LOCATION SIXTEENMILE             MT

Tentative Series
Ird. EMM/RJS
10/2013

SIXTEENMILE SERIES

The Sixteenmile series consists of very shallow, well drained soils that formed in colluvium or residuum from hard sedimentary bedrock. These soils are on escarpments and hills. Slopes are 2 to 70 percent. Mean annual precipitation is about 400 millimeters and mean annual air temperature is about 5 degrees C.

TAXONOMIC CLASS: Loamy-skeletal, mixed, superactive, nonacid, frigid Lithic Ustorthents

TYPICAL PEDON: Sixteenmile very channery loam, 15 percent slope in rangeland (colors are for dry soil unless otherwise noted).

A1--0 to 4 centimeters; reddish brown (5YR 5/3) very channery loam, dark reddish brown (5YR 3/3) moist; weak very fine granular structure; soft, very friable, slightly sticky and slightly plastic; many very fine and fine roots; 55 percent channers; neutral (pH 7.0); clear smooth boundary. (4 to 10 cm thick)

Bw--4 to 10 centimeters; light reddish brown (5YR 6/4) extremely channery loam, reddish brown (5YR 4/4) moist; moderate very fine granular structure; soft, very friable, slightly sticky and nonplastic; few very fine and medium roots; 75 percent channers; 2 percent flagstones; neutral (pH 7.2); abrupt smooth boundary. (5 to 15 cm thick)

R--10 centimeters; hard, strongly cemented shale bedrock.

TYPE LOCATION: Meagher County, Montana; Catlin Springs topographic quadrangle. UTM 12T, 0503158e, 5136625n. NAD27.

RANGE IN CHARACTERISTICS:

Soil temperature - 5 to 7 degrees C.
Mollic epipedon thickness - 4 to 10 centimeters.
Depth to bedrock - 10 to 25 centimeters.

A horizon
Hue - 5YR to 10YR
Value - 5 or 6 dry, 2 to 4 moist
Chroma - 2 or 3, dry or moist
Texture - loam or sandy loam
Clay content - 5 to 15 percent
Rock fragments - 35 to 70 percent--30 to 70 percent channers, 0 to 15 percent flagstones
Reaction - pH 6.6 to 7.8

Bw horizon
Hue - 5YR to 10YR
Value - 5 or 6 dry, 3 or 4 moist
Chroma - 3 or 4, dry or moist
Texture - loam or sandy loam
Clay content - 10 to 18 percent
Rock fragments - 40 to 80 percent--40 to 75 percent channers, 0 to 15 percent flagstones
Reaction - pH 6.6 to 7.8

Some pedons may have a thin Cr horizon above the R horizon.

COMPETING SERIES:
Ashbon(MT) - is 25 to 50 centimeters to a lithic contact.
Ashbray(MT) - is 25 to 50 centimeters to a lithic contact.

GEOGRAPHIC SETTING:
Landform - bedrock-floored plains, escarpments and hills.
Elevation - 1500 to 1900 meters.
Slope - 2 to 70 percent.
Parent material - colluvium or residuum derived from hard sedimentary bedrock, including the Spokane Shale formation.
Climate - long, cold winters; moist springs; short, warm summers.
Mean annual precipitation - 380 to 480 millimeters, most of which falls during spring and early summer.
Mean annual air temperature - 4 to 7 degrees C.
Frost-free period - 70 to 100 days.

GEOGRAPHICALLY ASSOCIATED SOILS: None listed.

DRAINAGE AND PERMEABILITY: Well drained; moderate permeability.

USE AND VEGETATION: Sixteenmile soils are used mainly for rangeland. The potential native vegetation is mainly bluebunch wheatgrass, Idaho fescue, needleandthread, western wheatgrass, forbs, and shrubs.

DISTRIBUTION AND EXTENT: Sixteenmile soils are of small extent in west-central Montana. MLRAs 43B, 44B and 46.

MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana

SERIES PROPOSED: Meagher County, Montana, 2012. The Sixteenmile soil is named for a nearby road.

REMARKS:
Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - from the surface to 4 centimeters (A horizon)
Particle-size control section - from the surface to 8 centimeters (A and Bw horizons)
Lithic contact - at a depth of 10 centimeters (R horizon)

Sixteenmile soils have a frigid temperature regime and an ustic moisture regime.

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National Cooperative Soil Survey
U.S.A.