LOCATION SYBLON MTEstablished Series
TAXONOMIC CLASS: Fine, smectitic, frigid Aridic Argiustolls
TYPICAL PEDON: Syblon loam, grassland. (Colors are for dry soil unless otherwise noted.)
A11--0 to 10 cm; grayish brown (10YR 5/2) loam, very dark grayish brown (10YR 3/2) moist; moderate very fine granular structure; soft, very friable, slightly sticky and slightly plastic; many fine and very fine roots and few medium roots; few igneous pebbles; medium acid (pH 6.0); clear wavy boundary. (8 to 13 cm thick)
A12--10 to 23 cm; brown (10YR 5/3) loam, dark brown (10YR 3/3) moist; weak very fine and fine platy structure parting to moderate fine granular; slightly hard, friable, sticky and plastic; many fine and very fine roots and few medium roots; many fine and very fine pores; few igneous pebbles; medium acid (pH 6.0); clear wavy boundary. (10 to 18 cm thick)
B21t--23 to 38 cm; brown (10YR 5/3) clay, dark brown (10YR 4/3) moist; strong medium prismatic structure parting to strong fine and very fine subangular blocky; very hard, firm, sticky and very plastic; common fine and very fine roots and few medium roots; many fine and very fine pores; 10 percent soft shale fragments; thin clay films on faces of peds; light brownish gray (10YR 6/2) silt skeletans on tops of prisms and on vertical faces of peds; medium acid (pH 6.0); gradual wavy boundary.
B22t--38 to 53 cm; brown (10YR 5/3) clay, dark brown (10YR 4/3) moist; weak medium and coarse prismatic structure parting to moderate medium and fine angular blocky; very hard, firm, sticky and plastic; common fine and very fine roots and few medium roots; many fine and very fine pores; 10 percent soft shale fragments; thin continuous clay films on faces of peds; mildly alkaline (pH 7.4); gradual wavy boundary. (B2t horizons are 20 to 38 cm thick)
B3--53 to 74 cm; dark gray (10YR 4/1) clay, very dark gray (10YR 3/1) moist; weak very coarse prismatic structure parting to weak medium platy; extremely hard, very firm, very sticky and very plastic; common fine and very fine roots; many very fine pores and common fine pores; 30 percent soft shale fragments and 10 percent hard shale fragments; mildly alkaline (pH 7.6); diffuse boundary. (8 to 20 cm thick)
Cr--74 to 152 cm; grayish brown (2.5Y 5/2) clayey shale, dark grayish brown (2.5Y 4/2) moist; strong fine and very fine platy structure; extremely hard, extremely firm; few roots to 34 inches; common fine irregular filaments and soft masses of lime; masses of gypsum between 74 and 89 cm.
TYPE LOCATION: Fergus County, Montana; about 280 meters south and 30 meters east of the NW corner of sec. 7, T. 15 N., R. 24 E.
RANGE IN CHARACTERISTICS:
Soil temperature:5.0 to 8.0 degrees C.
Depth to bedrock:51 to 102 cm cm
A11 and A12 horizons:
Hue:10YR or 2.5Y
Value, dry:5
Value, moist:3
Chroma:2 or 3
Texture, F2 mm:loam
Clay content:18 to 27 percent
Rock fragments:0 to trace shale fragments
Reaction:pH 5.6 to 7.3
B21t and B22t horizons:
Hue:10YR or 2.5Y
Value, dry:5 or 6
Value, moist:4 or 5
Chroma:2 or 3
Texture, F2 mm:clay
Clay content:40 to 55 percent
Rock fragments:10 to 40 percent shale fragments
Soft shale:10 to 25 percent
Hard shale: 0 to 15 percent
Reaction:pH 5.6 to 7.8
B3 horizon:(The darker colors are inherited from the shale.)
Hue:10YR or 2.5Y
Value, dry:4 to 6
Value, moist:3 to 5
Chroma:1 to 4
Textures, F2 mm:clay or heavy clay loam
Clay content:35 to 55 percent
Rock fragments:30 to 70 percent shale fragments
Soft shale:30 to 55 percent
Hard shale: 0 to 15 percent
Reaction:pH 7.4 to 8.4
NOTE: In some pedons this horizon is calcareous.
Cr horizon:Hard fissile shale that is rippable. Gypsum and lime are between layers of shale in the upper 13 to 30 cm.
COMPETING SERIES: There are no competing series.
GEOGRAPHIC SETTING: Syblon soils are on uplands. Elevations are 670 to 1,160 meters. Slopes are 2 to 8 percent. Syblon soils formed in residuum of consoli- dated shale and in locally transported material overlying the consolidated shale. The climate is cool, with long cold winters, moist springs, and hot dry summers. Mean annual temperature is 4.0 to 7.0 degrees C. Mean annual precipi- tation is 255 to 355 mm, most of which falls during spring and early summer. The growing season is 115 to 135 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Creed, Dilts, Lisam, Tanna, and Weingart series. Creed soils are deeper than 102 cm to a paralithic contact and have an ochric epipedon. Dilts and Lisam soils are shallow over consoli- dated shale. Tanna soils lack the abrupt textural change. Weingart soils have A horizons less than 13 cm thick and have a natric horizon.
DRAINAGE AND PERMEABILITY: Well drained; slow to medium runoff; very slow permeability.
USE AND VEGETATION: Syblon soils are used for rangeland, pasture land, and cropland. The potential native vegetation is mainly western wheatgrass, needle- andthread, prairie junegrass, bluebunch wheatgrass, forbs, and shrubs.
DISTRIBUTION AND EXTENT: Central and eastern Montana. Syblon soils are moder- ately extensive.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Denver, Colorado
SERIES PROPOSED: Petroleum County, Montana, 1968.