LOCATION SIBANNAC OREstablished Series
TAXONOMIC CLASS: Fine-loamy, mixed, superactive, frigid Cumulic Endoaquolls
TYPICAL PEDON: Sibannac silt loam, on a 1 percent slope in a mountain meadow. (Colors are for moist soil unless otherwise noted.)
A1--0 to 6 inches; black (10YR 2/1) silt loam, dark gray (10YR 4/1) dry; weak very fine granular structure; soft, friable, slightly sticky and slightly plastic; many very fine roots; many very fine pores; moderately acid (pH 5.8); abrupt smooth boundary. (3 to 8 inches thick)
A2--6 to 11 inches; black (10YR 2/1) silty clay loam, very dark
gray (10YR 3/1) dry; moderate fine subangular blocky and moderate fine granular structure; hard, friable, sticky and plastic; few fine and many very fine roots; many very fine pores; moderately acid (pH 6.0); clear smooth boundary. (3 to 7 inches thick)
2Bw1--11 to 27 inches; very dark gray (10YR 3/1) clay loam, dark
gray (10YR 4/1) dry; moderate fine and medium subangular blocky structure; hard, friable, sticky and plastic; many very fine roots; many very fine pores; slightly acid (pH 6.2); gradual smooth boundary. (14 to 20 inches thick)
2Bw2--27 to 32 inches; very dark grayish brown (10YR 3/2) clay
loam, dark grayish brown (10YR 4/2) dry; few fine faint dark brown (7.5YR 4/4) mottles; moderate medium subangular blocky structure; hard, firm, very sticky and very plastic; common very fine roots; few fine tubular and many very fine irregular pores; slightly acid (pH 6.3); gradual smooth boundary. (3 to 7 inches thick)
2C1--32 to 42 inches; very dark grayish brown (10YR 3/2) clay loam, dark grayish brown (10YR 4/2) dry; common fine distinct dark brown and strong brown (7.5YR 4/4, 4/6) mottles; massive; slightly hard, firm, sticky and plastic; few very fine roots; common very fine pores; slightly acid (pH 6.4); clear smooth boundary. (6 to 12 inches thick)
3C2--42 to 60 inches; black (10YR 2/1) clay loam, dark gray (10YR 4/1) dry; massive; slightly hard, firm, sticky and plastic; few very fine roots; common very fine pores; slightly acid (pH 6.4).
TYPE LOCATION: Jackson County, Oregon; about 1.5 miles northwest of Howard Prairie Reservoir, 910 feet east and 2,525 feet north of the southwest corner of sec. 10, T. 38 S., R. 3 E.
RANGE IN CHARACTERISTICS: Depth to bedrock is 60 inches or more. The particle-size control section averages 27 to 35 percent clay and has 15 percent or more fine sand or coarser. The mean annual soil temperature is 42 to 47 degrees F. The mollic epipedon is 24 to 35 inches thick. The organic carbon content decreases irregularly with depth. The soil is saturated to the soil surface from January through June.
The A horizon has value of 2 or 3 moist, 3 or 4 dry, and chroma of 1 or 2 moist and dry.
The B horizon has value of 3 moist and 4 dry, and chroma of 1 or 2 moist and dry. It is clay loam or silty clay loam. It has 27 to 35 percent clay. It is moderately or slightly acid.
The C horizon has value of 2 or 3 moist, 4 dry, and has chroma of 1 or 2 moist and dry. It is clay loam or silty clay loam. It has 27 to 35 percent clay. It is moderately or slightly acid.
COMPETING SERIES: These are the Kovich, Marshbrook, Marshdale, and Welch. Kovich soils have skeletal 2C horizons within a depth of 40 inches; it is slightly acid to neutral in the A horizon and neutral in the 2C horizon; precipitation is 16 to 20 inches. Marshbrook soils are slightly acid to moderately alkaline; precipitation is 16 to 22 inches. Marshdale soils have a regular decrease in organic carbon with depth. Welch soils have a significant component of vitric material in the control section; it is slightly acid to neutral in the A horizon and slightly acid to mildly alkaline in the C horizon; precipitation is 9 to 16 inches.
GEOGRAPHIC SETTING: Sibannac soils are on alluvial flats at elevations of 3,600 to 5,800 feet. Slopes are 0 to 7 percent. The soils formed in alluvium from andesite, breccia and tuffs. The mean annual temperature is 40 to 45 degrees F. The mean annual precipitation is 30 to 40 inches. The frost-free period is less than 100 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Farva, Kanutchan, Pinehurst, Rustlerpeak, and Snowlin soils. Farva soils have ochric epipedons and are loamy-skeletal. Pinehurst soils have an argillic horizon and are well drained. Kanutchan soils are fine. Rustlerpeak soils are skeletal and moderately deep to bedrock. Snowlin soils are well drained.
DRAINAGE AND PERMEABILITY: Poorly drained; very slow too slow runoff; moderately slow permeability. A high water table is present at the surface to a depth of 12 inches from January through June.
USE AND VEGETATION: Sibannac soils are used for grazing, water supply, recreation, and wildlife. Native vegetation dominantly is tufted hairgrass, sedges and redtop.
DISTRIBUTION AND EXTENT: Southern Cascades of southwestern Oregon. The soils are of small extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California
SERIES ESTABLISHED: Jackson County Area, Oregon; 1988.
REMARKS: Diagnostic horizons and features:
Mollic epipedon - the zone from the surface to a depth of 27 inches.