LOCATION MAGINNIS MTEstablished Series
TAXONOMIC CLASS: Clayey-skeletal, smectitic, frigid Lithic Haplustolls
TYPICAL PEDON: Maginnis channery clay loam - native grass. (Colors are for dry soil unless otherwise noted)
A11--0 to 4 inches; grayish brown (2.5Y 5/2) channery clay loam, very dark grayish brown (2.5Y 3/2) moist; fine granular structure; slightly hard, friable, sticky, plastic; many very fine roots; neutral (pH 7.2); gradual boundary. (2 to 8 inches thick)
A12--4 to 16 inches; grayish brown (2.5Y 5/2) very channery clay loam, very dark grayish brown (2.5Y 3/2) moist; many soft plates of black shale and hard cherty sandstone that increase in the lower part; moderate fine and very fine blocky structure; hard, friable, very sticky, very plastic; distinct continuous films on all peds and on chert fragments; many very fine roots; mildly alkaline (pH 7.4); abrupt boundary. (10 to 16 inches thick)
R1--16 to 22 inches; fractured gray cherty sandstone with clay and clayey shale between the layers and clay in the fractures; few roots; noncalcareous. (0 to 10 inches thick)
R2--22 inches; hard phyllitic shale and platy sandstone, noncalcareous.
TYPE LOCATION: Judith Basin County, Montana; on east side of trail, 1,200 feet north, 1,020 feet east of SW corner sec. 16, T.15N., R.13E.
RANGE IN CHARACTERISTICS: Maginnis soils have mean annual soil temperature ranging from 41 degrees to 47 degrees F. and average summer temperature ranging from 60 degrees to 64 degrees F. Depth to the R1 layer ranges from 8 to 20 inches. The A1 horizon has hue of 10YR or 2.5Y, and value of 5 through 3 dry. It is cobbly or channery clay loam or clay with 35 to 50 percent clay. Shale or sandstone fragments make up 50 to 90 percent of the volume below a depth of about 4 inches. Thin coatings of lime occur in some crevices and under some plates in the bedrock substrata.
COMPETING SERIES: These are the Amherst, Castner, Cheadle, and Ringling series. Amherst soils have an argillic horizon. Castner soils have loamy-skeletal particle-size class. Cheadle soils have loamy-skeletal particle-size class and have summer temperatures colder than 59 degrees F. Ringling soils have fragmental particle-size class.
GEOGRAPHIC SETTING: Maginnis soils are on upland bedrock plains. The soils formed in clay loam and clay materials from sedimentary rock origin. The climate is cool, moist, semiarid with a mean annual temperature of 40 degrees to 45 degrees F. and mean annual precipitation ranging from 14 to 18 inches. Mean summer temperature ranges from 60 degrees to 65 degrees F. Mean winter temperature ranges from 20 degrees to 25 degrees F.
PRINCIPAL ASSOCIATED SOILS: These are the competing Amherst and Cheadle soils and the Absarokee and Alder soils. Absarokee and Alder soils lack bedrock strata within a 20 inch depth.
DRAINAGE AND PERMEABILITY: Excessively drained; rapid runoff.
USE AND VEGETATION: Mainly used for native grass range, but some is used for dryland grain production. Principal native vegetation is blue grama, fringed sagewort, prairie junegrass, western wheatgrass, phlox, lichens, and curlycup gumweed.
DISTRIBUTION AND EXTENT: Central Montana, bordering the eastern front of the Northern Rocky Mountains. The series is of moderate extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Denver, Colorado
SERIES ESTABLISHED: Reconnaissance Soil Survey of Central Montana, 1946.
REMARKS: The Maginnis soils were formerly classified as Chestnut soils intergrading to Lithosols.
OSED scanned by SSQA. Last revised by state on 4/73.