LOCATION CURTIN OREstablished Series
TAXONOMIC CLASS: Very-fine, smectitic, mesic Aquic Haploxererts
TYPICAL PEDON: Curtin clay, on a 8 percent slope in a native pasture. When described the soils were moist. (Colors are for moist soil unless otherwise noted.)
A--0 to 5 inches; black (10YR 2/1) clay, very dark gray (10YR 3/1) dry; strong very fine granular and moderate fine subangular blocky structure; very hard, very firm, very sticky and very plastic; many very fine roots; many very fine irregular pores; neutral (pH 6.8); clear smooth boundary. (5 to 9 inches thick)
Bss1--5 to 21 inches; black (10YR 2/1) clay, very dark gray (10YR 3/1) dry; weak coarse prismatic and moderate fine and very fine subangular blocky structure; extremely hard, extremely firm, very sticky and very plastic; common very fine roots; common very fine tubular pores; common pressure faces; few slickensides; neutral (pH 6.8); clear wavy boundary. (15 to 21 inches thick)
Bss2--21 to 37 inches; very dark grayish brown (10YR 3/2) clay, common black (10YR 2/1) tongues, dark grayish brown (10YR 4/2) dry; weak coarse prismatic structure; extremely hard, extremely firm, very sticky and very plastic; few fine roots; common very fine pores; common distinct strong brown (7.5YR 5/6) masses of iron accumulation; many intersecting slickensides; neutral (pH 6.6); gradual wavy boundary. (14 to 20 inches thick)
Bss3--37 to 60 inches; very dark grayish brown (10YR 3/2) clay, dark grayish brown (10YR 4/2) dry; massive; extremely hard, extremely firm, very sticky and very plastic; few fine roots; common very fine tubular pores; common distinct strong brown (7.5YR 5/6) masses of iron accumulation; many intersecting slickensides; neutral (pH 6.6).
TYPE LOCATION: Douglas County, Oregon; 8 miles northeast of Roseburg on the Diamond Lake Highway; 500 feet south and 500 feet east of the northwest corner of section 7, T. 27 S., R. 4 W.
RANGE IN CHARACTERISTICS: The soils are usually moist but have a dry period during the summer. The mean annual soil temperature ranges from 52 to 57 degrees F. The soils have cracks that open for 60 to 80 consecutive days in most years during the summer. Depth to bedrock is commonly 60 inches or more. Rock fragments range from 0 to 15 percent gravel and 0 to 5 percent cobbles. Small (1 to 3 mm) concretions are common throughout the profile in some pedons. The control section is clay with more than 60 percent clay. Slickensides are close enough to intersect in all or part of the control section. Depth to aquic conditions and redox concentrations is 20 to 30 inches.
The A horizon has hue of 10YR or 2.5Y, value of 2 or 3 moist, 3 or 4 dry and chroma of 1 or less moist and dry.
The Bss2 horizon has hue of 10YR, 7.5YR, and 2.5Y, value of 2 or 3 moist, 3 or 4 dry and chroma of 2 through 4 moist and dry.
The Bss3 horizon has hue of 10YR or 2.5Y, value of 3 through 5 moist, 4 through 6 dry and chroma of 2 through 4 moist and dry. Below 40 inches textural stratification is common in some pedons.
COMPETING SERIES: There are no competing series.
GEOGRAPHIC SETTING: Curtin soils are on broad alluvial fans, drainageways and foot slopes at elevations of 400 to 2,000 feet. Slopes are 3 to 20 percent. The soils formed in clayey alluvium and colluvium weathered predominantly from basalt but also volcanic breccia and tuffs. The climate is characterized by warm and dry summers and cool and moist winters. The mean annual precipitation is 30 to 60 inches. The mean annual temperature is 50 to 55 degrees F., average January temperature is about 39 degrees F., and average July temperature is about 66 to 68 degrees F. The frost-free period is 160 to 235 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Bashaw, Climax, Dixonville, and Philomath soils. All of the soils except Bashaw and Climax lack intersecting slickensides. Dixonville and Philomath soils are well drained. Bashaw soils are poorly drained and have chromas of less than 1 throughout the control section. Climax soils are less than 40 inches deep to a paralithic contact.
DRAINAGE AND PERMEABILITY: Somewhat poorly drained; very slow permeability. The apparent water table is at depths of 6 to 18 inches between December and April.
USE AND VEGETATION: These soils are used for livestock grazing and improved pasture. Native vegetation is scattered Oregon white oak, rose, poison oak, grasses and sedges.
DISTRIBUTION AND EXTENT: Umpqua Valleys of west-central Oregon; MLRA 2, 5. The series is inextensive.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California
SERIES ESTABLISHED: Douglas County, Oregon, 1994.
REMARKS: The 1994 draft reflects a change in classification from Chromic Pelloxererts to Aquic Haploxererts.
Diagnostic features recognized in this pedon:
Aquic feature - the zone from 21 to 37 inches (Bss2 horizon) having aquic conditions for some time in most years and prominent redox concentrations with moist chroma of 2.