LOCATION TRIANGLE CAEstablished Series
TAXONOMIC CLASS: Fine, smectitic, thermic Sodic Epiaquerts
TYPICAL PEDON: Triangle clay - on a smooth slope of less than 2 percent under spikerush, joint grass, and other wetland grasses and forbs at 80 feet elevation. (Colors are for dry soil unless otherwise stated. When described on April 28, 1976, the soil was dry above 7 inches and moist below).
A--0 to 1 inch; olive gray (5Y 5/2) clay, olive gray (5Y 4/2) moist; strong coarse platy structure; cracks 3 cm wide; extremely hard, friable, very sticky and plastic; few very fine roots; common very fine tubular pores; strongly effervescent with disseminated lime; moderately alkaline (pH 8.0); abrupt smooth boundary. (1/2 to 2 inches thick)
Ag1--1 to 7 inches; dark gray (5Y 4/1) clay, dark olive gray (5Y 3/2) moist; many medium prominent olive and light gray (5Y 5/3, 7/2) mottles, many medium prominent olive and light gray (5Y 4/3, 7/1) mottles moist; strong very coarse and coarse prismatic structure; cracks 3 cm wide; extremely hard, friable, sticky and plastic; common very fine roots; common very fine tubular and interstitial pores; strongly effervescent with disseminated lime and segregated as fine soft masses; moderately alkaline (pH 8.1); clear smooth boundary. (4 to 10 inches thick)
Ag2--7 to 15 inches; olive gray (5Y 5/2) clay, dark olive gray (5Y 3/2) moist; many medium prominent olive and light gray (5Y 5/3, 7/2) mottles, many medium prominent black, dark olive gray and light gray (5Y 2/1, 3/2, 7/2) mottles moist; strong very coarse prismatic structure; intersecting slickensides intersecting peds at 20 degrees to horizontal axis; cracks 2 cm wide; extremely hard, friable, sticky and very plastic; common very fine roots; common very fine tubular and interstitial pores; strongly effervescent with disseminated lime and segregated as fine soft masses; ESP is 4; moderately alkaline (pH 8.2); clear smooth boundary. (4 to 10 inches thick)
Ag3--15 to 34 inches; olive gray (5Y 5/2) clay, dark olive gray (5Y 3/2) moist; many medium distinct black (5Y 2/2) mottles moist; strong very coarse prismatic structure; sphenoids at 35 degrees to horizontal axis; cracks 1.5 cm wide; extremely hard, firm, sticky and very plastic; few very fine roots; common very fine tubular and interstitial pores; strongly effervescent with disseminated lime; moderately alkaline (pH 8.2); clear smooth boundary. (10 to 19 inches thick)
Cgn--34 to 42 inches; pale yellow (2.5Y 7/4) clay loam, olive (5Y 4/3) moist; many fine prominent yellowish brown (10YR 5/6) mottles, many medium prominent yellowish brown and olive (10YR 5/6; 5Y 5/8) mottles moist; weak medium subangular blocky structure; very hard, friable, sticky and plastic; few very fine tubular and common very fine interstitial pores; violently effervescent with disseminated lime; ESP is 32; strongly alkaline (pH 8.8); clear smooth boundary. (6 to 10 inches thick)
Cn1--42 to 61 inches; very pale brown (10YR 7/3) clay loam, olive (5Y 5/6) moist; common medium prominent yellowish brown (10YR 5/8) mottles moist; massive; very hard, friable, sticky and very plastic; few very fine tubular and common very fine interstitial pores; violently effervescent with disseminated lime; ESP is 24; very strongly alkaline (pH 9.0); abrupt smooth boundary. (12 to 20 inches thick)
2Cn2--61 to 70 inches; very pale brown (10YR 7/3) clay loam, olive (5Y 4/3) moist; many fine prominent yellowish brown and dark brown (10YR 3/3, 5/6) mottles moist; massive; 10 percent weakly cemented durinodes 5 to 15 mm in diameter; extremely hard, firm, sticky and plastic; violently effervescent with disseminated lime; very strongly alkaline (pH 9.2).
TYPE LOCATION: Merced County, California; 8 miles northwest of the city of Los Banos; 2,100 feet west of Santa Fe Grade and the Ingomar Duck Club clubhouse, 660 feet east and 50 feet south of the NW corner sec. 8, T. 9 S., R. 10 E.
