and formed in colluvium over residuum derived from volcanic ash and pumice. Chiminet soils are glassy, occur on backslopes of mesas, canyons and undulating plateaus, and formed in eolian material and alluvium derived from volcanic ash, tuff, and pumice. Romberg soils have mixed mineralogy, are on backslopes of hills and formed in alluvium derived from conglomerate. Zacaton soils are glassy, occur on lower north-facing backslopes of mesas, canyons and undulating plateaus, and formed in colluvium over residuum derived from pumice and volcanic ash.
DRAINAGE AND PERMEABILITY: Well drained; medium surface runoff; moderately rapid permeability in the surface, moderately slow to moderately rapid permeability in the subsoil, and very rapid permeability in the substratum.
USE AND VEGETATION: Los Alamos soils are used for livestock grazing and recreation. The historic climax vegetation is blue grama, galleta, ring muhly, black grama, and broom snakeweed. The ecological site is Loamy(R036XB112NM).
DISTRIBUTION AND EXTENT: Los Alamos 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 (Santa Fe Area), New Mexico, 1970. The name is from a local community and county.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon: The zone from 0 to 7 inches. (A1 and A2 horizon)
Argillic horizon: The zone from 7 to 25 inches. (Bt and Btk horizons)
Vitrandic feature - based on high glass content and oxalate values in the Btk horizon (17 to 25 inches)
Secondary carbonates: From 17 to 39 inches (Btk, Bk1, and 2Bk2 horizons)
Lithologic discontinuity: About 32 inches
Aniso feature: Loamy at 7 to 23 inches; ashy at 23 to 32 inches, and pumiceous or cindery at 32 to 40 inches.
The classification was changed from fine-loamy, mixed, superactive, mesic Ustic Haplargids to fine-loamy, mixed, superactive, mesic Ustic Calciargids in 2003. In 2005, the type location was visited and re-described. The 12/2006 revision changes the typical pedon. The classification was also changed to ashy over pumiceous or cindery, aniso, glassy, mesic Vitrandic Haplargids.
Classified according to Soil Taxonomy Tenth Edition, 2006.
ADDITIONAL DATA: Calcium carbonate equivalence was determined using a calcimeter. Volcanic glass contents were estimated based on lab data of similar soils in the area. Acid oxalates were estimated based on lab data of similar soils in the area.