LOCATION GEMSON ID+UT
Established Series
Rev. WJL
01/2023
GEMSON SERIES
The Gemson series is a member of the fine, montmorillonitic, mesic family of Calcic Argixerolls. Typically, Gemson soils have dark grayish brown, platy, neutral, cobbly clay loam A1 horizons that grade into dark brown, prismatic and angular blocky, neutral clay overlying horizons with accumulation of carbonates.
TAXONOMIC CLASS: Fine, smectitic, mesic Calcic Argixerolls
TYPICAL PEDON: Gemson very cobbly clay loam - rangeland. (Colors are for dry soils unless otherwise noted.)
A11--0 to 2 inches; dark grayish brown (10YR 4/2), very cobbly light clay loam containing about 15 percent angular gravel; very dark brown (10YR 2/2) moist; moderate very fine platy, parting to strong or moderate, very fine granular structure; slightly hard, very friable, slightly sticky, slightly plastic; common very fine and fine roots; many very fine interstitial pores; noncalcareous; slightly alkaline (pH 7.4); clear smooth boundary. (2 to 8 inches thick)
A12--2 to 8 inches; dark grayish brown (10YR 4/2), cobbly clay loam, very dark brown (10YR 2/2) moist; weak fine subangular blocky, parting to strong, fine and medium granular structure; slightly hard, very friable, sticky, plastic; common very fine and fine, few very fine interstitial and very fine tubular pores; few very thin clay films on peds; noncalcareous; slightly alkaline (pH 7.4); clear wavy boundary. (3 to 7 inches thick)
B21t--8 to 15 inches; brown (7.5YR 4/3) clay, dark brown (7.5YR 3/2) moist; dark brown (7.5YR 4/2) coating on peds; moderate coarse prismatic, parting to strong coarse and medium angular blocky structure; extremely hard, extremely firm, very sticky, very plastic; few very fine, fine and medium roots; few very fine pores; medium continuous clay films on peds; few uncoated silt grains on peds; noncalcareous; slightly alkaline (pH 7.8); clear wavy boundary. (5 to 9 inches thick)
B22t--15 to 24 inches; brown (7.5YR 5/3) clay, dark brown (7.5YR 4/3) moist; dark reddish gray (5YR 4/2) coating on peds, dark reddish brown (5YR 3/3) moist; moderate coarse prismatic, parting to strong medium and coarse angular blocky structure; extremely hard, very firm, very sticky, very plastic; few very fine, fine and medium roots in the cracks; few very fine pores; dense; medium continuous clay films on peds; few medium distinct lime splotches, matrix noncalcareous; moderately alkaline (pH 8.1); gradual wavy boundary. (5 to 12 inches thick)
B23tca--24 to 37 inches; brown (7.5YR 5/3) clay, dark brown (7.5YR 4/3) moist; dark reddish gray (5YR 4/2) coating on peds; weak coarse prismatic, parting to strong medium angular blocky structure; very hard, very firm, very sticky, very plastic; few fine and medium roots in the cracks; medium continuous clay films on peds; common medium distinct lime splotches on and in peds, matrix mostly slightly calcareous; moderately alkaline (pH 8.2); clear wavy boundary. (6 to 15 inches thick)
B31tca--37 to 50 inches; brown (7.5YR 5/3) clay loam, dark brown (7.5YR 4/3) moist; reddish brown (5YR 4/3) coating on peds; moderate fine subangular blocky structure; hard, friable, sticky, plastic; few medium and fine roots; common very fine pores; thin patchy clay films on peds; many lime veins and splotches on peds, matrix mostly slightly calcareous; moderately alkaline (pH 8.3); clear wavy boundary.
B32ca--50 to 65 inches; brown (7.5YR 5/3) angular gravelly clay loam containing few cobblestones; dark brown (7.5YR 4/3) moist; moderate very fine and fine subangular and angular blocky structure; hard, friable, sticky, plastic; few fine roots; common very fine tubular pores; thin patchy clay films on peds; slightly calcareous and common lime veins; moderately alkaline (pH 8.0); clear wavy boundary. (0 to 18 inches thick)
B33tca--65 to 67 inches; little material similar to the B32tca horizon in the cracks between the basalt fragments; vesicular basalt fragments coated with light brown (7.5YR 6/4) clay films (5YR 5/4 moist) and common lime veins and splotches; moderately alkaline (pH 8.1).
