LOCATION MITCHTOWN OREstablished Series
TAXONOMIC CLASS: Fine, smectitic, mesic Pachic Palexerolls
TYPICAL PEDON: Mitchtown cobbly loam - rangeland, on a 28 percent slope at an elevation of 2,540 feet. (When described on May 20, 1999, the soil was slightly moist throughout. Colors are for moist soils unless otherwise stated.)
A--0 to 3 inches; very dark brown (10YR 2/2) cobbly loam, dark grayish brown (10YR 4/2) dry; weak fine and medium subangular blocky structure; soft, very friable, slightly sticky and slightly plastic; few fine and common very fine roots; few fine and common very fine tubular pores; 10 percent cobbles and 10 percent gravel; slightly alkaline (pH 7.4); abrupt smooth boundary. (1 to 4 inches thick)
2Bt1--3 to 11 inches; dark brown (7.5YR 3/3) cobbly clay loam, brown (7.5YR 4/3) dry; moderate medium subangular blocky structure; slightly hard, friable, moderately sticky and moderately plastic; few medium, fine, and very fine roots; common very fine tubular pores; many distinct clay films on ped faces; 20 percent cobbles and 10 percent gravel; slightly alkaline (pH 7.5); clear wavy boundary.
2Bt2--11 to 23 inches; dark brown (7.5YR 3/3) gravelly clay loam, brown (7.5YR 5/3) dry; moderate fine and medium subangular blocky structure; hard, firm, moderately sticky and moderately plastic; few coarse, medium, fine, and very fine roots; few fine and common very fine tubular pores; many faint clay films on ped faces; 10 percent cobbles and 15 percent gravel; slightly alkaline (pH 7.8); clear wavy boundary. (Combined thickness of the 2Bt horizons is 12 to 25 inches)
2Bk--23 to 38 inches; brown (10YR 4/3) very cobbly silty clay loam, pale brown (10YR 6/3) dry; moderate medium and coarse subangular blocky structure; slightly hard, friable, very sticky and moderately plastic; few very fine roots; few fine and common very fine tubular pores; strongly effervescent; lime coating all rock fragments; 35 percent cobbles and 15 percent gravel; moderately alkaline (pH 8.0); abrupt wavy boundary. (5 to 17 inches thick)
2R--38 inches; andesite
TYPE LOCATION: Wheeler County, Oregon, located about 6 miles NW of the town of Mitchell; 600 feet south and 2,600 feet west of the NE corner of section 12, T. 11 S., R. 20 E. Latitude - 44 degrees, 38 minutes, 03 seconds; Longitude - 120 degrees, 16 minutes, 23 seconds.
RANGE IN CHARACTERISTICS: The soil moisture control section is dry in all parts for one-half to three-fourths of the time when the soil temperature is above 41 degrees F. (andic). The mean annual soil temperature is 50 to 53 degrees F. Depth to bedrock is 20 to 40 inches. The thickness of the mollic epipedon and the depth to secondary carbonates is 20 to 25 inches.
The A horizon has value of 2 or 3 moist, 4 or 5 dry, and chroma of 2 or 3 moist and dry. It is loam with 10 to 20 percent clay. It has 0 to 15 percent cobbles and 0 to 15 percent gravel.
The 2Bt horizons have hues of 10YR or 7.5YR, value of 2 or 3 moist, 3 to 5 dry, and chroma of 2 or 3 moist and dry. It is clay loam or clay with 35 to 45 percent clay. It has 10 to 20 percent cobbles and 5 to 15 percent gravel.
The 2Bk horizon has value of 4 or 5 moist, 6 or 7 dry, and chroma of 1 to 3 moist and dry. It is loam, clay loam, or silty clay loam with 20 to 40 percent clay. It has 15 to 35 percent cobbles and 15 to 25 percent gravel.
COMPETING SERIES: These are the Patron, Prill, and Ridley series. Prill series lack secondary carbonates and are moderately deep to a paralithic contact. Patron series are very deep to basalt. Ridley series are usually very deep to bedrock.
GEOGRAPHIC SETTING: Mitchtown soils are on north and east facing mountain sideslopes slopes and have slopes of 30 to 60 percent. These soils formed in loess over clayey sediments. Basaltic and andesite bedrock underlies this soil. Elevation is 2,400 to 3,200 feet. The climate is semi-arid with cool, moist winters and hot, dry summers. The mean annual precipitation is 9 to 12 inches, and the mean annual temperature is 48 to 51 degrees F. The frost-free period is 90 to 120 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Barbermill, Meadowridge, and Simas soils. Barbermill soils are shallow to a paralithic contact, lack secondary carbonates, and are found on adjacent south slopes. Meadowridge soils are very deep to bedrock, and fine-loamy. Simas soils are very deep to bedrock and are found on nearby hills which formed in tuffaceous sediments.
DRAINAGE AND PERMEABILITY: Well drained; slow permeability
USE AND VEGETATION: This soil is used for livestock grazing and wildlife habitat. The potential native vegetation is bluebunch wheatgrass, Thurber's needlegrass, Sandberg's bluegrass, and juniper.
DISTRIBUTION AND EXTENT: East-central Oregon, MLRA B-10. This series is not extensive.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Portland, Oregon
SERIES ESTABLISHED: John Day Fossil Beds National Monument, Oregon, 2000.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon - from the surface to 23 inches (A, 2Bt1, and 2Bt2 horizons)
Argillic horizon - 3 to 23 inches (2Bt1 and 2Bt2 horizons)
Secondary carbonates - 23 to 38 inches (2Bk horizon)
Pale feature - clay increase of 23 percent between the A and the 2Bt1 horizons)
Aridic moisture regime
Particle-size control section - 3 to 23 inches (2Bt1 and 2Bt2 horizons)