LOCATION NATHROP CO+NM WYEstablished Series
TAXONOMIC CLASS: Loamy-skeletal, mixed, superactive Ustic Argicryolls
TYPICAL PEDON: Nathrop stony loam - grassland. (Colors are for dry soil unless otherwise noted.)
A--0 to 4 inches; grayish brown (10YR 5/2) stony loam, very dark grayish brown (10YR 3/2) moist; moderate fine granular structure; soft, very friable; 15 percent limestone rock, mostly more than 10 inches in diameter but with some pebbles; neutral (pH 7.2); clear smooth boundary. (3 to 5 inches thick)
BA--4 to 8 inches; grayish brown (10YR 5/2) stony loam, very dark grayish brown (10YR 3/2) moist; weak medium prismatic structure parting to weak medium subangular blocks; slightly hard, very friable; 20 percent limestone rock, mostly more than 10 inches in diameter but with some pebbles; neutral (pH 7.2); clear smooth boundary. (3 to 4 inches thick)
Bt--8 to 15 inches; brown (7.5YR 5/3) very stony clay loam, brown (7.5YR 4/3) moist; weak medium prismatic structure parting to moderate medium subangular blocks; very hard, very friable; many faint clay films on faces of peds; clay films in root channels; faint clay films on the underside of coarse fragments; approximately 40 percent of the horizon is limestone rock more than 10 inches in diameter but with some pebbles; slightly alkaline (pH 7.4); clear smooth boundary. (5 to 14 inches thick)
Bk1--15 to 20 inches; brown (7.5YR 5/3) very stony loam, brown (7.5YR 4/3) moist; weak fine and medium subangular blocky structure; very friable; few clay films on faces of peds; clay films on the underside of some coarse fragments; approximately 50 percent of the horizon is stone, most of which is larger than 10 inches in diameter but with some limestone pebbles; visible secondary calcium carbonate occurring mainly as coatings on the underside of rock fragments or as small concretions; calcareous; moderately alkaline (pH 8.2); smooth boundary. (4 to 7 inches thick)
Bk2--20 to 28 inches; light brownish gray (10YR 6/2) very stony loam, grayish brown (10YR 5/2) moist; massive, slightly hard, friable; approximately 55 percent of the horizon is limestone rock more than 10 inches in diameter but with some limestone pebbles; visible secondary calcium carbonate occurring as concretions in thin seams and streaks, and as coatings on the rock fragments; calcareous; moderately alkaline (pH 8.2); gradual wavy boundary. (5 to 10 inches thick)
R--28 inches; hard limestone bedrock; fractured in places but containing less than 5 percent fine material between the rock fragments.
TYPE LOCATION: Chaffee County, Colorado; NE1/4 of Sec. 33, T. 13 S., R. 77 W.
RANGE IN CHARACTERISTICS: Mean annual soil temperature ranges from 35 to 46 degrees F., and mean summer soil temperature ranges from 40 to 58 degrees F. without an O horizon. The mollic epipedon is 7 to 15 inches thick, the solum is 20 to 33 inches thick, depth to calcareous material is 6 to 23 inches, and depth to the limestone bedrock is 20 to 40 inches. The content of organic carbon in the mollic epipedon ranges from .8 to 2 percent and decreases uniformly with depth. The bulk calcium carbonate equivalent, including fine gravel less than 3 inches in diameter, is 6 to 30 percent in nearly all horizons. Content of coarse fragments is 35 to 70 percent, mostly limestone rock more than 10 inches in diameter but with some limestone gravel.
The A horizon has hue of 10YR or 7.5YR, value of 4 or 5 dry, and 2 or 3 moist, with chroma of 1 through 3. It usually has fine granular primary structure but is subangular blocky in some pedons. It is soft to slightly hard and neutral to slightly alkaline.
The Bt horizon has hue of 10YR through 5YR, value of 4 through 6, and 3 or 4 moist, with chroma of 2 through 4. It usually has prismatic primary structure but is subangular blocky in some pedons. It is typically loam or light clay loam, but clay ranges from 18 to 35 percent, silt from 25 to 55 percent, and sand from 20 to 50 percent, with more than 15 percent but less than 35 percent fine or coarser sand. It is neutral to slightly alkaline. Content of coarse fragments is 35 to 70 percent, mostly limestone rock more than 10 inches in diameter but with some limestone gravel.
The Bk horizon has hue of 2.5Y through 7.5YR. Content of coarse fragments is 35 to 70 percent, mostly limestone rock more than 10 inches in diameter but with some limestone gravel. The Bk horizon contains 6 to 12 percent calcium carbonate equivalent of the fine earth fraction and the bulk equivalent, including fine gravel less than 3 inches in diameter, is 6 to 30 percent.
COMPETING SERIES: These are the Blaine, Bowen, Fornor, Fourmile, Geertsen, Hodden, Hoodle, Lagarita, Libeg, Maciver, Nathale, Norriston, Parkview, Quander, Ratiopeak, Spanpeak, Teeler, and Woodhall. The Blaine and Parkview soils have a paralithic contact at depths of less than 40 inches. Fornor, Fourmile, Geertsen, Hodden, Hoodle, Lagarita, Libeg, Maciver, Norriston, Quander, Ratiopeak, Spanpeak and Teeler soils are more than 40 inches deep. Bowen and Woodhall soils lack consistent k horizons in the solum or above the bedrock. Nathale soils have less than 10 percent stones larger than 10 inches in diameter.
GEOGRAPHIC SETTING: Nathrop soils are on mountainsides and hill crests. Slopes range from 2 to 60 percent. The soil formed in very stony medium textured parent material weathered residually from underlying limestone bedrock. Elevation is 8,500 feet or more. In more northerly latitudes in Wyoming, they are at elevations as low at 5,500 feet. The mean annual precipitation is about 20 inches, with peak periods of precipitation during the spring and early summer months. Mean annual temperature ranges from 33 to 44 degrees F., and mean summer temperature ranges from 44 to 58 degrees F.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Chubbs and Trump soils. Chubbs soils have albic horizons and lack mollic epipedons. Trump soils lack argillic horizons.
DRAINAGE AND PERMEABILITY: Well drained; medium or rapid runoff; moderate permeability.
USE AND VEGETATION: These soils are used principally for native pastureland. Native vegetation consists of ring muhly, mountain fescue, and some blue grama.
DISTRIBUTION AND EXTENT: Present known distribution is limited to mountainous areas of Colorado and Wyoming. The series is of moderate extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana
SERIES ESTABLISHED: Chaffee County, Trout Creek Area, Colorado, 1959.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon from the soil surface to 8 inches (A and AB horizons);
Argillic horizon from 8 to 20 inches (Bt and Bk1 horizons)
Lithic contact at 28 inches (top of R horizon.
The Nathrop soils have a cryic temperature regime and an ustic moisture regime.