LOCATION BOBTAIL CO+NMEstablished Series
Typically, Bobtail soils have light brownish gray very friable platy very strongly acid A2 horizons, brown strongly acid gravelly coarse sandy loam B2 horizons, and grayish brown medium acid gravelly coarse sandy loam C horizons over hard bedrock at a depth of 30 inches.
TAXONOMIC CLASS: Coarse-loamy, micaceous Typic Haplocryepts
TYPICAL PEDON: Bobtail gravelly sandy loam - forest. (Colors are for dry soil unless otherwise noted.)
01--2 to 1 inches; undecomposed organic material principally needles, bark, twigs, and the fleshy remains of understory plants.
02--1 to 0 inch; partially decomposed organic material like that of the horizon above. Very strongly acid (pH 4.5).
A2--0 to 4 inches; light brownish gray (10YR 6/2) gravelly coarse sandy loam, grayish brown (10YR 5/2) moist; weak thick platy structure that parts to moderate fine granules; soft, very friable, nonsticky, nonplastic; 20 percent gravel; very strongly acid (pH 4.8); gradual wavy boundary. (2 to 8 inches thick)
B2--4 to 18 inches; brown (10YR 5/3) gravelly coarse sandy loam, dark brown (10YR 4/3) moist; weak medium subangular blocky structure that parts to coarse granules; soft, very friable, nonsticky, nonplastic; 20 percent stones; strongly acid (pH 5.2); gradual wavy boundary. (8 to 28 inches thick)
C--18 to 30 inches; grayish brown (2.5Y 5/2) gravelly coarse sandy loam, dark grayish brown (2.5Y 4/2) moist; massive; soft, very friable, nonsticky, nonplastic; 30 percent gravel; medium acid (pH 6.0); abrupt wavy boundary. (10 to 30 inches thick)
R--30 to 60 inches; hard gneiss and biotite schist bedrock.
TYPE LOCATION: Grand County, Colorado; SE 1/4 of Sec. 10, T. 2 S., R. 76 W.
RANGE IN CHARACTERISTICS: Thin dark colored A1 horizons overlie the albic horizons in some pedons. The soils are noncalcareous throughout with acidity decreasing with increasing depth. Base saturation ranges from 30 to 100 percent with some but not all subhorizons above 30 inches being less than 60 percent base saturated. Depth to the lithic contact ranges from 20 to 40 inches. Depth to the base of the cambic horizon ranges from 10 to 30 inches. The upper part of the control section is typically gravelly coarse sandy loam and the lower part is gravelly coarse sandy loam or gravelly loamy coarse sand. On a weighted average basis the control section is coarse-loamy with the clay ranging from 4 to 18 percent, silt from 5 to 40 percent, and sand from 50 to 82 percent with 15 to 75 percent of the sand fraction being medium, coarse, and very coarse sand. Rock fragments range from 0 to 35 percent in a major part of the solum and any C horizon and are mainly 1/2 to 10 inches in diameter. A majority of subhorizons above the bedrock have hue of 7.5YR or yellower. Mottling above a depth of 30 inches ranges from no mottling to a few faint mottles with the chroma of both matrix and mottles exceeding 2. These soils are dry in some part of the moisture control section at some period of most years.
The A2 horizon has hue of 2.5Y through 7.5YR, value of 5 through 8 dry, 4 through 7 moist, and chroma of 1 through 6. It is strongly or very strongly acid (1:5 dilution unbuffered organic dye).
The B2 horizon has hue of 2.5Y to 5 YR, value of 5 through 7 dry, 4 through 6 moist, and chroma from 1 through 6. It ranges from medium acid to very strongly acid (15 dilution unbuffered organic dye).
The C horizon has hue of 5Y through 7.5YR. It ranges from neutral to strongly acid (1:65 dilution unbuffered organic dye).
COMPETING SERIES: These are the Azwell, Hanks, Jenkins, Jughandle, Lake Janee, Ligget, Ryorp, Sambrito, and Walters series. Azwell soils lack a continuous A2 horizon and are in areas of high winter rainfall. Hanks, Lake Janee, Ligget, Sambrito, and Walters soils lack a lithic contact above a depth of 40 inches. Jenkins soils have only minor amounts of coarse and very coarse sand in the sand fraction. (See Remarks.) Jughandle soils lack continuous A2 horizons and have clayey lamellae below the B2ir horizon. Ryorp soils are slightly to medium acid and are more than 60 percent base saturated in all subhorizons above a depth of 30 inches.
GEOGRAPHIC SETTING: The Bobtail soils are on gently to steeply sloping hills, ridges, and mountain slopes. Slopes typically range from about 2 to 40 percent or more. The soil formed in moderately thin coarse and moderately coarse textured parent material derived from gneiss and schist. At the type location the mean annual precipitation is about 30 inches with peak periods of precipitation in the spring and early summer months. Mean annual temperature is 34 degrees F and mean summer temperature is 38 degrees F.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Darling and Leal soils. Darling soils have a spodic horizon and lack bedrock above a depth of 40 inches. Leal soils are less than 60 percent base saturated in all subhorizons above a depth of 30 inches and lack bedrock above a depth of 40 inches.
DRAINAGE AND PERMEABILITY: Well to somewhat excessively drained; slow to very slow runoff; rapid to very rapid permeability.
USE AND VEGETATION: Use as grazing land, recreation, and for timber production. Native vegetation is spruce, fir, lodgepole pine, vaccinium, and buffaloberry.
DISTRIBUTION AND EXTENT: Mountainous areas of Colorado and Wyoming. The series is of moderate extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana
SERIES ESTABLISHED: Frazer Alpine Area, Grand County, Colorado, 1957.
REMARKS: Differentiation from Jenkins series needs further study. The Jenkins series is not defined in terms of sand size in the 1969 series description. Last updated by the state 4/73.
The mineralogy class was changed from paramicaceous to micaceous in 07/2010 by the National Soil Survey Center on request of the responsible MLRA regional office. The change was necessary based on the eleventh edition of the Keys to Soil Taxonomy, 2010.