LOCATION TERWILLIGER CA
Established Series
Rev. JJN/TDC
01/2023
TERWILLIGER SERIES
The Terwilliger series consists of moderately deep, well drained soils that formed in material weathered from siltstone. Terwilliger soils are on hills and uplands and have slopes of 2 to 50 percent. The mean annual precipitation is about 15 inches and the mean annual temperature is about 50 degrees F.
TAXONOMIC CLASS: Fine, smectitic, mesic Typic Haploxeralfs
TYPICAL PEDON: Terwilliger stony silty clay loam - on a northeast facing convex slope of 18 percent under Idaho fescue, bluebunch wheatgrass, bottlebrush, squirreltail and buckbrush at 2,760 feet elevation. (Colors are for dry soil unless otherwise stated. When described (7/24/75) the soil was dry above 10 inches and moist below.)
A11--0 to 2 inches; light brownish gray (2.5Y 6/2) stony silty clay loam, dark grayish brown (2.5Y 4/2) moist; weak thick platy structure; hard, friable, sticky and plastic; many very fine and fine roots; common very fine tubular pores; 3 percent stones, 2 percent cobbles and 5 percent pebbles; slightly acid (pH 6.5); abrupt smooth boundary. (0 to 3 inches thick)
A12--2 to 6 inches; light brownish gray (2.5Y 6/2) stony silty clay loam, dark grayish brown (2.5Y 4/2) moist; moderate thick platy structure; very hard, friable, sticky and very plastic; common very fine and fine roots; few very fine tubular pores; 3 percent stones, 2 percent cobbles and 5 percent pebbles; slightly acid (pH 6.5); abrupt smooth boundary. (2 to 8 inches thick)
B1t--6 to 13 inches; pale brown (10YR 6/3) silty clay loam, dark grayish brown (2.5Y 4/2) moist; moderate medium prismatic structure; very hard, firm, very sticky and very plastic; few very fine and fine roots; few very fine tubular pores; many thin clay films on peds and in pores; 1 percent stones, 3 percent cobbles and 5 percent pebbles; neutral (pH 6.8); clear smooth boundary. (4 to 8 inches thick)
B21t--13 to 19 inches; light olive brown (2.5Y 5/4) heavy silty clay loam, dark grayish brown (2.5Y 4/2) moist; strong medium prismatic structure; very hard, very firm, very sticky and very plastic; few very fine and fine roots; few very fine tubular pores; many thin clay films on peds and in pores; 1 percent stones, 2 percent cobbles and 5 percent pebbles; neutral (pH 7.0); abrupt wavy boundary. (4 to 7 inches thick)
B22t--19 to 30 inches; light yellowish brown (2.5Y 6/4) silty clay, olive brown (2.5Y 3/4) faces of peds, moist, and light olive brown (2.5Y 5/4) rubbed, moist; strong coarse prismatic structure; extremely hard, very firm, very sticky, and very plastic; few very fine and fine roots; few very fine tubular pores; continuous pressure faces or thin clay films on peds and in pores; 1 percent cobbles, 5 percent pebbles; neutral (pH 7.3); abrupt wavy boundary. (8 to 12 inches thick)
B3t--30 to 34 inches; olive (5Y 5/4) gravelly silty clay, olive brown (2.5Y 3/4) faces of peds, moist, light olive brown (2.5Y 5/4) rubbed, moist; moderate coarse prismatic structure; extremely hard, very firm, very sticky and very plastic; few very fine and fine roots; few very fine tubular pores; continuous pressure faces or thin and moderately thick clay films on peds and in pores; 20 percent fine and medium siltstone pebbles; moderately alkaline (pH 8.0); abrupt wavy boundary. (1 to 6 inches thick)
Cr--34 to 36 inches; weathered, massive siltstone.
TYPE LOCATION: Siskiyou County, California; about 7 miles northeast of Montague, California on the northeast footslope of Mary Peak; about 450 feet south and 100 feet east of the center or 2,190 feet north and 2,540 feet west of sec. 19, T.46N., R.5W.
