LOCATION HOOKTON CATentative Series
TAXONOMIC CLASS: Fine-loamy, mixed, superactive, mesic Oxyaquic Dystrudepts
TYPICAL PEDON: Hookton clay loam on a slightly convex south facing slope of 2 percent under seeded pasture at 12 meters (40 feet elevation). (Colors are for moist soil unless otherwise stated. When described May 9, 2007, the soil was moist throughout).
Ap--0 to 27 centimeters (0 to 11 inches); black (10YR 2/1) clay loam, very dark grayish brown (10YR 3/2) dry; moderate medium granular and very fine subangular blocky structure; slightly hard, friable, slightly sticky and moderately plastic; many very fine and common fine roots; many very fine and fine irregular pores and common very fine and fine tubular pores; 5 percent gravel; very strongly acid (pH 5.0); clear smooth boundary. (25 to 50 centimeters thick)
AB--27 to 42 centimeters (11 to 17 inches); very dark grayish brown (10YR 3/2) clay loam, pale brown (10YR 6/3) dry; moderate fine subangular blocky structure; slightly hard, friable, moderately sticky and moderately plastic; common very fine and fine roots; common very fine and fine tubular and very fine and fine irregular pores; common fine prominent yellowish brown (10YR 5/6) masses of iron accumulation in the matrix and on surfaces along root channels; 7 percent gravel; very strongly acid (pH 4.6); clear smooth boundary. (0 to 20 centimeters thick)
Bw--42 to 70 centimeters (17 to 28 inches); olive brown (2.5Y 4/3) silty clay loam, light yellowish brown (2.5Y 6/3) dry; moderate fine subangular blocky structure; slightly hard, friable, moderately sticky and moderately plastic; few fine roots; common very fine and fine tubular and very fine and fine irregular pores; common fine prominent strong brown (7.5YR 5/8) masses of iron accumulation in the matrix; 10 percent gravel; very strongly acid (pH 4.6); clear smooth boundary.
Bw--70 to 110 centimeters (28 to 43 inches); dark grayish brown (2.5Y 4/2) clay loam, light brownish gray (2.5Y 6/2) dry; moderate medium subangular blocky structure; slightly hard, friable, moderately sticky and moderately plastic; few fine roots; common very fine and fine tubular and very fine and fine irregular pores; common fine prominent strong brown (7.5YR 5/8) masses of iron accumulation in the matrix; 10 percent gravel; very strongly acid (pH 4.6); clear smooth boundary.
Bw--110 to 130 centimeters (43 to 51 inches); grayish brown (10YR 5/2) clay loam, pale brown (10YR 6/3) dry; weak medium subangular blocky structure; slightly hard, friable, slightly sticky and moderately plastic; common very fine, fine and medium irregular pores; many fine prominent strong brown (7.5YR 5/8) masses of iron accumulation in the matrix; 5 percent gravel; very strongly acid (pH 4.5); clear smooth boundary. (combined thickness of the Bw horizons is 30 to 90 centimeters)
BC--130 to 152 centimeters (51 to 60 inches); brown (10YR 5/3) silty clay loam, pale brown (10YR 6/3) dry; massive; moderately hard, very firm, moderately sticky and very plastic; common very fine irregular pores; many fine prominent strong brown (7.5YR 5/8) masses of iron accumulation and common fine faint light brownish gray (10YR 6/2) iron depletions in the matrix; 3 percent gravel; very strongly acid (pH 4.5). (0 to 25 centimeters thick)
TYPE LOCATION: Del Norte County, California; located approximately 30 meters north of Highway 101; HBLM, USGS Smith River Quadrangle; UTM Zone 10 401899mE 4643893mN; NAD83.
RANGE IN CHARACTERISTICS: The mean annual soil temperature is 12 to 15 degrees C (54 to 59 degrees F). The difference between the mean winter and mean summer soil temperatures varies from 6 to 9 degrees C. The soils are usually moist and are dry for less than 45 consecutive days in all parts between depths of 10 to 30 centimeters (4 and 12 inches) in the four months following the summer solstice.
Umbric epipedon is 25 to 76 centimeters (10 to 30 inches) thick.
Depth to Redoximorphic features: 25 to 50 centimeters (10 to 20 inches)
The particle-size control section (weighted average)
Rock fragments: 0 to 10 percent
Clay content: 27 to 35 percent
A horizon
Hue: 10YR or 2.5Y.