TYPE LOCATION: Northwest Hydrology Research Watershed, Reynolds Creek, Owyhee County, Idaho; about 5.4 miles northwest of Reynolds School on the west side of the new road above the Boston ranch (turning west at the Boston gate) and 1.5 miles northward by road from the creek crossing; southeast 1/4, southwest 1/4 of section 3, T. 2 S., R. 4 W.
RANGE IN CHARACTERISTICS: The depth to bedrock ranges from 45 inches to many feet. The mollic epipedon is 10 to 20 inches thick. The solum is 40 to 70 inches thick. Angular gravel, cobblestones, and stones in the solum range from about 3 to 20 percent by volume and are mainly of basalt. The mean annual soil temperature is 47 degrees to 53 degrees F., and the mean summer soil temperature is 65 degrees to 70 degrees F. When not frozen, some subhorizon of the soil between depths of 10 and 40 inches is dry for 90 cumulative days or more. The A1 horizon has value of 4 to 4.8 dry and 2 to 2.8 moist and chroma of 1.6 to 2.5. The combined thickness of the A horizons is 6 to 14 inches. The B2t horizon has chroma of 2 or 3. It is clay, silty clay, or heavy clay loam, containing 35 to 50 percent clay. It has moderate medium to very coarse prismatic to strong medium and coarse angular blocky structure. The argillic horizon has a clay increase of less than 20 percent total clay within a 3-inch vertical distance from its top. The accumulation of calcium carbonate is weak to moderate. Probably the base saturation of the argillic horizon is above 80 percent.
COMPETING SERIES: These are the
Durkee,
Flowell,
Gem, Gemid,
Newell,
Oxford,
Reardan, and
Ruclick series. Durkee soils have strong prismatic B2t horizons, sola 14 to 24 inches thick and are underlain by argillite bedrock. Flowell soils have sola 12 to 38 inches thick. Gem and Gemid soils have a lithic contact at depths of 20 to 40 inches. Also, Gemid soils have mean annual soil temperature of less than 47 degrees F. Newell soils have moderately fine textured B2t horizons. Oxford soils have 2.5Y or 5YR hue in the Bt horizon. Reardan soils have a B&A horizon. Ruclick soils have more than 50 percent coarse fragments in the Bt horizon and have a lithic contact at depths of less than 40 inches.
GEOGRAPHIC SETTING: The soils are on level to steep alluvial fans and colluvial footslopes and other parts of uplands at elevations of about 2,500 to 5,000 feet. Slopes are mostly between 5 and 35 percent and range from 0 to 50 percent. The soils formed in alluvium and colluvium from basaltic materials. The climate is dry subhumid and has dry summers. Mean annual precipitation is 12 to 16 inches, including 3 to 5 feet of snowfall. Average freeze-free period is 120 to 160 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the
Bakeoven,
Gross,
Lickskillet,
Reywat, and
Yergenson soils and the competing
Newell and
Gem soils. Bakeoven, Gross, Lickskillet, Reywat, and Yergenson soils have a moderately fine or medium textured B2t horizon.
DRAINAGE AND PERMEABILITY: Well drained; medium to rapid runoff; slow permeability.
USE AND VEGETATION: Nearly all of the soils are used for range. The natural vegetation is mainly bluebunch wheatgrass, Sandberg bluegrass, cheatgrass, big sagebrush, bitterbrush, rabbitbrush, wild buckwheat, lupine, and Indian paintbrush.
DISTRIBUTION AND EXTENT: About 1 square mile is mapped in the Reynolds Creek Watershed. The series is inextensive, with 5,000 to 10,000 acres likely in other parts of southwestern Idaho (Owyhee, Elmore, Boise, and Washington counties) and nearby States.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Phoenix, Arizona
SERIES ESTABLISHED: Owyhee County, Idaho, 1969.
REMARKS: The Gemson soils were classified formerly as Chestnut soils.
National Cooperative Soil Survey
U.S.A.