LOCATION BYNUM MT+WYEstablished Series
TAXONOMIC CLASS: Fine-loamy, mixed, superactive Ustic Haplocryolls
TYPICAL PEDON: Bynum silt loam, cultivated. (Colors are for dry soil unless otherwise stated.)
A--0 to 6 inches; dark gray (10YR 4/1) silt loam, black (10YR 2/1) moist; moderate very thin platy structure that separates to moderate very fine granules; slightly hard, very friable, slightly sticky and slightly plastic; slightly alkaline (pH 7.8); clear irregular boundary with tongues 2 inches wide extending downward to 12 inches. (3 to 12 inches thick)
Bw1--6 to 9 inches; grayish brown (10YR 5/2) silty clay loam, dark brown (10YR 3/3) moist; weak coarse prisms that separate to moderate fine and very fine blocky structure; hard, firm, moderately sticky and moderately plastic; moderately alkaline (pH 8.0); clear irregular boundary.
Bw2--9 to 14 inches; grayish brown (2.5Y 5/2) silty clay loam, dark grayish brown (2.5Y 4/2) moist; weak coarse prisms that separate to moderate medium blocky structure; hard, firm, moderately sticky and moderately plastic; slightly effervescent; gradual wavy boundary. (Combined B horizon thickness ranges from 5 to 15 inches).
Bk--14 to 27 inches; light gray (5Y 7/2) silty clay loam, olive gray (5Y 5/2) moist; many very dark grayish brown (10YR 3/2) root stains; weak coarse prismatic structure that separates to weak coarse blocks and moderate fine granules; hard, friable, moderately sticky and moderately plastic; strongly effervescent with few threads of segregated lime in the upper part and many pale yellow (5Y 8/2) lime mottles in the lower part; strongly alkaline (pH 8.6); gradual wavy boundary.
BCk--27 to 38 inches; white (5Y 8/1) silty clay loam, light gray (5Y 7/2) moist; many grayish brown (2.5Y 5/2) and dark grayish brown (2.5Y 4/2) stainings from roots; medium platy structure; slightly hard, firm, moderately sticky and moderately plastic; strongly effervescent with common threads and film of segregated lime; gradual boundary. (5 to 15 inches thick)
Cr--38 to 60 inches; white to gray siltstone; strongly effervescent; strongly alkaline (pH 8.6).
TYPE LOCATION: Glacier County, Montana; 300 feet southeast of farmstead; 1,740 feet north, 20 feet east of center of section 10, T.37N., R.10W.
RANGE IN CHARACTERISTICS: Solum Thickness and depth to the Cca horizon range from 11 to 22 inches. Depth to shale ranges from 21 to 40 inches. Scattered sandstone slabs are throughout some pedons and a lag of quartzite and argillite gravel occurs on the surface in some pedons. Mean soil temperature ranges from 52 degrees to 59 degrees F. in the summer, 20 percent to 22 percent F. in the winter, and 29 degrees to 40 degrees F. annual temperature. The control section ranges from silty clay loam to loam and has 20 to 32 percent clay and 20 to 35 percent fine and coarser sand. Some pedons near the trees have thin 0 horizons or have a litter of needles.
The A horizon has value of 3 through 5 dry, 1 to 3 moist, and chroma of 1 or 2. It has strong granular or crumb structure.
The Bw horizon has hue of 10YR to 5Y and value of 4 or 5 dry, 3 to 5 moist. It has up to 5 percent more clay than the A horizon. This horizon has blocky or prismatic structure or has prismatic structure that separates to blocky.
The Bk and BCk horizons have hues of 2.5Y or 5Y, value of 6 through 8 dry, 5 to 6 moist, and chroma of 1 to 3. It is silty clay loam or clay loam and has fragments of bedrock throughout most parts. They contain moderate amounts of segregated lime as threads and nodules. Calcium carbonate equivalent is 5 to 15 percent.
COMPETING SERIES: These are the Auzqui, Emerald, Redcloud, Tamp, Tampico, Teton, Tilton, and Wrenman series. Auzqui, Emerald, Redcloud, Tamp, Tampico, and Tilton soils lack a paralithic contact within a depth of 40 inches. Teton and Wrenman soils have a lithic contact at depths ranging from 20 to 40 inches.
GEOGRAPHIC SETTING: Bynum soils are on terraces, fans and lower mountain slopes underlain by shale or soft loamstone. Slopes are 2 to 60 percent. Elevation is 4,400 to 6,000 feet, and up to 8,000 feet in Wyoming. Strata of sandstone are exposed within the landscape. They formed in thin alluvial or outwash deposits over soft sedimentary beds. The climate is cold and semiarid. Mean summer temperature is 57 degrees to 59 degrees F., mean winter temperature is 21 degrees to 22 degrees F., and mean annual temperature is 29 degrees to 40 degrees F. Precipitation ranges from 15 to 22 inches annually, most of which falls during spring and early summer. The (32 degrees F.) growing season is 50 to 70 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Adel, Doby, Fifer and Leavitt soils and the competing Michelson soils. Adel soils occur within Bynum soils landscape on accumulation positions. They lack an argillic horizon and have a thick mollic epipedon. Doby and Fifer soils lack argillic horizons and are shallow over shale. Doby soils formed in clayey shales. Leavitt soils are deep, have argillic horizons and they occur on the benchlands above Bynum soils or intermingled on the slopes wherever the mantle of old outwash material is still present.
DRAINAGE AND PERMEABILITY: Well drained; medium runoff; moderate permeability.
USE AND VEGETATION: Used primarily for native range with small acreage used for small grain production. Native species common to this soil are Idaho fescue, rough fescue, bearded wheatgrass, big bluegrass, bluebunch wheatgrass, and lupine, and low density stands of fir trees.
DISTRIBUTION AND EXTENT: Bynum series is inextensive, occurring in the major drainageway valleys at high elevations east of the Rocky Mountains.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana
SERIES ESTABLISHED: Glacier County (Blackfeet Reservation-Cut Bank Area), Montana, 1969.