Value: 3 through 5 dry, 2 or 3 moist.
Chroma: 2 or 3 dry and 1 or 2 moist.
Texture of fine earth: clay loam.
Rock fragments: 0 to 10 percent
Clay content: 27 to 32 percent.
Reaction: very strongly or strongly acid.
Bw horizon
Hue: 10YR or 2.5Y.
Value: 5 through 7 dry, 3 through 5 moist.
Chroma: 2 through 6 dry and moist.
Texture of fine earth: silty clay loam or clay loam.
Rock fragments: 0 to 10 percent
Pararock fragments: 0 to 15 percent
Clay content: 27 to 40 percent.
Reaction: very strongly or strongly acid.
Redoximorphic features: fine or medium masses of iron accumulation
Quantity: few, common, or many
Hue: 7.5YR, 10YR, or 2.5Y
Value: 3 through 6
Chroma: 4 through 8
Redoximorphic features: fine or medium iron depletions
Quantity: few, common or many
Value: 3 through 6
Chroma: 1 or 2
Some pedons have Bg or C horizons.
C horizon
Hue: 10YR or 2.5Y.
Value: 5 through 7 dry, 3 through 5 moist.
Chroma: 1 through 4 dry and moist.
Texture of fine earth: silty clay loam, clay loam or silty clay.
Rock fragments: 0 to 10 percent
Pararock fragments: 0 to 15 percent
Clay content: 32 to 45 percent.
Reaction: very strongly or strongly acid.
Redoximorphic features: fine or medium masses of iron accumulation
Quantity: few, common, or many
Hue: 7.5YR, 10YR, or 2.5Y
Value: 3 through 6
Chroma: 4 through 8
Redoximorphic features: fine or medium iron depletions
Quantity: few, common or many
Value: 3 through 6
Chroma: 1 or 2
COMPETING SERIES: This is the Carlotta series. Carlotta soils have redoximorphic features greater than 50 centimeters deep.
GEOGRAPHIC SETTING: Hookton soils are on alluvial fans, eroded fan remnants and dissected terraces. Slopes are 0 to 8 percent. The soils formed in alluvium derived from mixed sources. Elevations are 3 to 43 meters (10 to 141 feet). The climate is humid, characterized by warm wet winters and warm moist summers with fog. A strong marine influence limits the diurnal and annual range of temperature. The mean annual temperature is 11 to 14 degrees C (52 to 57 degrees F). The mean annual precipitation is 1778 to 2286 millimeters (70 to 90 inches). The frost-free period is 270 to 330 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Arcata, Tillas, and Weott soils. Arcata soils have less than 18 percent clay in the particle size control section. Tillas soils do not have redoximorphic features in the upper 100 centimeters. Weott soils have redoximorphic feature within 10 centimeters of the soil surface. Arcata soils are on nearby dissected marine terrace sediments. Tillas soils are on alluvial fans. Weott soils are on floodplains.
DRAINAGE AND SATURATED HYDRAULIC CONDUCTIVITY: Somewhat poorly drained; low runoff; moderately low saturated hydraulic conductivity.
USE AND VEGETATION: The soils are used mainly for pasture. Native vegetation is redwood, grand fir, Sitka spruce, California laurel, red alder, willow, bigleaf maple, and salmonberry.
DISTRIBUTION AND EXTENT: Coastal Redwood Belts; MLRA 4B. The series is of small extent.
MLRA OFFICE RESPONSIBLE: Davis, California
SERIES PROPOSED: Humboldt and Del Norte Counties, California.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
1. Umbric epipedon - the zone from 0 to 27 centimeters.
2. Cambic horizon - the zone from 27 to 130 centimeters.
3. Particle-size control section - the zone from 25 to 100 centimeters, averages 32 percent clay, and 8 percent rock fragments.
ADDITIONAL DATA:
Type location was moved (8/2007) to current location to update the Typical Pedon and Range of Characteristics and to better represent the series concept. The classification was changed at that time to reflect changes in Taxonomy since the series was proposed. The Hookton soils were formally classified as fine-loamy, mixed, superactive, mesic Humic Dystrudepts
OSED scanned by SSQA. Last revised by state on 9/64.
Soil classified using the 10th Edition of the Keys to Soil Taxonomy.