LOCATION DREXEL MTEstablished Series
TAXONOMIC CLASS: Loamy-skeletal, mixed, superactive, frigid Lamellic Eutrudepts
TYPICAL PEDON: Drexel loam - forest cover. (Colors are for dry soil unless otherwise stated.)
0i--0 to 1 inch; needles, leaves, twigs, and decomposing organic material.
A--1 to 3 inches; grayish brown (10YR 5/2) loam, very dark brown (10YR 2/2) moist; moderate medium and fine granular structure; slightly hard, very friable, slightly sticky; many fine roots; many fine interstitial pores; 10 percent hard shale fragments, slightly acid (pH 6.3); gradual smooth boundary. (0 to 4 inches thick)
E1--3 to 7 inches; light gray (10YR 7/2) channery silt loam, grayish brown (10YR 5/2) moist; moderate fine subangular blocky structure; slightly hard, very friable, slightly sticky, slightly plastic; many fine and medium roots; many fine tubular pores; 25 percent hard shale fragments; sand and silt mostly clear and unstained; slightly acid (pH 6.1); gradual wavy boundary. (2 to 8 inches thick)
E2--7 to 15 inches; very pale brown (10YR 7/3) very channery silt loam, pale brown (10YR 6/3) moist; moderate medium subangular blocky structure; slightly hard, very friable, slightly sticky, slightly plastic; common tubular pores; 40 percent hard shale fragments; silt grains are clean and unstained; slightly acid (pH 6.2); gradual wavy boundary. (5 to 10 inches thick)
E3--15 to 27 inches; very pale brown (10YR 8/2) very channery silt loam, pale brown (10YR 6/3) moist; weak fine subangular blocky structure; hard, very friable, slightly sticky, slightly plastic; common fine roots; many very fine and common fine and medium tubular pores; silt grains are clean and unstained; 50 percent hard shale fragments; slightly acid (pH 6.3); clear wavy boundary. (8 to 16 inches thick)
E and Bt1--27 to 43 inches; very pale brown (10YR 8/2) very channery silt loam, light yellowish brown (2.5Y 6/3) moist; discontinuous yellowish brown (10YR 5/4) silt loam lamellae, dark yellowish brown (10YR 4/4) moist, 1/8 to 1/4 inch thick, 1 to 2 inches apart; weak fine subangular blocky structure; hard, very friable, slightly sticky, slightly plastic; common fine roots; common fine tubular pores; 40 percent hard shale fragments; slightly acid (pH 6.2); gradual wavy boundary. (12 to 24 inches thick)
E and Bt2--43 to 60 inches; very pale brown (10YR 8/3) very channery loam, pale brown (10YR 6/3) moist; with light yellowish brown (10YR 6/4) loam lamellae, yellowish brown (10YR 5/4) moist, 1/4 to 1/2 inch thick and 2 inches apart, with continuous clayflow through lamellae; weak medium platy structure that separates to moderate fine subangular blocky structure; hard, very friable, slightly sticky, slightly plastic; common roots; 45 percent hard shale fragments; slightly acid (pH 6.3).
TYPE LOCATION: Mineral County, Montana; approximately 1,000 feet west of center of sec. 22, T.18N., R.29W.
RANGE IN CHARACTERISTICS: Depth to bedrock ranges from 40 to 80 inches. Drexel soils are loam or silt loam with from 5 to 10 percent clay, 65 to 75 percent silt plus very fine sand and angular shale fragments ranging from 10 to 20 percent in upper A horizons and from 35 to 75 percent below depths ranging from 6 to 20 inches, increasing in volume with increasing depth. Shale fragments have an estimated density of 2 and a hardness of 1 or 2. The annual soil temperature ranges from 44 degrees to 47 degrees F. and the average summer soil temperature ranges from 59 degrees to 64 degrees F. without an 0 horizon in cleared areas. The soils range from moderately acid to neutral and have base saturation of 65 to 80 percent in the upper foot of the profile and 85 to 95 percent in the lower horizons. The cation exchange capacity-clay ratio ranges from 1.2 to 1.9 below the 0 horizon. Hue ranges from 2.5Y through 7.5YR. The A1 horizon has value of 5 or 6. The A2 horizon has value of 7 or 8 and chroma of 2 or 3. The lamellae have value of 5 or 6 and chroma of 3 or 4.
COMPETING SERIES: These are the Lantern, Selway, and Winfall series. Lantern soils have 15 to 40 percent mica in the particle-size control section. Selway soils have more than 50 percent coarse or very coarse sand in the particle-size control section. Winfall soils have 10 to 20 percent clay in the particle-size control section
GEOGRAPHIC SETTING: Drexel soils are on steep mountain slopes ranging in elevation from 3,000 to 5,500 feet under open coniferous forest and grassland on shaly parent materials. Mean annual precipitation is estimated as 25 to 40 inches with moderately deep snow cover. Mean annual temperature is estimated as ranging from 40 degrees to 45 degrees F. and mean summer temperature is estimated as ranging from 55 degrees to 65 degrees F.
GEOGRAPHICALLY ASSOCIATED SOILS: Drexel soils are associated with Craddock, Coldcreek, Holloway, and Sharrott soils. Coldcreek soils have an argillic horizon.
DRAINAGE AND PERMEABILITY: Well-drained; medium runoff under forest cover; moderate permeability.
USE AND VEGETATION: Principal uses are forest products, watershed, and forage for domestic wildlife. Ponderosa pine and Douglas-fir dominate the overstory with serviceberry, spiraea, kinnikinnick, rose, and pinegrass in the understory.
DISTRIBUTION AND EXTENT: Western Montana in the Rocky Mountains. Drexel soils are moderately extensive.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana
SERIES ESTABLISHED: St. Regis-Ninemile Area, Mineral County, Montana, 1970.
REMARKS: Diagnostic horizons and features recognized in this pedon are an ochric epipedon from 1 to 7 inches (A, E1 horizons); an albic horizon from 3 to 27 inches (E1, E2, E3 horizons); a cambic horizon from 26 to 60 inches (E and Bt1, E and Bt2 horizons). Drexel soils have a frigid temperature regime and a udic moisture regime.