LOCATION SURDAL                  MT

Established Series
Rev. DES-JMS-RJS
03/2012

SURDAL SERIES

The Surdal series consists of moderately deep, well drained soils that formed in slope alluvium and colluvium over residuum derived from hard fine grained igneous or metamorphic rock. These soils are on escarpments, ridges and mountain slopes. Slopes are 2 to 60 percent. Mean annual precipitation is about 18 inches, and mean annual air temperature is about 38 degrees F.

TAXONOMIC CLASS: Loamy-skeletal, mixed, superactive Ustic Haplocryolls

TYPICAL PEDON: Surdal cobbly loam, in rangeland (colors are for dry soil unless otherwise noted).

A1--0 to 7 inches; dark grayish brown (10YR 4/2) cobbly loam, very dark brown (10YR 2/2) moist; moderate fine and medium granular structure; slightly hard, very friable, slightly sticky and nonplastic; many very fine and fine roots; many very fine and fine interstitial pores; 10 percent cobbles, 10 percent gravel; slightly acid (pH 6.2); clear wavy boundary.

A2--7 to 13 inches; dark grayish brown (10YR 4/2) very cobbly loam, very dark grayish brown (10YR 3/2) moist; weak medium prismatic structure parting to moderate medium subangular blocky; slightly hard, very friable, slightly sticky and nonplastic; many very fine and fine roots; many very fine and fine interstitial pores; 15 percent cobbles, 25 percent gravel; slightly acid (pH 6.2); clear wavy boundary. (Combined thickness of A horizons is 7 to 14 inches).

Bw1--13 to 23 inches; grayish brown (10YR 5/2) very cobbly loam, brown (10YR 4/3) moist; moderate medium prismatic structure parting to moderate medium subangular blocky; slightly hard, very friable, slightly sticky and nonplastic; many very fine and fine roots; many very fine and fine interstitial pores; 15 percent cobbles, 30 percent gravel; slightly acid (pH 6.4); gradual wavy boundary. (8 to 16 inches thick)

Bw2--23 to 31 inches; brown (10YR 5/3) very cobbly loam, brown (10YR 4/3) moist; weak coarse subangular blocky structure; slightly hard, very friable, nonsicky and nonplastic; common very fine and fine roots and few medium roots; common very fine and fine interstitial pores; 30 percent cobbles, 30 percent gravel; slightly acid (pH 6.4); clear wavy boundary. (5 to 14 inches thick)

R--31 inches; hard, slightly fractured, fine grained igneous bedrock.

TYPE LOCATION: Jefferson County, Montana; 650 feet south and 400 feet west of the NE corner of sec. 1, T. 3 N., R. 4 W.

RANGE IN CHARACTERISTICS:

Soil temperature - 36 to 40 degrees F.
Mollic epipedon thickness - 7 to 14 inches
Depth to a lithic contact - 20 to 40 inches

A horizons
Hue: 2.5Y or 10YR; dry or moist
Value: 3 or 4 dry; 2 or 3 moist
Clay content: 18 to 27 percent
Rock fragments: 15 to 50 percent--10 to 35 percent gravel or channers, 0 to 15 percent cobbles, stones and boulders
Reaction: pH 6.1 to 6.8

Bw1 horizon
Hue: 2.5Y or 10YR; dry or moist
Value: 5 or 6 dry; 4 or 5 moist
Chroma: 2 or 3; dry or moist
Texture: loam or sandy clay loam
Clay content: 18 to 27 percent
Rock fragments: 35 to 60 percent--25 to 40 percent gravel or channers, 10 to 30 percent cobbles
Reaction: pH 6.1 to 6.8

Bw2 horizon
Hue: 7.5YR, 10YR or 2.5Y; dry or moist
Value: 5 or 6 dry; 4 or 5 moist
Chroma: 2 or 3; dry or moist
Texture: loam, sandy clay loam, or sandy loam
Clay content: 18 to 27 percent
Rock fragments: 35 to 80 percent--30 to 50 percent gravel or channers, 5 to 30 percent cobbles
Reaction: pH 6.1 to 6.8

COMPETING SERIES:
Antrobus (CO) - are very deep
Grafen (CO) - do not have a lithic contact above 40 inches
Greyback (WY) - are very deep
Handran (CO) - are very deep
Maurice (MT) - are very deep
Mccort (WY) - are very deep
Midelight (WY) - are deep to a lithic contact
Parachute (CO) - have a BC horizon
Sebud (MT) - are very deep
Supervisor (NM) - do not have a cambic horizon
Teemat (WY) - are very deep
Thornburgh (CO) - are very deep
Tiban (MT) - are very deep
Tineman (WY) - are very deep
Vanwirt (CO) are very deep

GEOGRAPHIC SETTING:
Landform - escarpments, ridges and mountain slopes
Elevation - 5,500 to 8,000 feet
Slope - 2 to 60 percent
Parent material - slope alluvium and colluvium over residuum derived from hard fine grained igneous or metamorphic rock
Climate - long, cold winters; cool, moist springs; short, cool summers
Mean annual precipitation - 15 to 24 inches
Mean annual air temperature - 36 to 40 degrees F.
Frost-free period - 30 to 70 days

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Arrowpeak and Sebud soils. Arrowpeak soils are shallow and on more convex postions. Sebud soils are very deep and on slightly more concave postions.

DRAINAGE AND PERMEABILITY: Well drained, moderate permeability.

USE AND VEGETATION: Surdal soils are primarily used for rangeland, wildlife habitat and watershed. The potential native vegetation is mainly Idaho fescue, rough fescue, Richardson needlegrass, Columbia needlegrass, parry danthonia, mountain brome, lupine, sticky geranium, hoods phlox and big sagebrush.

DISTRIBUTION AND EXTENT: Surdal soils are of moderate 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 0 to 13 inches (A1, A2 horizons)
Cambic horizon - from 13 to 31 inches (Bw1, Bw2 horizons)
Lithic contact - at 31 inches (R horizon)
Particle-size control section - from 10 to 31 inches (A2, Bw1, Bw2 horizons

Surdal soils have a cryic temperature regime and an ustic moisture regime.

Additional Data: Soil interpretation record - MT3056.

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National Cooperative Soil Survey
U.S.A.