LOCATION PLACERTON MT
Established Series
Rev. PEM-JAL-EMM
04/2014
PLACERTON SERIES
The Placerton series consists of moderately deep, well drained soils that formed in colluvium, slope alluvium or residuum derived from granite bedrock. These soils are on ridges, divides and sideslopes of hills and mountains. Slopes are 2 to 35 percent. Mean annual precipitation is about 17 inches and mean annual air temperature is about 40 degrees F.
TAXONOMIC CLASS: Fine-loamy, mixed, superactive, frigid Typic Argiustolls
TYPICAL PEDON: Placerton gravelly sandy clay loam, in rangeland (colors are for dry soil unless otherwise noted).
A--0 to 7 inches; grayish brown (10YR 5/2) gravelly sandy clay loam, very dark grayish brown (10YR 3/2) moist; weak medium and fine subangular blocky structure; soft, very friable, moderately sticky and slightly plastic; many very fine and few fine roots; many very fine and fine and few medium pores; 20 percent gravel; neutral (pH 6.6); clear smooth boundary. (4 to 8 inches thick)
Bt1--7 to 11 inches; brown (10YR 5/3) gravelly clay loam, dark brown (10YR 3/3) moist; moderate medium prismatic structure parting to moderate medium and fine subangular blocky; slightly hard, friable, moderately sticky and slightly plastic; many very fine and few fine roots; many very fine and few fine tubular and interstitial pores; many faint clay films on faces of peds; 30 percent gravel; neutral (pH 6.8); clear smooth boundary.
Bt2--11 to 21 inches; brown (10YR 5/3) gravelly sandy clay loam, brown (10YR 4/3) moist; moderate medium prismatic structure parting to moderate medium and fine subangular blocky; slightly hard, friable, moderately sticky and slightly plastic; common very fine and few fine roots; many very fine and few fine tubular and interstitial pores; many faint clay films bridging sand grains and on faces of peds; 25 percent gravel; neutral (pH 7.0); clear smooth boundary. (Combined thickness of Bt horizons is 6 to 16 inches).
Bk--21 to 29 inches; very pale brown (10YR 7/3) gravelly sandy loam, light yellowish brown (10YR 6/4) moist; moderate medium and fine subangular blocky structure; slightly hard, very friable, slightly sticky and nonplastic; few very fine roots; common very fine tubular and interstitial pores; 30 percent gravel; disseminated lime; few fine masses of lime; strongly effervescent; moderately alkaline (pH 8.3); clear smooth boundary. (8 to 18 inches thick)
Cr--29 to 58 inches; grayish brown (2.5Y 5/2) decomposed granite bedrock (grus) that crushes to very gravelly coarse sand or loamy coarse sand; slightly alkaline (pH 7.8). (25 to 32 inches thick)
R--58 inches; hard granite bedrock.
TYPE LOCATION: Jefferson County, Montana; 1,000 feet south and 900 feet west of the NE corner of sec. 5, T. 5 N., R. 4 W.
RANGE IN CHARACTERISTICS:
Soil temperature - 38 to 44 degrees F.
Moisture control section - between 4 and 12 inches.
Mollic epipedon thickness - 7 to 15 inches.
Depth to argillic horizon - 6 to 16 inches.
Depth to Bk horizon - 15 to 30 inches.
Depth to Cr horizon - 20 to 40 inches.
Depth to bedrock - 40 to 60 inches.
A thin Btk horizon is present in some pedons.
A horizon
Hue: 10YR or 2.5Y
Value: 4 or 5 dry; 2 or 3 moist
Chroma: 2 or 3, dry or moist
Texture: sandy loam or sandy clay loam
Clay content: 10 to 25 percent
Rock fragments: 5 to 25 percent gravel (mainly less than 7mm in diameter), 0 to 5 percent cobbles and stones
Reaction: pH 6.1 to 7.3
Bt horizons
Hue: 10YR or 2.5Y
Value: 5 or 6 dry; 3, 4, or 5 moist
Chroma: 3 or 4, dry or moist
Texture: loam, sandy clay loam, or clay loam
Clay content: 20 to 30
Rock fragments: 5 to 30 percent gravel (mainly less than 7mm in diameter), 0 to 5 percent cobbles
Reaction: pH 6.6 to 7.8
Bk horizon
Hue: 10YR or 2.5Y
Value: 6 or 7 dry; 5 or 6 moist
Chroma: 2, 3, or 4 dry or moist
Texture: coarse sandy loam, sandy loam, loam, or sandy clay loam
Clay content: 10 to 25 percent
Rock fragments: 10 to 35 percent gravel (mainly less than 7mm in diameter)
Calcium carbonate equivalent: 5 to 15 percent
Reaction: pH 7.9 to 8.4
COMPETING SERIES:
Absarook (MT) - does not have a paralithic contact above the lithic contact.
Beartooth (MT) - does not have a lithic contact above a depth of 60 inches.
Beeno (WY) - does not have a lithic contact above a depth of 60 inches.
Bielenberg (MT) - does not have lime above a depth of 40 inches; does not have a lithic contact above a depth of 60 inches.
Bookcliff (UT) - does not have a lithic contact above a depth of 60 inches.
Bullflat (SD) - does not have a lithic contact above a depth of 60 inches.
