LOCATION GWIN                    WA+ID OR

Established Series
Rev. PNP/KDPL/SBC
09/2019

GWIN SERIES

Landscape--basalt plateaus, hills, canyonlands
Landform--structural benches, ridgetops, hillslopes, canyons
Slope--0 to 90 percent
Parent material--colluvium and residuum derived from basalt mixed with loess
Mean annual precipitation--about 510 mm
Mean annual air temperature--about 9 degrees C
Depth class--shallow
Drainage class--well drained
Soil moisture regime--xeric
Soil temperature regime--mesic
Soil moisture subclass--typic

TAXONOMIC CLASS: Loamy-skeletal, mixed, superactive, mesic Lithic Argixerolls

TYPICAL PEDON: Gwin cobbly silt loam in an area of rangeland

A--0 to 13 cm; cobbly silt loam, dark grayish brown (10YR 4/2) dry, very dark brown (10YR 2/2) moist; moderate to strong granular structure and weak thin platy; slightly hard, friable, slightly sticky and slightly plastic; many roots; 20 percent angular rock fragments; neutral (pH 6.6); clear smooth boundary

Bt1--13 to 30 cm; very cobbly silty clay loam, dark grayish brown (10YR 4/2) dry, very dark brown (10YR 2/2) moist; moderate coarse prismatic structure and moderate coarse subangular blocky; hard, firm, moderately sticky and moderately plastic; many roots; many fine continuous tubular pores; few faint clay films on vertical and horizontal faces of peds; 55 percent angular rock fragments; neutral (pH 6.6); gradual wavy boundary

Bt2--30 to 43 cm; extremely cobbly silty clay loam, brown (7.5YR 4/2) dry, dark brown (7.5YR 3/2) moist; moderate medium subangular blocky structure; hard, firm, moderately sticky and moderately plastic; few roots; few faint black (10YR 2/1) clay films on faces of peds and rock fragments; 60 percent angular rock fragments; neutral (pH 6.6); gradual wavy boundary

R--43 cm; basalt

TYPE LOCATION: Walla Walla County, Washington, on Black Snake Ridge; in the SW1/4SW1/4 of section 3, T. 7 N., R. 38 E.

RANGE IN CHARACTERISTICS:
Mean annual soil temperature--about 8 to 12 degrees C
Moisture control section--usually moist; typically dry 45 to 75 consecutive days following summer solstice
Depth to bedrock--25 to 50 cm
Particle-size control section--40 to 90 percent gravel, cobbles, and stones; 15 to 35 percent clay
Reaction--6.1 to 7.8
Hue--10YR or 7.5YR throughout

A horizon
Value--3 to 5 dry, 2 or 3 moist
Chroma--1 to 6 dry, 1 to 3 moist
Thickness--5 to 20 cm

Bt horizon
Value--3 to 6 dry, 2 to 4 moist
Chroma--1 to 6 dry, 1 to 4 moist
Texture--silt loam, loam, clay loam, silty clay loam
Rock fragment content--35 to 90 percent
Combined thickness--10 to 45 cm

COMPETING SERIES:
Canfire, Chinabutte--dry 75 to 90 consecutive days following summer solstice
Clovercreek--dominantly greenstone gravel
Shepridge--formed in colluvium or alluvium over residuum derived from quartzite
Stepmount--secondary carbonates at a depth of 25 to 45 cm
Windry--dry 90 to 100 consecutive days following summer solstice

GEOGRAPHIC SETTING:
Elevation--490 to 1375 cm in Washington, 240 to 1900 cm in Oregon and Idaho; highest elevations on south aspects only
Climate--cool, wet winters; hot, dry summers
Mean annual precipitation--360 to 840 mm
Mean January air temperature--about -4 to -2 degrees C
Mean July air temperature--about 19 to 22 degrees C
Mean annual air temperature--about 6 to 11 degrees C
Frost-free season--90 to 180 days

GEOGRAPHICALLY ASSOCIATED SOILS:
Athena--no lithic contact within a depth of 150 cm or more
Balder--no argillic horizon; 25 to 50 cm (shallow) to a paralithic contact (volcanic tuff)
Couse--no lithic contact within a depth of more than 150 cm
Klicker--50 to 100 cm (moderately deep) to a lithic contact (basalt)
Palouse--no lithic contact within a depth of 100 to 150 cm or more
Rockly--argillic horizon; 10 to 30 cm (very shallow, shallow) to a lithic contact (basalt)

DRAINAGE AND SATURATED HYDRAULIC CONDUCTIVITY:
Drainage class--well drained
Saturated hydraulic conductivity (Ksat)--moderately high

USE AND VEGETATION:
Use--livestock grazing, wildlife habitat
Native vegetation--mainly bluebunch wheatgrass, Idaho fescue, and Sandberg bluegrass

DISTRIBUTION AND EXTENT: Eastern and central Washington, eastern Oregon, and western Idaho; MLRAs 8, 9, and 10; large extent

SOIL SURVEY REGIONAL OFFICE (SSRO) RESPONSIBLE: Portland, Oregon

SERIES ESTABLISHED: Walla Walla County, Washington; 1960

REMARKS:
Diagnostic horizons and other features recognized in this pedon
*Mollic epipedon--zone from the surface to a depth of 43 cm
*Argillic horizon--zone from 13 to 43 cm
*Depth to lithic contact--43 cm
*Particle-size control section--zone from 13 to 43 cm

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National Cooperative Soil Survey
U.S.A.