LOCATION CHILSON                 AZ

Established Series
Rev. JEJ/RTM/YHH
10/2013

CHILSON SERIES

The Chilson series consists of shallow, well drained, slowly permeable soils that formed from calcareous shale, basalt and fine-grained sandstone. Canoneros soils are on hilly exposures of the Moenkopi formation. Slopes range from 20 to 45 percent. Mean annual precipitation is about 23 inches, and mean annual temperature is about 44 degrees F.

TAXONOMIC CLASS: Clayey, mixed, superactive, frigid Lithic Argiustolls

TYPICAL PEDON: Chilson cobbly clay loam - forest (Colors for dry conditions unless otherwise noted.)

0i--0 to 1 inch; partially decayed pine needles and grass.

A1--1 to 4 inches; dark reddish gray (5YR 4/2) very cobbly clay loam, dark reddish brown (5YR 2/2) moist; weak thick platy breaking to moderate medium granular structure; slightly hard, friable, sticky and plastic; plentiful very fine and fine roots; many micro and very fine interstitial pores; approximately 30 percent basalt and sandstone cobbles and 15 percent gravels by volume; noneffervescent; neutral (pH 7.3); abrupt smooth boundary. (1 to 3 inches thick)

Bt1--4 to 9 inches; reddish gray (5YR 5/2) gravelly clay, dark reddish brown (5YR 2/2) moist; weak fine and medium subangular blocky structure; hard, firm, sticky and plastic; few very fine, fine and medium roots; common very fine and fine tubular and micro and very fine interstitial pores; common thin clay films on ped faces; approximately 30 percent gravel and cobbles by volume; noneffervescent; moderately alkaline (pH 8.0); clear smooth boundary. (5 to 7 inches thick.)

Bt2--9 to 15 inches; reddish brown (2.5YR 4/4) cobbly clay, dark reddish brown (2.5YR 3/4) moist; moderately medium subangular blocky structure; hard, firm, sticky and very plastic; few fine and medium roots; common very fine and fine tubular and micro and very fine interstitial pores; common thin clay films on ped faces and in pores; noneffervescent; moderately alkaline (pH 8.0); abrupt irregular boundary. (6 to 10 inches thick.)

R--15 inches; fractured dark red (2.5YR 3/6) fine grained sandstone and shale bedrock of the Moenkopi formation; extremely hard, extremely firm with some soil material from the horizon above and roots in the fractures; strongly effervescent.

TYPE LOCATION: Coconino County, Arizona. Approximately 50 miles southwest of Winslow, Arizona, in the SW 1/4 of Sec. 13, T14N, R10E. Approximately 500 feet east of Todd Draw near the middle of the slope.

RANGE IN CHARACTERISTICS:

Depth to bedrock: 6 to 20 inches

Reaction: neutral to slightly alkaline

Rock fragments: The soil is generally cobbly, stony and gravelly with the coarse fragment content in the control section of less than 35 percent

Average annual soil temperature: approximately 39 degrees F.

Mean summer soil temperature: approximately 50 degrees F.

Soil moisture: Typic ustic moisture regime

The solum is noneffervescent throughout, although individual fragments of the underlying rock included in the solum may be slightly effervescent.

A horizon
Thickness: 1 to 3 inches
Hue: 5YR, 7.5YR
Value: 3 to 5 dry, 2 and 3 moist
Chroma: 1 and 3, dry or moist
Texture: loam, clay loam

B horizon
Thickness: 8 to 19 inches
Hues: 2.5YR, 5YR, 7.5YR
Values: 3 to 5 dry, 2 and 3 moist
Chroma: 2 to 6, dry or moist
Rock fragments: gravelly or cobbly with less than 35 percent by volume of coarse fragments and has more than 35 percent clay

COMPETING SERIES: This is the Canoneros (NM) series. Canoneros soils formed in eolian 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.

GEOGRAPHIC SETTING: Chilson soils occur on hilly exposures of the Moenkopi formation at elevations ranging from 6,800 to 7,500 feet, under a coniferous forest cover. The soils are formed from calcareous shale, basalt and fine-grained sandstone. The average annual precipitation ranges from 20 to 26 inches, the mean annual air temperature is approximately 44 degrees F. with a mean monthly temperature in January of approximately 28 degrees F. and in July of 57 degrees F. The mean summer temperature of the soil is approximately 50 degrees F. Slopes range from 20 to 45 percent with rock outcrops common on the slopes above 30 percent. Frost-free season is 90 to 110 days.

GEOGRAPHICALLY ASSOCIATED SOILS: Chilson soils occur in the same general area as the Brolliar, McVickers and Hogg soils. All of these soils are over 20 inches to bedrock and lack lithic contact at shallow depths which is characteristic of the Chilson soils.

DRAINAGE AND PERMEABILITY: Well-drained. Runoff is medium and permeability is slow. Infiltration is moderately slow to slow.

USE AND VEGETATION: Used primarily for timber production, wildlife and recreation. Ponderosa pine is dominant with some Gambel oak and alligator juniper present. Some grazing is furnished by the mountain muhly, squirreltail and little blue stem grasses present.

DISTRIBUTION AND EXTENT: These soils have been identified only in the southern portion of Coconino County, Arizona where the Moenkopi formation is exposed at these higher elevations. The series in inextensive with a total of over 2000 acres mapped to date. MLRA 39.

MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Phoenix, Arizona

SERIES ESTABLISHED: Long Valley Area , Coconino County Arizona 1971. Named after nearby stock tank in the area.

REMARKS: Diagnostic horizons and features recognized in this pedon are:

Mollic epipedon - the zone from 1 to 9 inches (A and Bt1 horizons)

Argillic horizon - the zone from 4 to 15 inches (Bt1 and Bt2 horizons)

Lithic contact - the boundary at 15 inches (R horizon)

Classified according to Soil Taxonomy, Second Edition, 1999; Keys to Soil Taxonomy, Eleventh Edition, 2010

Updated for the correlation of Walnut Canyoun National Monument, AZ, 5/2013 CEM

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National Cooperative Soil Survey
U.S.A.