RANGE IN CHARACTERISTICS: Most years the entire profile is saturated from September through April by a water table and stagnant surface water. Cracks range from 2 to 8 cm wide at the surface and 1 to 2 cm at depths of 34 inches from May 1 to September 15. The depth from the surface to the unrelated lower C horizon ranges from 45 to 70 inches.
The A + Ag1 horizon is 20 to 37 inches thick. It has 40 to 60 percent clay content. Intersecting slickensides and sphenoids are present in all horizons except the A. Some profiles do not have effervescence in the A and Ag1. It is 5Y 4/1, 5/1, 5/2; 2.5Y 5/2; 10YR 4/1; or N 3/0. Moist colors are 5Y 3/1, 3/2, 4/1, 4/2; 2.5Y 4/2; 10YR 3/1 or 4/1. Some pedons have iron manganese shot concretions. Some areas have a 1/8 inch thick white salt crust. Electrical conductivity ranges from 1 to 8 mmhos/cm. ESP ranges from 1 to 27. Reaction is moderately alkaline or strongly alkaline.
The upper C horizon Cgn and Cn1 is 5Y 6/2, 6/3, 7/2, 7/3; 2.5Y 6/2, 7/2, 7/4; 10YR 5/2 or 7/3. Moist colors are 5Y 4/3, 4/4, 5/2, 5/3, 5/6, 5/8; 2.5Y 4/2, 4/4; or 10YR 3/3. It is heavy clay loam or clay with more than 35 to 60 percent clay content. It is massive or has weak subangular blocky structure throughout. It is slightly to violently effervescent. Electrical conductivity ranges from 8 to 16 mmhos/cm. ESP ranges from 15 to 50. Reaction is moderately alkaline or strongly alkaline.
The lower C horizon 2Cn2 is 5Y 5/2, 5/3, 6/3, 7/3; 2.5Y 6/2, 7/2, 7/4 or 10YR 7/3. Moist colors are 5Y 3/2, 4/3, 5/2 or 5/3. It is loam, clay loam, silty clay loam, clay or silty clay with clay content ranging from 22 to 60 percent. There is 1 to 20 percent weakly cemented durinodes 2 to 20 mm in diameter. It is slightly to voilently effervescent. Electrical conductivity is greater than 16 mmhos/cm; ESP ranges from 5 to 30. Reaction is moderately alkaline to very strongly alkaline. This horizon is stratified in some pedons.
COMPETING SERIES: These are the Oswald (T) series in the same family and the Dospalos, Santanela, Turlock, and Willows series in other families. Dospalos soils have a cambic horizon, are not ponded for six months and have less than 15 percent exchangeable sodium. Oswald soils are 20 to 40 inches deep to siltstone. Santanela and Turlock soils have a fine-loamy control section and a natric horizon. Willows soils have a xeric moisture regime and are not ponded for six months.
GEOGRAPHIC SETTING: Triangle soils are in the basin rim and very low alluvial fans of valleys. Slopes are 0 to 2 percent. The soils have formed in mixed alluvium derived from granitic and sedimentary rocks. Most of the areas are flat smooth ponds or basins. Elevations are 70 to 120 feet. The climate is semiarid with hot dry summers and cool moist winters. The mean annual precipitation is about 11 inches. The mean annual temperature is about 62 degrees F. Frost-free season is 210 to 280 days.
GEOGRAPHICALLY ASSOCIATED SOILS; These are the competing Dospalos, Santanela, Turlock soils and the Edminster, and Kesterson soils. Edminster and Kesterson soils are fine-loamy, are not ponded for six momths, and have natric horizons.
DRAINAGE AND PERMEABILITY: Very poorly drained. Ponded 1 to 1 1/2 feet deep from September through April; very slow permeability.
USE AND VEGETATION: These soils are ponded and used for waterfowl hunting with some areas used for limited grazing (during spring and summer) between hunting seasons. The vegetation is swampgrass, Baltic rush, alkali bullrush, sour clover, and other salt tolerant wetland grasses and forbs.
DISTRIBUTION AND EXTENT: These soils are distributed along the basin rim of the central part of the San Joaqin Valley in California. They are not extensive.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California
SERIES ESTABLISHED: Merced County, California, 1979.
REMARKS: These soils were formerly included with and surveyed as the Willows series in the Los Banos Area, series 1939 report. They are being differentiated by characteristics that show a reducing environment (Aquic Moisture Regime) and by being ponded for six months which is not characteristic of the Willows series. ESP determined by versinate method. pH determined by colorimetric method using Thymol Blue and Hellige-Truog Triplex indicatiors. Texture determined by modified Bouyoucos method.