LOCATION CHACOAN NMTentative Series
TAXONOMIC CLASS: Coarse-loamy, mixed, superactive, mesic Typic Haplargids
TYPICAL PEDON: Chacoan loamy fine sand--in rangeland on a north-facing slope of about 3 percent at an elevation of 6,460 feet. (Colors are for dry soil unless otherwise noted.)
A--0 to 2 inches; yellowish brown (10YR 5/4) loamy fine sand, dark yellowish brown (10YR 4/4) moist; single grain; loose, nonsticky and nonplastic; few very fine roots; slightly alkaline (pH 7.6); abrupt smooth boundary. (1 to 3 inches thick)
Bt1--2 to 7 inches; yellowish brown (10YR 5/6) fine sandy loam, dark yellowish brown (10YR 4/6) moist; moderate medium and coarse subangular blocky structure; slightly hard, very friable, slightly sticky and slightly plastic; many very fine roots; few very fine irregular pores; few faint clay films on faces of peds and bridging sand grains; 1 percent sandstone gravel; slightly alkaline (pH 7.6); abrupt smooth boundary. (5 to 9 inches thick)
Bt2--7 to 12 inches; yellowish brown (10YR 5/6) fine sandy loam, dark yellowish brown (10YR 4/6) moist; weak coarse prismatic structure; hard, very friable, slightly sticky and slightly plastic; common very fine roots; common very fine irregular pores; few distinct clay films on faces of peds and bridging sand grains; 1 percent sandstone gravel; slightly alkaline (pH 7.6); abrupt smooth boundary. (0 to 6 inches)
Bt3--12 to 19 inches; light yellowish brown (10YR 6/4) fine sandy loam, yellowish brown (10YR 5/4) moist; weak very fine and fine subangular blocky structure; hard, friable, slightly sticky and slightly plastic; few very fine roots; few very fine irregular pores; clay bridging of sand grains; 1 percent gravel; slightly effervescent; moderately alkaline (pH 8.0); abrupt smooth boundary. (0 to 10 inches thick)
Bk--19 to 24 inches; yellowish brown (10YR 5/6) fine sandy loam, dark yellowish brown (10YR 4/6) moist; massive; very hard, friable, slightly sticky and slightly plastic; few very fine roots; 2 percent sandstone gravel; common very fine and fine masses of calcium carbonate; violently effervescent; moderately alkaline (pH 8.2); abrupt smooth boundary. (0 to 8 inches thick)
Cr--24 to 32 inches; soft weathered sandstone (0 to 8 inches thick)
R--32 inches; hard sandstone bedrock
TYPE LOCATION: San Juan County, New Mexico; Pueblo Bonito Quadrangle; about 1.6 miles north of the Chaco Culture National Historic Park Visitor Center; about 1,900 feet west and 2,300 feet south of the northeast corner of sec. 16, T. 21 N., R. 10 W. 36 degrees, 03 minutes, 15 seconds north latitude and 107 degrees, 54 minutes, 25 seconds west longitude.
RANGE IN CHARACTERISTICS:
Soil moisture: The SMCS is usually dry, in all parts, 105 to 160 cumulative days from April through October. It is usually moist, in some part, less than 50 cumulative days during the same period. It is intermittently moist in some part November through March. The period of maximum precipitation is July through October. The soil is driest during April, May, and June. Typic aridic moisture regime.
Soil temperature: 50 to 54 degrees F.
Particle-size control section: 10 to 18 percent clay
Depth to bedrock: 20 to 40 inches to hard sandstone. Some pedons do not have a paralithic contact above the hard lithic contact.
Depth to secondary calcium carbonate: 14 to 35 inches.
Rock fragments: 0 to 5 percent gravel throughout. All fragments are sandstone
A horizon
Hue: 10YR
Value: 5 or 6 dry, 4 or 5 moist
Chroma: 3 or 4 dry and moist
Texture: loamy fine sand and fine sandy loam
Bt horizon
Hue: 10YR
Value: 5 or 6 dry, 4 to 5 moist
Chroma: 4 or 6 dry and moist
Texture: fine sandy loam
Btk and Bk horizons
Hue: 10YR
Value: 5 to 6 dry, 4 to 5 moist
Chroma: 4 or 6 dry and moist
Texture: fine sandy loam, loamy fine sand, or sandy clay loam
Calcium carbonate equivalence: 0 to 5 percent.
COMPETING SERIES: These are the Brinkerhoff (AZ), Delp (NV), Enos (WY), Granshaw (NV), Mayqueen (NM), Shiprock (NM), Wallson (WY), and Woolsey (NV) series. The Brinkerhoff, Delp, Granshaw, Mayqueen, Shiprock, Wallson, and Woolsey soils are all very deep. The Enos soils are moderately deep to shale.
GEOGRAPHIC SETTING:
Parent material: eolian and alluvial materials derived from sandstone
Landform: mesas, cuestas, hills, and ridges.
Slopes: 1 to 8 percent.
Elevation: 6,100 to 6,500 feet.
Mean annual precipitation: 7 to 10 inches.
Mean annual air temperature: 48 to 52 degrees F.
Frost-free period: 100 to 135 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are Benally, Doak, Kimnoli, and Shiprock soils. The Benally, Doak, and Shiprock soils are very deep and on lower landscape positions. The Kimnoli soils are shallow and on mesa summits and cuesta dipslopes.
DRAINAGE AND PERMEABILITY: Somewhat excessively drained; low to medium runoff; moderately rapid permeability.
USE AND VEGETATION: These soils are used for rangeland. Present native vegetation is galleta, blue grama, winterfat, Indian ricegrass, rubber rabbitbrush, fourwing saltbush, prickly pear and yucca.
DISTRIBUTION AND EXTENT: Northwest New Mexico. LRR-D, MLRA 35. This series is of small extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Phoenix, Arizona
SERIES PROPOSED: San Juan County, New Mexico; Chaco Culture National Historical Park, 2001. The name Chacoan is taken from people who once inhabited Chaco National Historical Park.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon: The zone from about 0 to 2 inches. (A horizon)
Argillic horizon: The zone from 2 to 19 inches. (Bt horizons)
Paralithic contact: Soft, somewhat weathered sandstone. (Cr horizon)
Lithic contact: Hard sandstone bedrock at about 32 inches. (R horizon)
Classified according to Soil Taxonomy Second Edition, 1999.