LOCATION HOWARDSVILLE COEstablished Series
TAXONOMIC CLASS: Sandy-skeletal, mixed Ustic Haplocryepts
TYPICAL PEDON: Howardsville gravelly loam, on a west facing, simple, 1 percent slope in grassland at an elevation of 9,300 feet. (Colors are for dry soil unless otherwise noted.) When described on August 2, 1983 the soil was slightly moist from 0 to 10 inches.
A-- 0 to 2 inches; dark grayish brown (10YR 4/2) gravelly loam, black (10YR 2/1) moist; moderate fine granular structure; soft, friable, nonsticky and nonplastic; 15 percent gravel, 5 percent cobbles; slightly acid (pH 6.2); clear smooth boundary. (2 to 6 inches thick)
Bw--2 to 10 inches; brown (7.5YR 5/4) very gravelly sandy loam, dark brown 7.5YR 3/4) moist; weak fine granular structure, soft, friable, nonsticky and nonplastic; 30 percent gravel, 10 percent cobbles, and 2 percent stones; moderately acid (pH 6.0); clear wavy boundary. (6 to 20 inches thick)
C--10 to 60 inches; light brown (7.5YR 6/4) extremely cobbly loamy sand, dark yellowish brown (10YR 4/4) moist; single grain; loose, nonsticky and nonplastic; 30 percent gravel, 25 percent cobble, and 10 percent stone; moderately acid (pH 5.8).
TYPE LOCATION: San Juan County, Colorado; near Durango and Silverton Narrow Gauge Railroad yard, south of Silverton, located about 1,000 feet east and 300 feet north of the southwest corner of Sec. 17, T. 41 N., R. 7 W.; Silverton USGS quad; lat. 37 degrees 48 minutes 18 seconds N. and long. 107 degrees 39 minutes 46 seconds W., NAD 27
RANGE IN CHARACTERISTICS:
Soil moisture regime: udic; dry in some part of the moisture control section for 45 to 90 cumulative days (ustic udic subclass)
Mean annual soil temperature: 36 to 40 degrees F.
Mean summer soil temperature: 44 to 50 degrees F.
Particle-size control section:
Clay content: 0 to 15 percent, (averages 3 to 12 percent)
Silt content: 0 to 30 percent
Sand content: 70 to 100 percent
Rock fragment content: 35 to 80 percent
A horizon:
Hue: 7.5YR or 10YR
Value: 4 to 6 dry, 2 to 4 moist
Chroma: 1 to 4, dry and moist
Rock fragment content: 15 to 35 percent
Reaction: moderately acid to neutral
Bw horizon:
Hue: 7.5YR or 10YR
Value: 5 or 6 dry, 3 to 5 moist
Chroma: 3 to 6, dry and moist
Rock fragment content: 35 to 65 percent
Base saturation: 60 to 90 percent (estimated)
Reaction: moderately acid to neutral
C horizon:
Hue: 7.5YR or 10YR
Value: 5 or 6 dry, 3 to 5 moist
Chroma: 2 to 4, dry and moist
Texture: LS or S
Rock fragment content: 35 to 80 percent
Base saturation: 60 to 90 percent (estimated)
Reaction: moderately acid to neutral
COMPETING SERIES: There are no competing series at present.
Similar soils that were formerly competitors are the: Alflack, Canlodore, Castlepeak, Chena, Cryomont, Graylock, Mirror Lake, Nataga, Nizina, Obscurity, Pirapeak, Ragamuffin, Stecum, and Studebaker series.
Alflack,
Ragamuffin, and Stecum: are moderately deep to bedrock.
Canlodore: have well developed E horizons.
Castlepeak: have moisture control sections that are dry for significantly longer periods of time when the soil temperature at 20 inches is greater than 41 degrees F.
Chena: have substantial amounts of mica throughout the profile.
Cryomont,
Obscurity, and Studebaker: have ash and pumice in the profile.
Graylock: have Bw horizons, reaction of moderately acid to very strongly acid, base saturation of less then 25 percent, and receives most of precipitation in winter and spring.
Mirror Lake: have reaction of strongly acid or very strongly acid.
Nataga: have a maritime climate and mean annual soil temperature of greater than 40 degrees F.
Nizina: are calcareous and have MAST of 32 to 35 degrees F.
Pirapeak: have particle size control sections with rock fragments dominantly cobbles and stones, and the sand fraction is dominantly coarse sand.
GEOGRAPHIC SETTING:
Parent material: alluvium derived from rhyolite, tuff, and similar volcanic rocks.
Landform: fan remnants and river terraces
Slopes: 1 to 6 percent
Elevation: 8,300 to 10,000 feet
Mean annual air temperature: 35 to 38 degrees F.
Mean annual precipitation: 20 to 30 inches.
Wettest months: July, August, and September.
Driest months: January, May, and June receive the least precipitation.
Frost-free period: 30 to 65 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the
Quazar and
Needleton series.
Quazar soils have mollic epipedons and argillic horizons.
Needleton soils have an argillic horizon, and are loamy-skeletal.
DRAINAGE AND PERMEABILITY: Somewhat excessively drained; low runoff; rapid permeability.
USE AND VEGETATION: These soils are used for recreation and urban development. Native vegetation consists of Arizona fescue, mountain muhly, sheep fescue, needlegrasses, western wheatgrass, prairie Junegrass, and Parry's danthonia.
DISTRIBUTION AND EXTENT: Southwestern Colorado. LRR E, MLRA 48A. This series is of small extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana
SERIES PROPOSED: San Juan County (Animas-Dolores Soil Survey Area), Colorado, 1988.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon: The zone from 0 to 2 inches. (A horizon)
Cambic horizon: The zone from 2 to 10 inches. (Bw horizon)
Particle size control section: The zone from 10 to 40 inches. (part of C horizon)
Keys to Soil Taxonomy: Classified according to the Eighth Edition, 1998
Activity class is presumed based on general trend of other soils in the area.
The 04/2002 revision changes the moisture regime from ustic to udic (to ustic-udic subclass).