LOCATION MONTILLO NMEstablished Series
TAXONOMIC CLASS: Fine, mixed, superactive, frigid Vertic Argiustolls
TYPICAL PEDON: Montillo very gravelly loam--in a ponderosa pine forestland on southeast facing slope of 7 percent at an elevation of 8,200 feet. (Colors are for dry soils unless otherwise noted.)
A--0 to 3 inches; reddish brown (5YR 4/3), very gravelly loam, dark reddish brown (5YR 3/2) moist; moderate thin and medium platy structure; soft, very friable, nonsticky and slightly plastic; common very fine and fine roots; common fine irregular pores; 25 percent basalt gravel, 10 percent basalt cobbles, and 1 percent basalt stones; noncalcareous; slightly acid (pH 6.4); clear smooth boundary. (2 to 4 inches thick)
Bt1--3 to 8 inches; dark reddish brown (5YR 3/2), silty clay loam, dark reddish brown (5YR 3/2) moist; moderate medium granular structure; hard, firm, sticky and very plastic; many very fine and fine roots; common fine irregular pores; common distinct clay films coating faces of peds; 5 percent basalt gravel and 2 percent basalt cobbles; noncalcareous; neutral (pH 6.6); clear smooth boundary.
Btss1--8 to 15 inches; dark reddish brown (5YR 3/2) silty clay, dark reddish brown (5YR 3/2) moist; moderate fine and medium angular blocky structure; very hard, very firm, sticky and very plastic; common very fine and fine and few medium roots; common fine tubular pores; few slickensides and pressure faces; few cracks greater than 5 mm wide occur from 8 to 27 inches; many prominent clay films coating faces of peds; 5 percent basalt gravel and 5 percent basalt cobbles; noncalcareous; slightly alkaline (pH 7.4); clear smooth boundary.
Btss2--15 to 27 inches; dark reddish brown (5YR 3/4) clay, dark reddish brown (5YR 3/3) moist; strong medium angular blocky structure; very hard, very firm, sticky and very plastic; common very fine and fine and few medium roots; common fine tubular pores; common slickensides and pressure faces; few cracks greater than 5 mm wide occur from 8 to 27 inches; many prominent clay films coating faces of peds; 5 percent basalt gravel; noncalcareous; slightly alkaline (pH 7.4); clear smooth boundary.
2Bt2--27 to 32 inches; reddish brown (5YR 4/3) very gravelly clay, dark reddish brown (5YR 3/3) moist; strong medium subangular blocky structure; very hard, very firm, sticky and very plastic; common very fine and fine roots; common fine tubular pores; many prominent clay films coating faces of peds; 35 percent basalt gravel and 1 percent basalt cobbles; noncalcareous; slightly alkaline (pH 7.6); abrupt irregular boundary. (The combined thickness of the Bt horizons is 20 to 36 inches.)
2R--32 inches; basalt with few thin discontinuous coats of calcium carbonate at the upper contact.
TYPE LOCATION: McKinley County, New Mexico; Marquez Quadrangle; about 2.3 miles northwest of Marquez, New Mexico; 107 degrees 20 minutes 7 seconds west longitude, 35 degrees 20 minutes 5 seconds north latitude.
RANGE IN CHARACTERISTICS:
Soil Moisture: The SMCS is usually moist, in some part, for more than 90 cumulative days from May through October. It is usually dry, in all parts, for less than 90 cumulative days during the same period. It is continuously moist in some part November through April. The period of maximum precipitation is July through October. The soil is driest during May and June. Typic ustic moisture regime.
Soil Temperature: 42 to 47 degrees F
Particle size control section: 40 to 60 percent clay with 0 to 30 percent rock fragments.
Depth to lithic contact: 20 to 40 inches to basalt.
Mollic epipedon thickness: 18 to 38 inches.
Vertic features: Depth to slickensides and pressure faces is 8 to 13 inches; subsurface cracks occur from 5 to 30 inches.
A horizon
Hue: 5YR, 7.5YR, or 10YR
Value: 3 or 4 dry, 2.5 or 3 moist
Chroma: 2 or 3 dry
Rock fragments: 5 to 40 percent total (mostly basalt with some cinders)
5 to 25 percent gravel
0 to 10 percent cobbles
0 to 1 percent stones
Reaction: slightly acid to neutral
Bt horizons
Hue: 5YR or 7.5YR
Value: 3 to 5 dry, 2.5 to 4 moist
Chroma: 2 to 6 dry, 1 to 4 moist
Texture: clay, silty clay, or clay loam or silty clay loam with greater that 35 percent clay
Rock fragments: 0 to 45 percent total range (mostly basalt with some cinders)
0 to 30 percent gravel
0 to 25 percent cobbles
0 to 5 percent stones
(Note: When a Bt horizon has greater than 35 percent rock fragments, it is either too thin or is below the particle size control section, to affect the particle size class.)
Reaction: neutral to slightly alkaline
COMPETING SERIES: This is the Rauster (NM) series. Rauster soils are deep to shale of the Chinle Formation.
GEOGRAPHIC SETTING: The Montillo soils formed in eolian material and slope alluvium over residuum derived from basalt (associated with the Mt. Taylor and Mesa Chivato volcanic fields) and are on lava plateaus and cinder cones. Slopes are 0 to 15 percent. Elevations range from 7,800 to 9,000 feet. The mean annual temperature is 40 to 45 degrees F., and the mean annual precipitation is 16 to 20 inches. The frost free period is 90 to 110 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Amcec and Tsoodzil soils on cinder cones and lava plateaus; the Chivato soils on playas; the Canoneros soils on summits of lava plateaus; and the Seco soils on valley floors. The Amcec, Tsoodzil, Chivato, and Seco soils are all very deep. The Canoneros soils are shallow to a lithic contact with basalt.
DRAINAGE AND PERMEABILITY: Well drained, high to very high runoff, and slow permeability.
USE AND VEGETATION: This series is used for wood products, livestock grazing and wildlife habitat. The present vegetation is ponderosa pine with an understory of pinyon, Gambel oak, Arizona fescue, mountain muhly, bottlebrush squirreltail, and prairie junegrass.
DISTRIBUTION AND EXTENT: West central New Mexico; MLRA 39 LRR-D. This series is of moderate extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Phoenix, Arizona.
SERIES ESTABLISHED: McKinley County Area, New Mexico; McKinley County and Parts of Cibola and San Juan Counties, 2001.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon: The zone from 0 to 32 inches. (A, Bt1, Btss1, Btss2, and 2Bt2 horizons)
Argillic horizon: The zone from 3 to 32 inches. (Bt1, Btss1, Btss2, and 2Bt2 horizons)
Vertic features: The presence of slickensides and pressure faces from 8 to 27 inches and subsurface cracks occurring from 8 to 27 inches.
Lithic contact: 32 inches--basalt (2R horizon)
Mineralogy was changed from smectitic to mixed and superactive cation exchange activity class was added in December 2000.
Classified according to Soil Taxonomy Second Edition, 1999.
ADDITIONAL DATA:
NSSL Sample S93NM-031-001