LOCATION OILCREEK CA
Established Series
Rev. SAA/JWH/KP
08/2016
OILCREEK SERIES
The Oilcreek series consists of very deep, well drained soils formed on mountain sideslopes. These soils formed in residuum and colluvium derived from mudstone, sandstone, and siltstone. Slope ranges from 15 to 75 percent. Mean annual precipitation is about 1285 millimeters Mean annual air temperature is about 10 degrees C.
TAXONOMIC CLASS: Fine-silty, mixed, superactive, isomesic Mollic Hapludalfs
TYPICAL PEDON: Oilcreek loam on a northwest facing slope of 35 percent under redwood, sitka Spruce, and tanoak forest with a swordfern, salal, and huckleberry understory. (Colors are for moist soil unless otherwise stated. When described on August 16, 2000, the soil was slightly moist throughout.)
Oi--0 to 5 centimeters; slightly decomposed plant material, clear wavy boundary.
A--5 to 25 centimeters; very dark brown (10YR 2/2) loam, dark grayish brown (10YR 4/2) dry; weak fine subangular blocky structure; very friable, slightly hard, slightly sticky and slightly plastic; common fine, coarse, and many very fine roots throughout; neutral (pH 7.0), clear smooth boundary. (Combined thickness of the A horizon ranges from 18 to 25 centimeters.)
Bt1--25 to 41 centimeters; dark grayish brown (10YR 4/2) loam, light brownish gray (10YR 6/2) dry; moderate medium and fine subangular blocky structure; friable, slightly hard, slightly sticky and slightly plastic; many fine, medium, and coarse roots throughout; 30 percent distinct clay films on all faces of peds; slightly acid (pH 6.5); gradual smooth boundary.
Bt2--41 to 75 centimeters; dark grayish brown (10YR 4/2) clay loam, light brownish gray (10YR 6/2) dry; strong medium subangular blocky structure; firm, moderately hard, slightly sticky and moderately plastic; few fine, medium, and coarse roots throughout; 35 percent distinct clay films on all faces of peds; moderately acid (pH 6.0); gradual wavy boundary.
Bt3--75 to 152 centimeters; brown (10YR 4/3) clay, light brownish gray (10YR 6/2) dry; strong medium subangular blocky structure; firm, moderately hard, slightly sticky and moderately plastic; few fine, medium and coarse roots throughout; 40 percent distinct clay films on all faces of peds; strongly acid (pH 5.5). (Combined thickness of the Bt horizon is 127 to 182 centimeters.)
TYPE LOCATION: Humboldt County, California; located 2.750 kilometers north of Scotia on logging road H03.67; USGS Scotia CA Quadrangle; WGS84 decimal degrees 40.4700300 latitude, -124.0798095 longitude; UTM Zone 10 408462mE, 4480488mN; NAD 83.
RANGE IN CHARACTERISTICS:
Soil moisture: The soil moisture control section is not dry in any part for as long as 90 cumulative days in normal years. The soils have a udic soil moisture regime.
Soil Temperature: The mean annual soil temperature at 50 centimeters (20 inches) is 9 to 12 degrees C (49 to 54 degrees F). The difference between mean summer and mean winter temperature is less than 6 degrees C. The soils have an isomesic soil temperature regime.
Depth to Redoximorphic features: Greater than 100 centimeters.
Particle-Size Control Section (weighted average):
Pararock Fragments: 0 to 5 percent paragravel
Clay content: 24 to 30 percent
A horizon
Hue: 10YR
Value: 2 or 3, 4 or 5 dry
Chroma: 1 or 2, dry or moist
Texture of fine earth: silt loam or loam
Clay content: 18 to 24 percent
Reaction: slightly acid to neutral
Bt horizon
Hue: 10YR
Value: 3 through 5, 4 to 6 dry
Chroma: 2 to 4 moist or dry
Texture of fine earth: loam, clay loam, silty clay loam
Pararock fragments: 0 to 14 percent paragravel
Clay content: 22 to 32 percent
Reaction: moderately to slightly acid
C horizon (when present)
Hue: 10YR or 2.5YR
Value: 4 through 6 moist, 5 or 6 dry
Chroma: 3 or 4, moist or dry
Texture of fine earth: clay loam, silty clay loam
Pararock fragments: 0 to 14 percent paragravel
Clay content: 27 to 34 percent
Reaction: very strongly to slightly acid
COMPETING SERIES: There are no other series in this family.
GEOGRAPHIC SETTING: Oilcreek (T) soils are on mountain slopes. Slopes range from 15 to 75 percent. The soils formed in residuum and colluvium derived from siltstone, mudstone, and sandstone. Elevations are 25 to 520 meters (80 to 1400 feet). The climate is humid, characterized by cool, foggy summers and cool wet winters. Mean precipitation is 1040 to 1530 millimeters (41 to 60 inches). The mean annual air temperature is 9 to 12 degrees C (49 to 54 degrees F). The mean January temperature is about 8 degrees C. The mean July temperature is about 14 degrees C. Frost free season is about 250 to 330 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the
Ferncat (T), and
Sleepyhollow (T) soils. Ferncat soils have redoximorphic features below 50 centimeters. Sleepyhollow soils do not have an increase in clay content of more than 20 percent in the particle size control section. All soils are found on similar positions on mountain slopes and ridges.
DRAINAGE AND SATURATED HYDRAULIC CONDUCTIVITY: Well drained, medium to high runoff, moderately high saturated hydraulic conductivity.
USE AND VEGETATION: The soils are used mainly for timber production, wildlife habitat, and watershed. Natural vegetation includes Sitka spruce, redwood, and Douglas fir with an understory of western swordfern, and salal.
DISTRIBUTION AND EXTENT: Coastal Redwood Belt MLRA 4B. The series is of small extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California.
SERIES ESTABLISHED: Humboldt and Del Norte Counties, California 2016.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
1. Umbric epipedon: the zone from 5 to 25 centimeters. (A horizons)
2. Argilic horizon: the zone from 25 to 152 centimeters. (Bt1, Bt2, Bt3 horizons)
3. Particle size control section: the zone from 25 to 75 centimeters averages 27 percent clay.
ADDITIONAL DATA:
Soils classified by using the 12th edition of the Keys to Soil Taxonomy.
NASIS User Pedon ID 00CA600115
National Cooperative Soil Survey
U.S.A.