LOCATION CUNNIFF OREstablished Series
TAXONOMIC CLASS: Fine, mixed, superactive, isomesic Typic Palehumults
TYPICAL PEDON: Cunniff silty clay loam - woodland, on an 18 percent southwest-facing slope at 280 feet elevation. (When described on August 29, 1990, the soil was dry to a depth of 6 inches and moist below this depth. Colors are for moist soil unless otherwise noted.)
Oi--2 inches to 0; partially decomposed needles, leaves, twigs, and woody materials.
A1--0 to 6 inches; dark brown (7.5YR 3/2) silty clay loam, brown (10YR 5/2) dry; moderate fine and very fine subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; many very fine, fine, and common medium roots; many fine and very fine tubular pores; 10 percent gravel; strongly acid (pH 5.2); clear smooth boundary.
A2--6 to 12 inches; dark brown (7.5YR 3/3) silty clay loam, brown (7.5YR 5/3) dry; moderate fine subangular blocky structure; slightly hard, firm, slightly sticky and slightly plastic; many very fine, fine, and common medium roots; many fine and very fine tubular pores; 10 percent gravel; strongly acid (pH 5.2); gradual smooth boundary. (Combined thickness of the A horizon ranges from 10 to 16 inches)
Bt1--12 to 43 inches; dark reddish brown (5YR 3/4) silty clay, reddish yellow (7.5YR 6/6) dry; moderate fine and medium subangular blocky structure; hard, very firm, sticky and plastic; few very fine and fine roots; many very fine tubular pores; common distinct clay films on ped faces, many distinct clay films in pores; 5 percent gravel; strongly acid (pH 5.1); clear smooth boundary.
Bt2--43 to 65 inches; dark reddish brown (5YR 3/4) silty clay, reddish yellow (7.5YR 6/6) dry; moderate medium subangular blocky structure; hard, very firm, sticky and plastic; few fine and very fine roots; many very fine tubular pores; many distinct clay films on ped faces and in pores; 5 percent gravel; strongly acid (pH 5.1); gradual smooth boundary. (Combined thickness of the Bt horizon ranges from 35 to 55 inches)
C--65 to 72 inches; brown (7.5YR 5/4) silty clay loam, reddish yellow (7.5YR 7/6) dry; massive; slightly hard, firm, slightly sticky and slightly plastic; common very fine tubular pores; 5 percent gravel; very strongly acid (pH 4.9).
TYPE LOCATION: Curry County, Oregon; located about 2,950 feet south and 1,000 feet east of the northwest corner of section 33, T. 35 S., R. 13 W.; W.M. (Latitude 42 degrees, 30 minutes, 06 seconds N.; Longitude 124 degrees, 15 minutes, 25 seconds W.)
RANGE IN CHARACTERISTICS: The mean annual soil temperature is 51 to 54 degrees F. The difference between mean summer and mean winter soil temperature varies from 5 to 9 degrees F. The soils are usually moist and are dry for less than 45 consecutive days in all parts between depths of 4 and 12 inches in the four months following the summer solstice. The particle-size control section contains 35 to 45 percent clay, 0 to 10 percent gravel, and 0 to 30 percent soft rock fragments. The fragments are weathered sandstone or siltstone and can be crushed. Depth to bedrock is greater than 60 inches. The umbric epipedon is 10 to 16 inches thick. The profile is very strongly acid or strongly acid throughout.
The A horizon has hue of 7.5YR or 10YR, value of 2 or 3 moist, 4 or 5 dry and chroma of 2 or 3 moist and 2 to 4 dry. It is silty clay loam averaging 27 to 35 percent clay. It has 0 to 10 percent gravel and 0 to 10 percent soft rock fragments. Organic matter is 5 to 8 percent.
The Bt horizon has hue of 5YR or 7.5YR, value of 3 to 6 moist, 5 or 6 dry and chroma of 4 to 6 moist and dry. It is silty clay loam, clay loam or silty clay averaging 35 to 45 percent clay. It has 0 to 10 percent gravel and 0 to 30 percent soft rock fragments. Organic matter is 2 to 5 percent.
The C horizon has hue of 5YR or 7.5YR, value of 5 or 6 moist, 6 or 7 dry and chroma of 4 to 6 moist and dry. It is gravelly silty clay loam, silty clay loam, or clay loam averaging 30 to 40 percent clay. It has 0 to 20 percent gravel and 0 to 30 percent soft rock fragments.
COMPETING SERIES: These are the Bentilla, Desons, and Klooqueh soils. Bentilla soils have redox depletions with chromas of 2 or less at depths of 22 to 30 inches and are moderately well drained. Desons soils have an ochric epipedon and greater than 15 percent channer shaped rock fragments in the particle-size control section. Klooqueh soils have mean annual soil temperature greater than 54 degrees F.
GEOGRAPHIC SETTING: Cunniff soils are on broad tops and side slopes of dissected high marine terraces and remnant high stream terraces. Slopes are 0 to 30 percent. The soils formed in marine sediments or alluvium from mixed sources. Elevation is 200 to 600 feet. The climate is humid, characterized by cool wet winters and cool moist summers with fog. A strong marine influence limits the diurnal and annual range of temperature. The mean annual precipitation is 70 to 90 inches. The mean annual temperature is 50 to 53 degrees F. The frost-free period is 210 to 300 days. Cunniff soils are on the Seven Devils geomorphic surface (marine terrace position) or the equivalent Dolph geomorphic surface (high terrace position).
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Burnthill, Cashner, Horseprairie, and Joeney soils. Burnthill and Cashner soils are on adjacent higher marine terraces. Burnthill soils are fine-loamy. Cashner soils have a spodic horizon, 20 to 40 inches deep to an ortstein layer, and are somewhat poorly drained. Horseprairie soils are on adjacent lower marine terraces, are fine-loamy, have a cambic horizon, and an umbric epipedon 20 to 40 inches thick. Joeney soils are on marine terraces, have a spodic horizon, 10 to 20 inches deep to an ortstein layer, and are poorly drained.
DRAINAGE AND PERMEABILITY: Well drained; slow permeability.
USE AND VEGETATION: These soils are used for homesite development, timber production, pasture, watershed, recreation, and wildlife habitat. Native vegetation is Sitka spruce, Douglas fir, grand fir, red alder, tanoak, red elderberry, salmonberry, evergreen huckleberry, salal, western swordfern, evergreen violet, and sweetscented bedstraw.
DISTRIBUTION AND EXTENT: Pleistocene marine terraces in southwestern Oregon; MLRA 1. The series is not extensive.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Portland, Oregon
SERIES ESTABLISHED: Curry County, Oregon, 1995. The source of the name is Cunniff Creek near Gold Beach, Oregon.
REMARKS: Diagnostic horizons and features recognized in this pedon include:
Umbric epipedon - from the surface to a depth of 12 inches (A1, A2 horizons).
Argillic horizon - from a depth of 12 to 65 inches (Bt1, Bt2 horizons).
Humults suborder - the soil has 1.25 percent organic matter in the upper 6 inches of the argillic horizon (Bt1 horizon) and 23.3 kilograms per square meter of organic carbon to a depth of 40 inches.
Pale feature - clay distribution in the argillic horizon does not decrease from its maximum amount by 20 percent or more within a depth of 60 inches from the soil surface (Bt1, Bt2 horizons).
Particle-size control section - from 12 to 32 inches (part of the Bt1 horizon).