LOCATION STIBNITE AK

Established Series
SDB/MJS
08/2025

STIBNITE SERIES

Depth class: very deep
Drainage class: well drained
Parent material: organic material over coarse-loamy till
Landscape: foothills and mountains
Landform: kame moraines, mountain slopes, till plains, and kettles
Slope: 4 to 60 percent
Mean annual precipitation: about 600 mm (24 in)
Mean annual air temperature: about -3 degrees C (27 F)
Frost-free period: 32 to 103 days

TAXONOMIC CLASS: Coarse-loamy, mixed, superactive, nonacid, subgelic Typic Haplogelepts

TYPICAL PEDON: Stibnite silt loam in a lichen dominated community on a south facing concave, concave toeslope on a slope of 4% at an elevation of 1032 m (3385 ft).

Oe--0 to 6 cm (0 to 2 in); moderately decomposed plant material, dark brown (7.5YR 3/3) dry, very dark brown (7.5YR 2.5/3) moist; many very fine and fine roots throughout; strongly acid (pH 5.3); clear smooth boundary (2 to 8 cm, 1 to 3 in)

A--6 to 18 cm (2 to 7 in); silt loam, very dark grayish brown (10YR 3/2) moist; moderate medium subangular blocky structure; soft, very friable, slightly sticky, slightly plastic; common very fine and fine roots throughout; very fine and fine dendritic tubular pores; strongly acid (pH 5.2); clear wavy boundary (4 to 19 cm, 2 to 7 in)

Bw--18 to 34 cm (7 to 13 in); loam, dark yellowish brown (10YR 3/4) moist; weak medium subangular blocky structure; soft, very friable, slightly sticky, slightly plastic; few very fine and fine roots throughout; very fine and fine dendritic tubular pores; 5 percent gravel by volume; moderately acid (pH 5.6); gradual wavy boundary (13 to 39 cm, 5 to 15 in)

BC--34 to 150 cm (13 to 59 to in); sandy loam, dark olive brown (2.5Y 3/3) moist; weak fine granular structure; soft, very friable, slightly sticky, slightly plastic; few very fine roots throughout; interstitial pores; 8 percent gravel by volume; strongly acid (pH 5.3). (85 to 131 cm, 33 to 52 in)

TYPE LOCATION: North Copper River Soil Survey Area, Alaska; latitude 63.07123, longitude -145.58508, UTM 6994313.01 north and UTM 571490.34 east, zone 6, Datum WGS84.

RANGE IN CHARACTERISTICS:

Soil moisture regime: udic
Soil temperature regime: cryic
Mean annual soil temperature: -4 to -2 degrees C. (25 to 28 degrees F)
Thickness of organic material: 2 to 8 cm (1 to 3 in)
Thickness of epipedon: 6 to 27 cm (2 to 11 in)
Thickness of cambic horizon: 15 to 38 cm (6 to 15 in)

Oi, Oe, Oa example horizon:
Hue: 7.5YR or 10YR
Value: 2 to 3
Chroma: 1 to 3
Texture: Slightly decomposed organic material, moderately decomposed organic material, highly decomposed organic material.
Organic matter: 60 to 90 percent
Reaction class: very strongly acid to strongly acid (pH 4.8 to 5.6)

A horizon:
Hue: 7.5YR or 10YR
Value: 2 to 3
Chroma: 1 to 2
Texture: silt loam
Sand: 15 to 40 percent
Silt: 52 to 77 percent
Clay: 8 to 15 percent
Rock fragments: 0 to 8 percent gravels
Organic matter: 4 to 10 percent
Reaction class: very strongly acid to slightly acid (pH 5.0 to 6.1)

Bw horizon:
Hue: 10YR or 2.5Y
Value: 3 to 5
Chroma: 2 to 4
Texture: loam, gravelly loam
Sand: 35 to 50 percent
Silt: 32 to 50 percent
Clay: 10 to 18 percent
Rock fragments: 3 to 25 percent gravels
Organic matter: 1 to 3 percent
Reaction class: strongly acid to neutral (pH 5.2 to 6.8)

BC or C horizon:
Hue: 10YR or 2.5Y
Value: 3 to 4
Chroma: 2 to 4
Texture: sandy loam, gravelly sandy loam
Sand: 50 to 75 percent
Silt: 12 to 45 percent
Clay: 5 to 16 percent
Rock fragments: 5 to 20 percent gravels
Organic matter: 0.1 to 1.0 percent
Reaction class: very strongly acid to slightly acid (pH 5.0 to 6.2)

COMPETING SERIES: There are no competing series.

GEOGRAPHIC SETTING:
Elevation: 600 to 1600 meters (1970 to 5250 ft)
Parent material: organic material over coarse-loamy till
Landform: Landform: kame moraines, mountain slopes, till plains, and kettles
Slopes: 5 to 60 percent
Mean annual precipitation: 400 to 800 mm (16 to 31 in)
Mean annual air temperature: -4 to -2 degrees C. (25 to 28 degrees F)
Frost-free period: 32 to 103 days

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Ahtell, Cirquecreek, Haleycreek, Ottaway, Ride, and Tsina series.
Ahtell soils have folistic and umbric epipedons and occur on hill tops and hillside positions.
Cirquecreek soils are well drained, have a cambic horizon, and occur on saddles and mountain slopes
Haleycreek soils have a mollic epipedon and occur on hillslopes of mountains and river valleys.
Ottoway soils have permafrost between 50 and 100cm (20 to 39 in), have a mollic epipedon, form on slopes over 25 percent, and occur on hills and mountain slopes.
Ride soils are somewhat excessively drained, have a cambic horizon, and occur on mountain slopes and hillslopes.
Tsina soils are extremely flaggy starting at a depth of 10 to 38 cm (4 to 15 in), and occur on mountain slopes above 800 m (2600ft) elevation.

DRAINAGE AND SATURATED HYDRAULIC CONDUCTIVITY:
Drainage class: well drained
Saturated Hydraulic Conductivity: very high in the Oi horizon, moderately high in the A horizon, high in the Bw and BC horizons.
Permeability: very rapid in the Oi horizon, moderate in the A horizon, rapid in the Bw and BC horizons.

Runoff: high

USE AND VEGETATION:
Use: wildlife habitat, recreation, and subsistence
Native vegetation: lichen, moss, willow

DISTRIBUTION AND EXTENT: MLRA 228 Interior Alaska mountains.
Extent: moderate

SOIL SURVEY REGIONAL OFFICE (SSRO) RESPONSIBLE: Wasilla, Alaska

SERIES ESTABLISHED: North Copper River Soil Survey, Alaska, 2024.

REMARKS: Diagnostic features and horizons recognized in this profile include:

Particle-size control section: 31 to 106 cm (12 to 42 in)

Ochric epipedon: 0 to 12 cm (0 to 5 in) (Oi, A horizon)

Cambic horizon: 18 to 34 cm (7 to 13 in) (Bw horizon)

ADDITIONAL DATA:

User pedon Id: 2023AK261288

National Cooperative Soil Survey
U.S.A.