Burtoner (MT) - does not have horizon of secondary carbonate accumulation; has a lithic contact at 23 to 40 inches.
Clancy (MT) - does not have a horizon of secondary carbonates above the paralithic contact.
Clasoil (MT) - does not have a lithic contact above a depth of 60 inches.
Cortyzack (CO) - does not have a lithic contact above a depth of 60 inches.
Dooley (MT) - has substratum of till that has a bulk density of 1.55 and greater; does not have a lithic contact above a depth of 60 inches.
Empedrado (CO) - does not have a lithic contact above a depth of 60 inches.
Fairfield (MT) - does not have a lithic contact above a depth of 60 inches.
Farnuf (MT) - does not have a lithic contact above a depth of 60 inches.
Felor (SD) - does not have a lithic contact above a depth of 60 inches.
Greenway (SD) - does not have a lithic contact above a depth of 60 inches.
Gurney (SD) - has a lithic contact at depths of 20 to 40 inches.
Hangdo (UT) - does not have lime above a depth of 40 inches; does not have a lithic contact above a depth of 60 inches.
Hoppers (MT) - has a lithic contact at 20 to 40 inches; does not have horizon of secondary carbonate accumulation.
Hyalite (MT) - has a discontinuity of sandy-skeletal material above 40 inches and immediately below the argillic horizon; does not have a lithic contact above a depth of 60 inches.
Jeffcity (MT) - has the lithic bedrock at a depth of 20 to 40 inches.
Lefor (ND) - does not have a lithic contact above a depth of 60 inches.
Lininger (CO) - does not have a lithic contact above a depth of 60 inches.
Livona (ND) - does not have a lithic contact above a depth of 60 inches.
Martinsdale (MT) - does not have a lithic contact above a depth of 60 inches.
Maudlin (CO) - does not have a Bk horizon; has a lithic contact at depths of 20 to 40 inches.
Meagher (MT) - does not have a lithic contact above a depth of 60 inches.
Moen (CO) - has a lithic contact at depths of 20 to 40 inches; does not have a paralithic contact above the lithic contact.
Pianohill (MT) - has a lithic contact at depths of 20 to 40 inches; does not have horizon of secondary carbonate accumulation.
Reeder (ND) - does not have a lithic contact above a depth of 60 inches.
Reedwest (MT) - does not have a lithic contact above 60 inches.
Snakejohn (UT) - does not have a paralithic contact above the lithic contact; has a calcic horizon.
Sponseller (AZ) - does not have a paralithic contact above the lithic horizon; does not have a lithic contact above a depth of 60 inches.
Trag (CO) - does not have a paralithic contact above the lithic contact; does not have a lithic contact above a depth of 60 inches.
Trazuni (NM) - does not have a lithic contact above 60 inches.
Tschicoma (NM) - does not have a paralithic contact above a lithic contact; does not have a lithic contact above a depth of 60 inches.
Ulrant (WY) - does not have a paralithic contact at 20 to 40 inches and above a lithic contact; has a BA horizon.
Vida (MT) - has substratum of till that has a bulk density of 1.55 and greater; does not have a lithic contact above a depth of 60 inches.
Watrous (ND) - has a lithic contact at depths of 20 to 40 inches.
Wemple (MT) - does not have a paralithic contact over a lithic contact; does not have lithic contact above a depth of 60 inches.
Williams (ND) - does not have a lithic contact above a depth of 60 inches.
Yegen (MT) - does not have a lithic contact above a depth of 60 inches.
GEOGRAPHIC SETTING:
Landform - ridges, divides and sideslopes of hills and mountains.
Elevation - 4,800 to 6,000 feet.
Slope - 2 to 35 percent.
Parent material - colluvium, slope alluvium or residuum derived from granite bedrock.
Climate - long, cold winters; moist springs; warm summers.
Mean annual precipitation - 15 to 19 inches.
Mean annual air temperature - 36 to 42 degrees F.
Frost-free period - 70 to 105 days.
GEOGRAPHICALLY ASSOCIATED SOILS: None listed.
DRAINAGE AND PERMEABILITY: Well drained; moderate permeability in the argillic horizon and moderately rapid below.
USE AND VEGETATION: Placerton soils are primarily used for rangeland and hayland. The potential native vegetation is mainly rough fescue, Idaho fescue, bluebunch wheatgrass, prairie junegrass, lupine, fringed sagewort, milkvetch, and big sagebrush. Some areas have widely scattered ponderosa pine, Douglas fir, and common juniper.
DISTRIBUTION AND EXTENT: Placerton soils are of small extent in southwestern Montana. MLRA 43B.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana
SERIES ESTABLISHED: Jefferson County, Montana, 1998.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon - from the soil surface to 11 inches (A, Bt1 horizons)
Argillic horizon - from 7 to 21 inches (Bt1, Bt2 horizons)
Particle-size control section - from 7 to 21 inches (Bt1, Bt2 horizons)
A horizon of secondary calcium carbonate - from 21 to 29 inches (Bk horizon)
Paralithic contact - a layer of decomposed granite bedrock (grus) from 29 to 58 inches (Cr horizon)
Lithic contact - hard granite bedrock at 58 inches (R horizon).
Soil interpretation record: MT1576, MT1577.
Placerton soils have a frigid temperature regime and an ustic moisture regime.
National Cooperative Soil Survey
U.S.A.