LOCATION GEM ID+OREstablished Series
TAXONOMIC CLASS: Fine, smectitic, mesic Calcic Argixerolls
TYPICAL PEDON: Gem silty clay loam - grass and sagebrush. (Colors are for dry soil unless otherwise noted.)
A1--0 to 3 inches; dark grayish brown (10YR 4/2) loam, very dark brown (10YR 2/2) moist; when dry vertical cracks form very thick 4- to 6-sided blocky plates 4 to 7 inches across, which part to moderate thin plates, then to moderate fine granular structure; very hard, friable, sticky and plastic; common very fine roots; few very fine pores; 7 percent angular basalt gravel; neutral (pH 6.6); abrupt wavy boundary. (2 to 5 inches thick)
A2--3 to 6 inches; very dark grayish brown (10YR 3/2) silty clay loam, very dark brown (7.5YR 2/2) moist; main vertical cracks as above with some secondary cracks 2 inches apart; weak medium platy structure that parts to moderate very fine subangular blocky; hard, firm, sticky and plastic; common very fine roots; few very fine pores; 4 percent angular basalt gravel; slightly acid (pH 6.4); abrupt wavy boundary. (2 to 5 inches thick)
BA--6 to 9 inches; dark brown (7.5YR 4/2) silty clay loam, dark brown (7.5YR 3/2) moist; moderate coarse prismatic structure that parts to weak medium, fine, and very fine angular blocky; very hard, very firm, sticky and very plastic; common very fine roots; few very fine pores; 3 percent angular basalt gravel; many prominent dark brown (7.5YR 4/2) clay films on faces of peds; streaks and tongues of material similar to A2 horizon; slightly acid (pH 6.5); clear wavy boundary. (0 to 9 inches thick)
Bt1--9 to 15 inches; brown (7.5YR 4/2) heavy silty clay loam, dark brown (7.5YR 3/3) moist; moderate coarse prismatic structure that parts to moderate fine and very fine angular blocky; very hard, very firm, sticky and very plastic; few very fine roots; few very fine pores; 4 percent fine gravel and few very coarse sand particles; many prominent clay films on faces of peds; neutral (pH 6.6); clear wavy boundary. (4 to 9 inches thick)
Bt2--15 to 20 inches; brown (10YR 5/3) heavy clay loam, dark brown (7.5YR 4/3) moist; weak medium prismatic structure that parts to moderate fine angular blocky; very hard, firm, sticky and very plastic; few very fine roots; few very fine pores; krotovina 2 inches across; 6 percent angular fine gravel and few very coarse sand grains; many prominent clay films on faces of peds; neutral (pH 6.7); clear wavy boundary. (4 to 9 inches thick)
BCt--20 to 23 inches; brown (10YR 5/3) light clay loam, dark brown (7.5YR 4/3) moist; weak medium prismatic structure that parts to moderate fine angular blocky; very hard, firm, sticky and plastic; few very fine roots; common fine pores; 5 percent fine basalt gravel; many faint clay films on faces of peds; neutral (pH 6.9); abrupt wavy boundary. (0 to 5 inches thick)
BCtk--23 to 29 inches; brown (10YR 5/3) loam, dark brown (7.5YR 4/3) moist; weak medium angular blocky structure; firm, slightly sticky and slightly plastic; few very fine roots; many fine pores; 12 percent basalt gravel; few faint clay films on faces of peds; common veins and spots of calcium carbonate; mildly alkaline (pH 7.4); abrupt wavy boundary. (5 to 10 inches thick)
Cr--29 to 34 inches; brown (10YR 5/3), olive (5Y 5/4), and reddish brown (5YR 4/4) slightly decomposed, slightly disintegrated basalt; some fractures thickly coated with calcium carbonate. (1 to 8 inches thick)
R--34 inches; basalt.
TYPE LOCATION: Gem County, Idaho; about 6 miles west of Sweet; 400 feet east and 700 feet south of the center of the northeast 1/4 of section 10, T. 7 N., R. 1 W.
RANGE IN CHARACTERISTICS:
Average annual soil temperature - 47 to 52 degrees F.
Average summer soil temperature - 65 to 69 degrees F.
Soil moisture - in the 4 to 12 inch section usually moist but is dry for 60 to 80 consecutive days in 7 out of 10 years
Depth to basalt - 20 to 40 inches
A horizons
Hue - 10YR or 7.5YR
Value - 3 through 5 dry, 2 or 3 moist
Chroma - 1 through 3 dry or moist
Organic carbon to 6 inch depth - 1.7 to 2.4 percent
Reaction - slightly acid to mildly alkaline
Bt horizons
Hue - 10YR or 7.5YR
Value - 4 through 6 dry, 3 or 4 moist
Chroma - 2 or 3 dry or moist
Texture - CL, SICL, SIC, C
Clay - 35 to 60 percent
Coarse fragments - 0 to 30 percent
Reaction - neutral to moderately alkaline
Calcium carbonate - 3 to 10 percent below depth 20 to 30 inches
Some pedons - calcium carbonate is on the bedrock and in the bedrock cracks and occasionally they are thin gravelly loam Ck horizon just above the bedrock.
COMPETING SERIES: These are the Banner, Flowell, and Gemson series. Banner, Flowell, and Gemson soils are deeper than 40 inches to bedrock. Also, Flowell soils have a weakly to strongly cemented horizon of high accumulation of lime.
GEOGRAPHIC SETTING: Gem soils are in uplands at elevations of 2,500 to 5,000 feet. Slopes range from 0 to 65 percent. The soils formed in residuum weathered from basalt or related basic igneous rock. The climate has dry summers, a frost-free season of 110 to 140 days, and a average annual precipitation of 12 to 17 inches, including 3 to 6 feet of snow. The average annual temperature is 45 to 50 degrees F.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Bakeoven, Gross, and Reywat soils and the competing Gemson soils. Bakeoven soils have bedrock within 10 inches of the surface. Gross soils have a mollic epipedon thicker than 20 inches, have a fine-loamy Bt horizon and are frigid. Reywat soils have a fine-loamy Bt horizon.
DRAINAGE AND PERMEABILITY: Well drained; slow to very rapid runoff; slow permeability.
USE AND VEGETATION: Used mainly for range; a few areas are cropped to nonirrigated small grains and alfalfa. Vegetation is chiefly bluebunch wheatgrass, Sandberg bluegrass, big sagebrush, and cheatgrass, and in places Medusahead wildrye, bitterbrush, Idaho fescue, wild buckwheat, lupine, rabbitbrush, and (or) balsamroot.
DISTRIBUTION AND EXTENT: Basalt areas of southern Idaho, eastern Oregon, and eastern Washington. The series is extensive.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Portland, Oregon
SERIES ESTABLISHED: Gem County, Idaho, 1939.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon - the zone from 0 to 15 inches (A1, A2, BA, and Bt1 horizons)
Argillic horizon - the zone from 9 to 23 inches (Bt1, Bt2, BCt horizons)
Calcic feature - the zone from 23 to 29 inches (BCtk horizon)