LOCATION MOCMONT MT+SD
Established Series
Rev. GLS/JAL/KLS
03/2022
MOCMONT SERIES
The Mocmont series consists of very deep, well drained soils that formed in colluvium or alluvium weathered from argillite, igneous rock, or sandstone. These soils are on alluvial fans, hills, and mountains. Slopes are 2 to 60 percent. Mean annual precipitation is about 510 mm, and mean annual air temperature is about 6 degrees C.
TAXONOMIC CLASS: Loamy-skeletal, mixed, superactive, frigid Typic Haplustalfs
TYPICAL PEDON: Mocmont very gravelly loam, forested (colors are for dry soil unless otherwise noted).
Oi--0 to 6 cm; forest litter of undecomposed and partially decomposed needles, twigs, cones, and leaves.
E--6 to 29 cm; very pale brown (10YR 7/3) very gravelly loam, brown (10YR 4/3) moist; moderate fine and very fine granular structure; soft, very friable, slightly sticky and nonplastic; many medium, fine, very fine, and few coarse roots; many very fine pores; 30 percent angular pebbles, 10 percent angular cobbles; slightly acid (pH 6.2); clear wavy boundary. (13 to 41 cm thick)
E/Bt--29 to 36 cm; E part (75 percent) very pale brown (10YR 7/3) very gravelly loam, brown (10YR 5/3) moist tongues; B part (25 percent) light brownish gray (10YR 6/2) very gravelly heavy loam, dark yellowish brown (10YR 4/4) moist; weak very fine subangular blocky structure parting to moderate very fine granular; hard, friable, slightly sticky and slightly plastic; many medium, fine, very fine, and common coarse roots; many fine and very fine pores; 35 percent angular pebbles, 15 percent angular cobbles; moderately acid (pH 5.6); gradual wavy boundary. (13 to 23 cm thick)
Bt1--36 to 67 cm; light yellowish brown (10YR 6/4) extremely gravelly clay loam, dark yellowish brown (10YR 4/4) moist; moderate fine and very fine subangular blocky structure; hard, friable, sticky and plastic; many fine and very fine, common medium and coarse roots; many fine and very fine pores; continuous distinct clay film on faces of peds; common faint clay film on rock fragments; 50 percent angular pebbles, 20 percent angular cobbles; moderately acid (pH 5.6); gradual wavy boundary.
Bt2--67 to 103 cm; pale brown (10YR 6/3) extremely gravelly clay loam, dark yellowish brown (10YR 4/4) moist; moderate fine and very fine subangular blocky structure; hard, friable, sticky and plastic; many very fine, common fine and medium roots, and few coarse roots; many fine and very fine pores; many faint thin clay films on faces of peds; common faint clay film on rock fragments; 55 percent angular pebbles, 25 percent angular cobbles; moderately acid (pH 5.6); diffuse wavy boundary. (Combined thickness of Bt horizons--20 to 114 cm.)
BC--103 to 158 cm; pale brown (10YR 6/3) extremely cobbly loam, dark yellowish brown (10YR 4/4) moist; weak very fine subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; common fine, very fine, and few medium roots; many very fine pores; 45 percent angular cobbles, 40 percent angular pebbles; moderately acid (pH 5.8).
TYPE LOCATION: Fergus County, Montana; about 360 meters west and 410 meters north of the SE corner of sec. 2, T. 16 N., R. 17 E.
RANGE IN CHARACTERISTICS:
Mean annual soil temperature--3 to 7 degrees C
Moisture control section--10 to 30cm
A thin dark-colored A horizon 3 to 10 cm thick is allowed.
