LOCATION GAP OREstablished Series
TAXONOMIC CLASS: Ashy over loamy, amorphic over isotic Xeric Vitricryands
TYPICAL PEDON: Gap sandy loam - woodland, on 7 percent east-facing slope at 4330 feet elevation. (When described (7/25/85), the soil was dry throughout. Colors are for moist soil unless otherwise noted)
Oi--4 inches to 0; litter of ponderosa pine needles and twigs.
A1--0 to 4 inches; dark brown (10YR 4/3) sandy loam, yellowish brown (10YR 5/4) dry; weak fine granular structure; slightly hard, friable, nonsticky and nonplastic; many very fine and fine roots; many very fine irregular pores; 5 percent gravel; 18 percent estimated clay; neutral (pH 6.8); clear smooth boundary.
A2--4 to 14 inches; reddish brown (5YR 4/4) sandy loam, brown (7.5YR 5/4) dry; weak medium subangular blocky structure; slightly hard, friable, nonsticky and nonplastic; common fine, medium, and coarse roots; common fine tubular pores; 5 percent gravel; 18 percent estimated clay; neutral (pH 7.0); clear smooth boundary. (Combined thickness of the A horizon is 14 to 20 inches)
2Btb1--14 to 18 inches; reddish brown (5YR 4/4) loam, brown (7.5YR 5/4) dry; moderate medium subangular blocky structure; slightly hard, firm, slightly sticky and slightly plastic; few medium and coarse roots; many very fine tubular pores; few faint clay films in pores; 5 percent gravel and 10 percent soft rock fragments; 22 percent estimated clay; neutral (pH 7.0); clear wavy boundary.
2Btb2--18 to 34 inches; reddish brown (5YR 4/4) clay loam, brown (7.5YR 5/4) dry; strong medium subangular blocky structure; hard, firm, sticky and plastic; few coarse roots; common fine tubular pores; many distinct clay films in pores and on ped faces; 10 percent gravel and 20 percent soft rock fragments; 28 percent estimated clay; neutral (pH 7.0); clear wavy boundary.
2Btb3--34 to 47 inches; dark brown (7.5YR 4/4) clay loam, strong brown (7.5YR 5/6) dry; strong medium subangular blocky structure; very hard, very firm, sticky and plastic; few coarse roots; common fine tubular pores; many distinct clay films in pores and on ped faces; 10 percent gravel and 20 percent soft rock fragments; 30 percent estimated clay; neutral (pH 7.0); clear irregular boundary. (Combined thickness of the 2Btb horizon is 26 to 44 inches)
2Cr--47 inches; weathered tuff.
TYPE LOCATION: Jefferson County, Oregon; on USFS road 1150-750 0.1 miles from the junction with USFS road 1150; southwest quarter of the southwest quarter of section 18, T.12 S, R.10 E. (Latitude 44 degrees, 31 minutes, 28 seconds N, Longitude 121 degrees, 34 minutes, 8 seconds W)
RANGE IN CHARACTERISTICS: The depth to a paralithic contact is 40 to 60 inches. The soil moisture control section is usually moist but is dry in all parts for 45 to 60 consecutive days within the 4 months that follow the summer solstice. The mean annual soil temperature is 41 to 45 degrees F. The mean summer soil temperature is 43 to 47 degrees F. Depth to the buried argillic horizon is 14 to 20 inches.
The Oi horizon is 2 to 4 inches thick except where disturbed.
The A horizon has hue of 5YR, 7.5YR and 10YR, value of 3 or 4 moist, 5 dry and chroma of 3 or 4 moist and 4 to 6 dry. It is sandy loam with 10 to 18 percent field estimated clay and 0 to 10 percent gravel. It has 50 to 80 percent glass and glass coated aggregates.
The 2Btb horizons have hue of 5YR or 7.5YR, value of 4 moist, 4 to 6 dry and chroma of 3 or 4 moist and 3 to 6 dry. It is loam or clay loam with 18 to 35 percent field estimated clay. It has 5 to 10 percent gravel and 10 to 25 percent soft rock fragments.
COMPETING SERIES: These are the Almac, Prairie, and Shanahan series. Almac soils are dry for 60 to 75 consecutive days, have a mean annual soil temperature of 39 to 41 degrees F, and have fine sandy loam or sandy loam textures in the lower part of the particle-size control section. Prairie soils are 20 to 40 inches deep to bedrock. Shanahan soils lack the buried argillic horizon and contain 0 to 5 percent field estimated clay in the ash mantle.
GEOGRAPHIC SETTING: The Gap soils are on mountains at elevations of 4000 to 5000 feet. The soils formed in ash deposits over colluvium and residuum from ash flow tuffs or weathered andesite. The climate is characterized by cold, wet winters and cool, dry summers. The mean annual precipitation is 25 to 35 inches, falling mostly as snow. The mean annual temperature is 40 to 44 degrees F. The frost-free period is 10 to 50 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Glaze and Parrego soils. Glaze soils have 35 to 70 percent rock fragments in the buried argillic horizon. Parrego soils are moderately deep to bedrock and have an ashy surface mantle less than 7 inches thick.
DRAINAGE AND PERMEABILITY: Well-drained; moderately slow permeability.
USE AND VEGETATION: These soils are used for timber production, wildlife habitat, recreation, and watershed. Potential native vegetation is ponderosa pine, Douglas fir, white fir, snowberry, and pinegrass.
DISTRIBUTION AND EXTENT: East slope of the Cascade mountains in central Oregon; MLRA 6. The series is of small extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Portland, Oregon
SERIES ESTABLISHED: Jefferson County (Upper Deschutes River Area), Oregon, 1992.
REMARKS: Diagnostic horizons and feature recognize in this pedon are:
Ochric epipedon
Argillic horizon (buried) - from 14 to 47 inches. (2Btb horizons)
Andic soil properties - the upper 14 inches of the soil meets andic soil properties criteria (2c)
Particle-size control sections - the upper mantle (0-14 inches) has andic soil properties and 15-bar water content of less than 12 (dried), this is based on geographically associated soils. The lower part from 14 to 40 inches does not have andic soil properties and has less than 30 percent glass.