LOCATION MORTENSON UT+COEstablished Series
TAXONOMIC CLASS: Clayey-skeletal, smectitic Ustic Palecryalfs
TYPICAL PEDON: Mortenson silt loam, rangeland. (Colors are for air-dry soil unless otherwise noted.)
E1--0 to 4 inches; light brownish gray (10YR 6/2) silt loam; dark grayish brown (10YR 4/2) moist; moderate thin platy structure; soft, friable, slightly plastic; few fine and common medium roots; few very fine and fine pores; slightly acid (pH 6.1); clear smooth boundary. (2 to 5 inches thick)
E2--4 to 12 inches; pale brown (10YR 6/3) silt loam; brown (10YR 4/3) moist; massive; soft, friable, slightly sticky and slightly plastic; few fine and common medium roots; common very fine pores; few charcoal bits, 10 percent pebbles and cobbles; slightly acid (pH 6.0); gradual smooth boundary. (6 to 10 inches thick)
E3--23 to 28 inches; very pale brown (10YR 7/3) very stony silt loam; brown (10YR 5/3) moist; massive; slightly hard, friable, slightly plastic; few very fine, common medium, few large roots; common very fine pores; 60 percent rock fragments, mainly cobbles and stones; medium acid (pH 6.0); gradual wavy boundary. (12 to 20 inches thick)
EB--28 to 34 inches; 60 percent E and 40 percent B; the E portion is like the E3 horizon above; the B portion is like the Bt1 horizon described below; gradual wavy boundary. (4 to 8 inches thick)
Bt1--34 to 49 inches; pale brown (10YR 6/3) very stony clay; yellowish brown (10YR 5/4) moist; strong medium angular blocky structure; very hard, very firm, very sticky and very plastic; few fine, few medium roots; common very fine pores; many moderately thick clay films; 60 percent rock fragments, 45 percent is cobbles and stones; slightly acid (pH 6.1); gradual smooth boundary. (6 to 10 inches thick)
Bt2--49 to 60 inches; pale brown (10YR 6/3) very stony clay; brown (10YR 5/3) moist; strong medium angular blocky structure; very hard, very firm, very sticky and very plastic; few fine roots; few fine, common very fine pores; many thin clay films; 50 percent is cobbles, stones, and 10 percent pebbles; slightly acid (pH 6.1).
TYPE LOCATION: Sanpete County, Utah; 6 miles east of Mt. Pleasant in Dry Pole Fork; 2,200 feet north and 400 feet west of SE corner of sec. 15, T. 15 S., R. 5 E.
RANGE IN CHATACTERISTICS: The solum is thicker than 5 feet. Depth to the upper boundary of the Bt horizon is 24 to 40 inches. The mean annual soil temperature at a depth of 20 inches ranges from 41 to 46 degrees F. The mean summer temperature ranges from 50 to 58 degrees F. The soils are usually moist, but are dry in parts of the moisture control section for about 30 days during the summer.
The E horizon has hue of 7.5YR through 2.5Y, value of 6 or 7 dry, 4 through 6 moist, and chroma of 2 or 3. It is silt loam, very stony loam or very fine sandy loam, and has 60 percent pebbles, cobbles, and stones. It is medium acid to neutral.
The Bt horizon has hue of 7.5YR through 2.5Y, value of 6 dry, 4 or 5 moist, and chroma of 3 or 4 dry. It is very stony clay, very cobbly silty clay or extremely cobbly clay and has 35 to 70 percent cobbles and stones. It is slightly acid or neutral.
COMPETING SERIES: There presently are no competing series in the family. Similar soils are the Baird Hollow, Callings, Cluff, Duchesne, Fitzgerald, Loberg, Nutras, Sunshine, Tenrag, Vulcan, Worock and Yourame series. Baird Hollow, Callings and Sunshine soils have mollic epipedons. Cluff, Fitzgerald, and Duchesne soils have dark A horizons 6 to 9 inches thick. Cluff, Callings, Sunshine, Loberg, Nutras and Vulcan soils have the upper boundary of the Bt horizon at depths of less than 24 inches. Duchesne, Tenrag, Worock, and Yourame soils have loamy-skeletal particle-size control sections.
GEOGRAPHIC SETTING: Mortenson soils are on very steep mountainsides at elevations of 5,700 to 9,500 feet. Slopes are 20 to 70 percent. These soils formed in colluvium from sandstone. The climate is moist subhumid and the average annual precipitation ranges from 25 to 35 inches. The mean annual temperature is 43 to 45 degrees F. The mean summer temperature is 53 to 58 degrees F. and the freeze-free period ranges from 70 to 80 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are Pritchett, Skylick and Tingey soils. All of these soils have mollic epipedons. Skylick and Tingey soils lack E horizons.
DRAINAGE AND PERMEABILITY: Well drained; medium runoff; slow permeability.
USE AND VEGETATION: These soils are used for timber production, wildlife, and recreation. Potential vegetation is subalpine fir and Englemann spruce.
DISTRIBUTION AND EXTENT: Mountainous areas in Central Utah. The series is inextensive.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana
SERIES ESTABLISHED: Sanpete Soil Survey Area, Utah, 1971.
REMARKS: The Mortenson soils were formerly classified as Gray Wooded soils.