LOCATION KOYUKUK                 AK

Established Series
Rev. BEK/JPM/DLM
05/2022

KOYUKUK SERIES

Depth class: very deep
Drainage class: well drained
Parent material: loess over alluvium and/or glaciofluvial deposits and/or eolian sands
Landform: terraces, sandy hills, glacial plains covered with thick loess layer
Slopes: 0 to 50 percent
Mean annual temperature: about 24 degrees F., -4.4 C.
Mean annual precipitation: about 13 inches, 330 mm

TAXONOMIC CLASS: Coarse-silty, mixed, superactive Typic Haplocryepts

TYPICAL PEDON: Koyukuk silt loam -- on a nearly level slope under forest vegetation. (All colors are for moist soil)

Oi--0 to 2 inches, (0 to 5 cm): slightly decomposed forest litter; many roots; moderately acid (pH 5.6); abrupt smooth boundary. (1 to 6 inches thick)

A--2 to 3 inches, (5 to 8 cm); dark brown (10YR 3/3) silt loam; weak very fine granular structure; very friable, nonsticky and nonplastic; many roots; moderately acid (pH 5.6); abrupt wavy boundary. (1 to 4 inches thick)

Bw--3 to 13 inches, (8 to 33 cm); brown (10YR 4/3) silt loam with black (10YR 2/1) horizontal streaks of highly decomposed organic matter and charcoal; weak thin platy structure; very friable, nonsticky and nonplastic; common roots; moderately acid (pH 5.8); clear wavy boundary. (8 to 14 inches thick)

BC--13 to 25 inches, (33 to 64 cm); yellowish brown (10YR 5/4) and strong brown (7.5YR 5/6) silt loam; weak thin platy structure; very friable, nonsticky and nonplastic; common roots; few black (10YR 2/1) stains and concretions; slightly acid (pH 6.1); clear wavy boundary. (11 to 20 inches thick)

C1--25 to 44 inches, (64 to 112 cm); grayish brown (2.5Y 5/2) silt loam; weak thin platy structure; very friable, nonsticky and nonplastic; few roots; slightly acid (pH 6.2); abrupt smooth boundary. (18 to 22 inches thick)

2C2--44 to 60 inches, (112 to 152 cm); yellowish brown (10YR 5/4) very gravelly sand; single grain; loose, nonsticky and nonplastic; slightly acid (pH 6.4).

TYPE LOCATION: Totchaket Area, Alaska; in the NE 1/4 of the NE 1/4 of Section 30, T.4S., R.9W., Fairbanks Meridian.

RANGE IN CHARACTERISTICS:
Solum thickness: 9 to 24 inches, 23 to 61 cm
Loess mantle: moderate content of mica, but less than 25 percent
Particle size control section: weighted average particle size less than 15 percent fine sand or coarser and less than 18 percent clay; horizontal streaks of finely divided organic matter and charcoal commonly are present
Reaction: strongly acid to neutral throughout the profile
A horizon:
Matrix color: hue of 7.5YR to 2.5Y; value of 3 or 4; chroma of 2 to 4
Texture: silt loam or very fine sandy loam

B horizon:
Matrix color: hue of 7.5YR to 2.5Y; value of 3 to 6; chroma of 2 to 6
Texture: silt loam, silt, or very fine sandy loam
Concretions: brown and black concretions are common in the lower part in some horizons.

C horizon:
Matrix color: hue of 10YR to 5Y; value of 4 to 6; chroma of 1 to 6
Texture: silt loam or very fine sandy loam

2C horizon:
Matrix color: hue of 10YR to 5Y; value of 4 to 6; chroma of 1 to 6
Texture: silt loam, loam, very fine sandy loam, fine sandy loam, sandy loam, loamy sand, or sand modified by 0 to 50 percent total coarse fragments; 0 to 50 percent gravel, 0 to 10 percent cobbles

COMPETING SERIES: These are the Bodenburg, Fairless, Fairbanks, Nunaniq, and Toghotthele series in the same family. Bodenburg soils do not have substantial mica content in the control section. Fairless soils do not have thin fine textured lamellae in parts of the solum. Fairbanks soils have less than 15 percent fine sands and coarser in the substratum. Nunaniq soils are presumed to have warmer soil temperatures. Toghotthele soils have calcium carbonate in the substratum.

GEOGRAPHIC SETTING:
Parent material: loess over alluvium and/or glaciofluvial deposits and/or eolian sands
Landform: terraces, sandy hills, glacial plains covered with thick loess layer
Slopes: 0 to 50 percent
Climate: subarctic continental with long, cold winters and short, warm summers Mean annual temperature: 24 to 30 degrees F., -4.4 to -1 C.
Mean annual precipitation: 10 to 15 inches, 254 to 381 mm

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Batza and Kuskokwim soils. Batza soils are on dominantly north facing footslopes, are mottled and have a perennially frozen substratum. Kuskokwim soils have a thick organic mat and are shallow to permafrost.

DRAINAGE AND PERMEABILITY: Well drained, low to high runoff, moderately high to high saturate hydraulic conductivity in the loess mantle and moderately high to very high in lower part of the substratum.

USE AND VEGETATION: The soils are almost entirely under forest dominated by white spruce, paper birch, and quaking aspen. When cleared, most areas are suitable for small grains, grasses, and vegetables.

DISTRIBUTION AND EXTENT: MLRA 229 Interior Alaska Lowlands. The series is of moderate extent.

SOIL SURVEY REGIONAL OFFICE (SSRO) RESPONSIBLE: WASILLA, ALASKA

SERIES ESTABLISHED: Totchaket Area, Alaska, 1978.

REMARKS: Diagnostic horizons and features recognized in this profile include: Ochric epipedon: 2 to 3 inches, 5 to 8 cm
Cambic horizon: 3 to 13 inches, 8 to 33 cm
Particle size Control section: less than 15 percent fine sand or coarser and less than 18 percent clay from 2 to 42 inches, 5 to 107 cm
Temperature regime: cryic
Moisture regime: udic

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National Cooperative Soil Survey
U.S.A.