RANGE IN CHARACTERISTICS: The soil is 20 to 40 inches deep to a paralithic contact of soft massive or laminar, weathered siltstone. The mean annual soil temperature is 51 degrees to 58 degrees F.; the mean January soil temperature is 35 degrees to 39 degrees F.; and the mean July soil temperature is 64 degrees to 79 degrees F. from March 1 to January 1 and exceeds 47 degrees F. from March 25 to November 25. The soil is dry fn most years between the depths of 4 and 12 inches from mid-July through mid-October and is moist in some or all parts the rest of the year. Rock fragments range from O to 35 percent throughout the solum and are mostly gravel. The A horizon is olive gray, olive, light olive gray, pale olive, grayish brown or light brownish gray (5Y 5/2, 5/3, 6/2, 6/3; 2.5Y 5/2, 6/2). Moist colors are dark grayish brown, olive gray, or olive (2.5Y 4/2; 5Y 4/2, 4/3). It is silt loam or silty clay loam and most pedons are stony.
This horizon has 20 to 35 percent clay. It has less than 1 percent organic matter. It is slightly acid or neutral.
The B2t horizon ranges from grayish brown to pale olive (10YR and 5Y 5/2, 5/3, 5/4, 6/2, 6/3, 6/4; 2.5Y 5/2, 5/4, 6/2, 6/4). Moist colors range from very dark grayish brown to olive (lOYR 3/2, 3/3, 3/4, 4/2, 4/3, 4/4; 215Y 3/2, 3/4, 4/2, 4/4, 5/4; 5Y 3/2, 4/2, 4/3, 4/4). It is silty clay loam or silty clay with 27 to 50 percent clay but the top 20 inches of the argillic horizon averages 35 to 50 percent clay. There is at least 6 percent increase in clay from the A horizon to the B2t horizon. When dry, cracks 1/8 to 1/2 inch wide occur but do not continue to the soil surface. Very few to many, fine to large slickensides are in the lower part of the B2t horizon. It is neutral to mildly alkaline.
The B3t horizon has similar color ranges as the B2t horizon, but has rock fragments in amounts of 15 to 35 percent. It is neutral to moderately alkaline.
The Cr horizon has hue of 5Y or 2.5Y.
COMPETING SERIES: These are the Addy (T) and
Hodgson series in other families. Addy and Hodgson soils have an A2 horizon, are more than 40 inches deep, and have mixed mineralogy.
GEOGRAPHIC SETTING: Terwilliger soils are on hills and uplands. Slopes are 2 to 50 percent. The soils forms in colluvium and materials weathered from siltstone of the Hornbrook formation that have a large amount of argillaceous sediment. Rock fragments consisting mostly of cobbles and stones occupy O to 10 percent of the soil surface. Elevations are 2,200 to 3,500 feet. The climate is continental and sub-humid with warm dry summers and cold moist winters. Mean annual precipitation is 12 to 18 inches. Seasonal snowfall is 8 to 36 inches. Mean January temperature is 32 degrees to 36 degrees F.; mean July temperature is 67 degrees to 70 degrees F.; mean annual temperature is 48 degrees to 52 degrees F. Frost-free season is 100 to 140 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the
Duzel,
Hilt,
Kuck,
Lassen,
Mary, and
Salisbury soils. Duzel soils have a mollic epipedon and a fine-loamy control section. Hilt and Mary soils have a fine-loamy control section. Kuck soils have a mollic epipedon and cracks that extend to the soil surface. Lassen soils have clay texture, slickensides that intersect, and wide cracks that extend to the surface. Salisbury soils have a duripan at depths of 20 to 40 inches and hue of lOYR or 7.5YR.
DRAINAGE AND PERMEABILITY: Well drained; medium or rapid runoff; very slow permeability.
USE AND VEGETATION: Used mainly as rangeland. Some areas are cultivated and are used for small grain and pasture, both irrigated and dryland. Native vegetation is bluebunch wheatgrass, Idaho fescue, Sandberg bluegrass, buckbrush and needlegrass.
DISTRIBUTION AND EXTENT: North-central California. Terwilliger soils are of small extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California
SERIES ESTABLISHED: Siskiyou County, California, 1978.
OSED scanned by SSQA. Last revised by state on 10/78.
National Cooperative Soil Survey
U.S.A.