LOCATION TWIN AK
Established Series
JDP/NDP/TJR
02/2022
TWIN SERIES
Landscape--alluvial plains
Landform--stream terraces
Slope--0 to 3 percent
Parent material--alluvium
Mean annual precipitation--about 255 mm
Mean annual air temperature--about -6 degrees C
Depth class--very deep
Drainage class--poorly drained
Soil moisture regime--aquic
Soil temperature regime--gelic
Soil moisture subclass--typic
TAXONOMIC CLASS: Coarse-silty, mixed, superactive, nonacid, subgelic Typic Aquorthels
TYPICAL PEDON: Twin silt loam on a woodland terrace with a slope of 1 percent and an elevation of 105 m (The soil was moist throughout when described on August 31, 2015.)
Oi--0 to 5 cm; slightly decomposed plant material; many very fine and medium roots, common fine, coarse, and very coarse roots; strongly acid (pH 5.5); abrupt smooth boundary
Oa--5 to 11 cm; highly decomposed plant material; common very fine, fine, medium and coarse roots; slightly acid (pH 6.3); abrupt smooth boundary
C--11 to 40 cm; silt loam; 75 percent light brownish gray (2.5Y 6/2) dry, dark grayish brown (2.5Y 4/2) moist and 25 percent grayish brown (10YR 5/2) dry, very dark grayish brown (10YR 3/2) moist; weak thick platy structure; slightly hard, friable, nonsticky and nonplastic; common very fine, fine, and medium roots; few fine and medium pores; 15 percent yellowish brown (10YR 5/6) moist, masses of oxidized iron in matrix; noneffervescent; slightly alkaline (pH 7.7); clear irregular boundary
Cg--40 to 62 cm; silt loam; gray (2.5Y 6/1) dry, dark gray (2.5Y 4/1) moist; massive; slightly hard, friable, nonsticky and nonplastic; 25 percent gray (2.5Y 5/1) moist, iron depletions in matrix and 40 percent light olive brown (2.5Y 5/6) moist, masses of oxidized iron in matrix; strongly effervescent; slightly alkaline (pH 7.8); clear smooth boundary
Cgf--62 to 100 cm; silt loam; gray (5Y 6/1) dry, dark gray (5Y 4/1) moist; massive; moderately hard, firm, nonsticky and nonplastic; strongly effervescent; slightly alkaline (pH 7.7)
TYPE LOCATION: Yukon-Koyukuk Census Area, Alaska; latitude 66.3095500 degrees, longitude -148.1398800 degrees, datum WGS84 (coordinates determined with a GPS)
RANGE IN CHARACTERISTICS:
Mean annual soil temperature-- -4 to 1 degrees C
Depth to permafrost--50 to 90 cm
Depth to redoximorphic features--15 to 50 cm
Oi and Oa horizons
Combined thickness--10 to 18 cm
Reaction--5.5 to 7.5
Oe horizon (where present)
Combined thickness--10 to 18 cm
Reaction--5.5 to 7.5
A horizon (where present)
Hue--10YR, 2.5Y
Value--2 to 4 moist, 4 to 6 dry
Chroma--1 or 2 moist
Fine-earth texture--silt loam, very fine sandy loam, silt
Clay content--0 to 18 percent
Reaction--6.0 to 7.5
Effervescence--none
Thickness--5 to 15 cm
C and Cg horizons
Hue--10YR, 2.5Y
Value--3 or 4 moist, 5 or 6 dry
Chroma--1 or 2 moist
Fine-earth texture--silt loam, very fine sandy loam
Clay content--0 to 18 percent
Reaction--7.0 to 8.5
Effervescence--none to strong
Combined thickness--40 to 80 cm
Cgf horizon
Value--2 to 4 moist, 4 to 6 dry
Chroma--1 or 2 moist
Fine-earth texture--silt loam, very fine sandy loam
Clay content--0 to 18 percent
Reaction--7.0 to 8.5
Effervescence--none to strong
Thickness--60 to 100 cm
COMPETING SERIES:
Chetlechak--occasional flooding; lower positions on similar landforms
Pitka--no flooding; scrubland depressions on adjacent terraces
Dotlake--interdunes with sandy substrata; higher mean annual precipitation
GEOGRAPHIC SETTING:
Elevation--90 to 300 m
Climate--short, warm summers and long, very cold winters
Mean annual precipitation--210 to 310 mm
Mean annual air temperature-- -12 to 0 degrees C
Frost-free period--45 to 97 days
GEOGRAPHICALLY ASSOCIATED SOILS:
Jokinaugh--aquic conditions within 25 cm with frequent ponding; no permafrost; depressions on similar landforms
Theodore--aquic conditions within 100 cm; no permafrost; adjacent flood plains
Kingslough--no aquic conditions within 150 cm; adjacent flood plains
Chetlechak--aquic conditions within 50 cm with occasional flooding; depressions on similar landforms
DRAINAGE AND SATURATED HYDRAULIC CONDUCTIVITY:
Drainage class-- poorly drained
Saturation in normal years--water table top depth between a depth of 13 to 50 cm in June, and saturated below a depth of 50 cm throughout the rest of the year
Flooding--rare
Ponding--none
Saturated hydraulic conductivity (Ksat)--high throughout
USE AND VEGETATION:
Use--wildlife habitat, subsistence, recreation
Potential natural vegetation--white spruce, black spruce, resin birch, lingonberry, grayleaf willow, red fruit bearberry, prickly rose, black crowberry, bog blueberry, bog Labrador tea, littletree willow, shrubby cinquefoil, shrub birch, sedge, bluejoint, dwarf scouringrush, felt lichen, greygreen reindeer lichen, cup lichen, stairstep moss
DISTRIBUTION AND EXTENT: Yukon Flats Lowlands, Alaska; MLRA 232; moderate extent
SOIL SURVEY REGIONAL OFFICE (SSRO) RESPONSIBLE: WASILLA, ALASKA
SERIES ESTABLISHED: Yukon Flats National Wildlife Refuge, Yukon-Koyukuk Census Area, Alaska; 2020
REMARKS:
Diagnostic horizons and other features in this pedon
*Particle-size control section--zone from 36 to 111 cm
*Ochric epipedon
*Redoximorphic iron concentrations--C and Cg horizons
*Redoximorphic iron depletions with chroma of 2 or less--C and Cg horizons
*Reduced matrix--Cg and Cgf horizons
*Aquic conditions--C, Cg, and Cgf horizons
*Permafrost--Cgf horizon
National Cooperative Soil Survey
U.S.A.