LOCATION CABSTON MTEstablished Series
TAXONOMIC CLASS: Clayey-skeletal, smectitic, frigid Aridic Haplustolls
TYPICAL PEDON: Cabston channery clay loam, native grassland. (Colors are for dry soil unless otherwise noted.)
A1--0 to 10 cm; grayish brown (10YR 5/2) channery clay loam, very dark grayish brown (10YR 3/2) moist; moderate fine and very fine granular structure; slightly hard, friable, sticky and plastic; many fine and very fine roots and common medium roots; 25 percent hard flat shale and flat angular sandstone pebbles; neutral (pH 7.2); clear wavy boundary. (8 to 20 cm thick)
B2--10 to 36 cm; grayish brown (10YR 5/2) very channery heavy clay loam, very dark grayish brown (10YR 3/2) moist; weak medium and coarse prismatic structure parting to moderate fine and medium subangular blocky; slightly hard, friable, sticky and plastic; many fine and very fine roots and common medium roots; many fine and very fine pores and few medium pores; 35 percent hard flat shale and flat angular sandstone pebbles; mildly alkaline (pH 7.4); clear irregular boundary. (10 to 56 cm thick)
B3--36 to 53 cm; light brownish gray (10YR 6/2) very channery heavy clay loam, dark grayish brown (10YR 4/2) moist; weak very coarse prismatic structure parting to weak fine and medium subangular blocky; slightly hard, friable, sticky and plastic; many fine and very fine roots and common medium roots; many fine and very fine pores and few medium pores; 40 percent hard flat shale and flat angular sandstone pebbles; strongly effervescent; mildly alkaline (pH7.6); gradual wavy boundary. (8 to 25 cm thick)
C1--53 to 79 cm; light brownish gray (2.5Y 6/2) very channery clay loam, dark grayish brown (2.5Y 4/2) moist; moderate fine granular structure; slightly hard, friable, sticky and plastic; common fine and very fine roots and few medium roots; many fine and very fine pores and few medium pores; 60 percent hard flat shale and flat angular sandstone pebbles; strongly effervescent; patchy lime coating on coarse fragments; mildly alkaline (pH 7.6); diffuse boundary. (20 to 35 cm thick)
C2--79 to 168 cm; light brownish gray (2.5Y 6/2) very channery heavy clay loam, dark grayish brown (2.5Y 4/2) moist; weak fine granular structure; slightly hard, friable, sticky and plastic; few fine and very fine roots; few fine and very fine pores; 60 percent hard flat shale and flat angular sandstone pebbles; strongly effervescent; mildly alkaline (pH 7.6).
TYPE LOCATION: Fergus County, Montana; 170 meters south and 700 meters west of the NE corner of sec. 25, T. 15 N., R. 23 E.
RANGE IN CHARACTERISTICS:
Soil temperature: 5.5 to 8.5 degrees C.
Mollic epipedon thickness: 18 to 38 cm
Rock fragments: consolidated shale and sandstone
Depth to lime: 31 to 76 cm
A1 horizon:
Hue: 10YR or 2.5Y
Value, dry: 5
Value, moist: 3
Chroma: 2
Texture, F2 mm: clay loam
Clay content: 27 to 40 percent
Rock fragments: 10 to 60 percent
Flagstones: 0 to 5 percent
Pebbles, flat angular: 10 to 55 percent
Reaction: pH 6.6 to 7.8
B2 horizon:
Hue: 10YR or 2.5Y
Value, dry: 5 or 6
Value, moist: 3 or 4
Chroma: 2 or 3
Texture, F2 mm: clay loam
Clay content: 35 to 40 percent
Rock fragments: 15 to 60 percent
Flagstones: 0 to 5 percent
Pebbles, flat angular: 15 to 55 percent
Reaction: pH 6.6 to 7.8
B3 horizon:
Hue: 10YR or 2.5Y
Value, dry: 5 or 6
Value, moist: 4
Chroma: 2
Texture, F2 mm: clay loam
Clay content: 35 to 40 percent
Rock fragments: 10 to 60 percent
Flagstones: 0 to 5 percent
Pebbles, flat angular: 10 to 55 percent
Reaction: pH 7.4 to 8.4
C horizon:
Hue: 10YR or 2.5Y
Value, dry: 4 to 6
Value, moist: 4 or 5
Chroma: 2
Texture, F2 mm: heavy clay loam, or light clay
Clay content: 35 to 50 percent
Rock fragments: 35 to 60 percent
Flagstones: 0 to 5 percent
Pebbles, flat angular: 35 to 55 percent
Reaction: pH 7.4 to 8.4
COMPETING SERIES: There are no competing series. Close competitors are the Arle and Redthayne series. Both are loamy-skeletal. In addition, the Arle soils have a paralithic contact above a depth of 102 cm and the Redthayne soils have a ca horizon.
GEOGRAPHIC SETTING: Cabston soils are on foot slopes and fans and have slope gradients of 2 to 60 percent. Elevations are 920 to 1,160 meters. The Cabston soils formed in alluvium and colluvium derived from shales and sandstone. The climate is cool with long cold winters and moist springs and dry summers. Mean annual precipitation is 255 to 355 mm, most of which falls during spring and early summer. Mean annual temperature is 5.5 to 7.0 degrees C. The growing season is 115 to 135 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are Delpine, Tanna, and Ethridge series. Delpine soils are shallow to shale or to sandstone. Tanna and Ethridge soils have argillic horizons and lack the high percentage of rock fragments in the control section.
DRAINAGE AND PERMEABILITY: Well drained; medium and rapid runoff; moderately slow permeability.
USE AND VEGETATION: Cabston soils are used mainly for rangeland and to a lesser degree for cropland or pasture. The potential native vegetation is mainly bluebunch wheatgrass, western wheatgrass, green needlegrass, forbs, and shrubs.
DISTRIBUTION AND EXTENT: Central Montana. Cabston soils are moderately extensive.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Denver, Colorado
SERIES ESTABLISHED: Fergus County, Montana, 1979.