LOCATION EASTPARK CAEstablished Series
TAXONOMIC CLASS: Clayey-skeletal, magnesic, thermic Mollic Haploxeralfs
TYPICAL PEDON: Eastpark clay loam, 0 to 2 percent slopes, rangeland, at an elevation of 1205 feet. (Colors are for dry soil unless otherwise stated.)
A--0 to 7 inches; brown (7.5YR 4/4) clay loam, dark brown (7.5YR 3/4) moist; strong medium subangular blocky structure; hard, friable, slightly sticky and slightly plastic; few very fine and fine roots; common fine interstitial pores; 5 percent gravels; neutral (pH 6.7); clear smooth boundary.
Bt--7 to 15 inches; dark brown (7.5YR 3/4) gravelly clay loam, dark brown (7.5YR 3/4) moist; strong medium subangular blocky structure; hard, very friable, slightly sticky and slightly plastic; few very fine and fine roots; common fine interstitial pores; very few clay films on faces of peds; 15 percent gravels and 5 percent cobbles; neutral (pH 7.0); clear smooth boundary.
BCt--15 to 26 inches; brown (7.5YR 4/4) very gravelly clay, dark brown (7.5YR 3/4) moist; massive; hard, friable, sticky and plastic; few very fine interstitial pores; few clay films on rock fragments; 50 percent peridiotite gravels and 5 percent peridiotite cobbles; neutral (pH 7.2); clear smooth boundary.
C1--26 to 45 inches; light yellowish brown (2.5Y 6/3) extremely gravelly clay loam, olive brown (2.5Y 4/3) moist; massive; slightly hard, very friable, slightly sticky and slightly plastic; few very fine interstitial pores; 65 percent peridiotite gravels and 5 percent peridiotite cobbles; neutral (pH 7.5); abrupt smooth boundary.
C2--45 to 54 inches; light yellowish brown (2.5Y 6/3) loam, light olive brown (2.5Y 5/3) moist; massive; slightly hard, very friable, slightly sticky and slightly plastic; few very fine interstitial pores; 10 percent peridiotite gravels; slightly alkaline (pH 7.5); abrupt smooth boundary.
C3--54 to 60 inches; light yellowish brown (2.5Y 6/3) extremely gravelly sandy clay loam, light olive brown (2.5Y 5/3) moist; massive; slightly hard, very friable, slightly sticky and slightly plastic; few very fine interstitial pores; 60 percent peridiotite gravels; slightly alkaline (pH 7.5).
TYPE LOCATION: Colusa County, California; about 1 mile south and 3/4 mile west of the southern dam of East Park Reservoir; approximately 2150 feet west and 1500 feet south of the northeast corner of Section 9, T. 17 N., R. 6 W., MDB&M; 39 degrees, 20 minutes, 38 seconds north latitude and 122 degrees, 31 minutes, 55 seconds west longitude; USGS Gilmore Peak topographic quadrangle.
RANGE IN CHARACTERISTICS: The mean annual soil temperature is 58 to 63 degrees F. Calcium-Magnesium ratio is less than 1:1 throughout. The soil moisture control section, 5 to 15 inches, is dry in all parts from May 15 to October 31 unless irrigated and is moist in some or all parts from November 1 to May 15. Weighted average clay content of the 7 to 26 inch textural control section ranges from 35 to 50 percent.
The A horizon has dry color of 10YR 5/4, 4/4; 7.5YR 4/4, 3/4 and moist color of 10YR 3/4; 7.5YR 3/4 or 3/3. Texture is clay loam or gravelly clay loam. Coarse fragment content is 0 to 35 percent with 0 to 10 percent cobbles. Reaction is neutral.
The Bt horizon has dry color of 7.5YR 4/4, 4/3, 3/4 and moist color of 7.5YR 3/4 or 3/3. Texture is very gravelly sandy clay loam, very gravelly clay loam, very gravelly clay, extremely gravelly sandy clay loam, extremely gravelly clay loam and extremely gravelly clay.. Coarse fragment content is 35 to 65 percent with 5 to 15 percent cobbles. Reaction is neutral.
The C horizons have dry color of 2.5Y 6/3 and moist color of 2.5Y 5/3 or 4/3. Texture is very gravelly loam, very gravelly sandy clay loam, very gravelly clay loam, extremely gravelly clay loam or extremely gravelly loam, or extremely gravelly sandy clay loam.. Coarse fragment content is 35 to 70 percent with 0 to 10 percent cobbles. Reaction is slightly alkaline.
COMPETING SERIES: There are no competing series in this family.
GEOGRAPHIC SETTING: Eastpark soils are on fan terraces at elevations of 1100 to 1300 feet. The soils formed in alluvium derived from ultrabasic rock on adjacent uplands. The climate has hot dry summers and cool moist winters. Mean annual precipitation varies from 20 to 24 inches. Average January temperature is about 43 degrees F; average July temperature is about 77 degrees F. Mean annual temperature is 58 to 60 degrees F. The frost-free season is 185 to 210 days.
GEOGRAPHICALLY ASSOCIATED SOILS: Corning soils are on higher terraces and have much redder hues. Leesville soils are in a fine-loamy over sandy-skeletal family. Contra Costa soils are on mountain sideslopes and are moderately deep to fine grained sandstone. Henneke and Okiota soils are on adjacent uplands and are moderately deep to ultrabasic bedrock.
DRAINAGE AND PERMEABILITY: Well drained; negligable to medium runoff; slow permeability.
USE AND VEGETATION: The primary use for Eastpark soils is livestock grazing. Native vegetation is annual grasses and forbs with scattered blue oaks.
DISTRIBUTION AND EXTENT: Alluvial fan terraces in the Indian Valley near Stonyford, California. These soils are not extensive. MLRA 14.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California
SERIES PROPOSED: Colusa County, SSA, California, Colusa Soil Survey 1996. Source of name is coined from East Park reservoir.
REMARKS:
Major Diagnostic Horizons:
1. Ochric epipedon: 0 to 7 inches; A
2. Argillic horizon: 7 to 26 inches; Bt, BCt.
3. Clayey-skeletal family: The textural control section, 7 to 26 inches, has an average clay content of 43 percent.
4. Temperature - Moisture (Thermic-Xeric)
4.1 The 5 to 15 inch SMCS is dry in all parts from May 15 to October 31 and is moist in some or all parts from November 1 to May 15.
4.2 The soil temperature is above 47 degrees F. from March 1 to December 15.
4.3 The MAST is 59 to 63 degrees F.
5. Magnesic Family
5.1 Calcium:Magnesium Ratio
Calcium and Magnesium by local Hach kit.
Depth Calcium Magnesium Ca:Mg ratio
(meq/100g) (meq/100g)
0-7" 6 18 0.33
7-15" 7 40 0.17
15-26" 4 40 0.10
26-45" 5 35 0.14
45-54" 4 22 0.18
54-60" 5 23 0.22