Some pedons have a Bt/E horizon in place of the E/Bt horizon
E horizon
Hue--7.5YR or 10YR
Value--5 through 8 dry; 4 through 6 moist
Chroma--2 or 3
Texture--loam or sandy loam
Clay content--10 to 20 percent
Rock fragments--10 to 60 percent; 0 to 30 percent angular cobbles, 10 to 50 percent angular pebbles or channers
Reaction--pH 5.1 to 7.3
E/Bt or Bt/E horizon
Hue--7.5YR, 10YR or 2.5Y
Value--E part: 6 or 7, Bt part: 5 through 7 dry; E part: 4 or 5, Bt part: 4 or 5 moist
Chroma--1 through 4
Texture--E part: sandy loam or loam; Bt part: loam or clay loam
Clay content--E part: 10 to 20 percent, Bt part: 25 to 35 percent
Rock fragments--35 to 60 percent; 10 to 30 percent angular cobbles, 25 to 55 percent angular pebbles or channers
Reaction--pH 5.1 to 7.3
Bt horizon
Hue--5YR, 7.5YR, 10YR or 2.5Y
Value--5 through 7 dry; 4 or 5 moist
Chroma--3, 4, or 6
Texture--loam, clay loam, or sandy clay loam
Clay content--18 to 35 percent
Rock fragments--35 to 85 percent; 10 to 30 percent angular cobbles, 25 to 55 percent angular pebbles or channers
Reaction--pH 5.1 to 7.3
BC horizon
Hue--5YR, 7.5YR, 10YR or 2.5Y
Value--5 through 7 dry; 4 or 5 moist
Chroma--3, 4, or 6
Texture--loam, sandy loam or sandy clay loam
Clay content--10 to 25 percent
Rock fragments--60 to 90 percent; 15 to 40 percent cobbles and stones, 35 to 50 percent angular pebbles or channers
Reaction--pH 5.1 to 7.8
COMPETING SERIES:
Macmeal (MT) - has horizon of secondary carbonate accumulation.
Yourame (MT) - has horizon of secondary carbonate accumulation.
Yreka (MT) - does not have a glossic horizon.
GEOGRAPHIC SETTING:
Landform--hills, mountains, alluvial fans
Elevation--975 to 1,980 meters
Slope--2 to 60 percent
Parent material--colluvium or alluvium weathered from argillite, igneous, or sandstone rock
Climate--long, cold winters, moist springs, warm summers
Mean annual precipitation--380 to 660 mm
Mean annual air temperature--2 to 6 degrees C
Frost-free period--70 to 110 days
GEOGRAPHICALLY ASSOCIATED SOILS: None listed
DRAINAGE AND PERMEABILITY: Well drained; moderate permeability
USE AND VEGETATION: Mocmont soils are used mainly for forest products and range. Potential native vegetation is mainly Douglas fir and ponderosa pine with an understory of arrowleaf balsamroot, Oregon-grape, common juniper, common snowberry, russet buffaloberry, white spiraea, kinnikinnick, Idaho fescue, rough fescue, bluebunch wheatgrass, and pinegrass.
DISTRIBUTION AND EXTENT: Mocmont soils are of large extent in the mountains and foothills of central Montana and the Black Hills area of South Dakota; MLRAs 43B, 46, and 62
SOIL SURVEY REGIONAL OFFICE (SSRO) RESPONSIBLE: Bozeman, Montana
SERIES ESTABLISHED: Fergus County, Montana, 1979
REMARKS: Soil interpretation records: MT0387, MT8098, MT8185, MT0897, MT1069.
Diagnostic horizons and features recognized in this pedon are:
Albic horizon--6 to 29 cm (E horizon)
Glossic horizon--29 to 36 cm (E/Bt horizon)
Argillic horizon--36 to 103 cm (Bt1, Bt2 horizons)
Particle-size control section--36 to 86 cm (Bt1, part of Bt2 horizons)
Mocmont soils have a frigid temperature regime and an ustic moisture regime.
Series reclassified from Glossic Eutroboralfs in 1997.
Converted to metric and O horizons were updated to start at zero. 2/2022
National Cooperative Soil Survey
U.S.A.