LOCATION GEBSON CO+WYEstablished Series
TAXONOMIC CLASS: Fine-loamy, mixed, superactive Ustollic Haplocryalfs
TYPICAL PEDON: Gebson sandy loam-rangeland. (Colors are for dry soil unless otherwise stated.)
A--0 to 3 inches; brown (7.5YR 5/2) sandy loam, dark brown (7.5YR 3/2) moist; weak fine granular structure; soft, very friable, nonsticky and nonplastic; 5 percent pebbles; neutral; abrupt smooth boundary. (3 to 5 inches thick)
Bt1--3 to 7 inches; brown (7.5YR 5/2) sandy clay loam, dark brown (7.5YR 3/2) moist; weak medium subangular blocky structure; slightly hard, very friable, slightly sticky and nonplastic; common distinct clay films on ped faces; 5 percent pebbles; neutral; clear smooth boundary. (3 to 5 inches thick)
Bt2--7 to 17 inches; yellowish brown (10YR 5/4) sandy clay loam, dark yellowish brown (10YR 4/4) moist; moderate medium subangular blocky structure; slightly hard, very friable, slightly sticky and slightly plastic; common distinct clay films on ped faces; 5 percent pebbles; neutral; clear smooth boundary. (3 to 12 inches thick)
Bt3--17 to 35 inches; light yellowish brown (10YR 6/4) gravelly sandy loam, dark yellowish brown (10YR 4/4) moist; weak medium subangular blocky structure; slightly hard, very friable, nonsticky and nonplastic; few faint clay films on ped faces; 20 percent pebbles; mildly alkaline; clear wavy boundary. (0 to 20 inches thick)
Bk1--35 to 52 inches; light yellowish brown (10YR 6/4) loam, yellowish brown (10YR 5/4) moist; massive; hard, firm, slightly sticky and slightly plastic; 5 percent pebbles; strongly effervescent; many calcium carbonate concretions; moderately alkaline; gradual smooth boundary. (15 to 25 inches thick)
Bk2--52 to 60 inches; light yellowish brown (10YR 6/4) sandy clay loam, yellowish brown (10YR 5/4) moist; massive; hard, friable, slightly sticky and slightly plastic; 5 percent pebbles; strongly effervescent; few calcium carbonate concretions; moderately alkaline.
TYPE LOCATION: Park County, Colorado; 8 1/2 miles north of the town of Hartsel; 25 feet south and 100 feet east of the northwest corner of Sec. T. 11 S., R. 75 W.
RANGE IN CHARACTERISTICS: Mean annual soil temperature ranges from 37 to 46 degrees F. The thickness of the mollic epipedon ranges from 7 to 12 inches. The mollic epipedon includes the upper parts of the Bt horizon in most pedons. The depth to a consistent horizon of secondary calcium carbonates ranges from 10 to 36 inches. The depth to the base of the argillic horizon is 8 to 20 inches. Rock fragment content is 0 to 35 percent and is mainly pebbles. The moisture control section is moist in some part from April through June when the soil temperature at 20 inches is greater than 41 degrees F.
The A horizon has hue of 2.5Y through 7.5YR, value of 4 or 5 dry, 2 or 3 moist and chroma of 2 or 3. Reaction is neutral or mildly alkaline.
The Bt horizon has hue of 2.5Y through 7.5YR, value of 4 through 6 dry, 3 through 5 moist, and chroma of 3 or 4. Reaction is neutral or mildly alkaline. Btk horizons are present in some pedons and are moderately alkaline. Clay content is 18 to 35 percent silt is 15 to 35 percent, and sand content is 40 percent or more with over 30 percent being fine sand or coarser.
The Bk and C horizons have hue of 2.5Y through 7.5YR, value of 4 through 8 dry, 3 through 7 moist, and chroma of 2 through 4. Common textures are gravelly or non gravelly sandy loam and sandy clay loam, loam, and coarse sandy loam. Fine or coarser sand content is 35 percent or more. Calcium carbonate equivalent ranges from one to 14 percent.
COMPETING SERIES: These are the Amsden(WY), Buffork(WY), Cific(WY), Coldspring(CO), Croftshow(NM), Croydon, Dra(ID), Gelkie(CO), Hourglass(UT), Inchau(WY), Kezar(CO), Kittredge(CO), Leavitt(WY), Lucky(CO), Lymanson(WY), Lyonman(CA), Michelson(MT), Miracle(CO), Monad, Monida(ID), Morset(CO), Mult(UT), Newlands(CA), Oro Fino(MT), Passcreek (WY), Philipsburg(MT), Primeaux(NV), Rainbolt (WY), Rammel(ID), Shotgun(ID), Sponsor(CO), Swede(ID), Tingey(UT), Tripit(WY), Troutdale(CO), Wellsville(CO), Woosley(WY), and Youga(CO) series. The average annual precipitation in areas of Gebson soils is lower than that of all or most of the above soils. Amsden and Sponseller soils have a Bt horizon with a hue of 5YR or redder. Buffork, Cific, Inchau, Lymanson, Rainbolt, Tripit, and Troutdale soils have a paralithic contact at a depth of 20 to 40 inches. Coldsprings, Croydon, Hourglass, Kittredge, Lyonman, Monad, Newlands, Swede, and Youga soils have thicker sola and lack a horizon of secondary calcium carbonate accumulation. Dra, Kezar, Lucky, Miracle, Mult, Passcreek, Primeaux, Rammel, Shotgun, and Woosley soils have a lithic contact at a depth of 20 to 40 inches. Gelkie and Oro Fino soils have sola thicker than 20 inches; and Gelkie soils have cobbly Bt horizons, and Oro Fino soils have skeletal material below depths of 40 inches. Leavitt and Wellsville soils have less than 35 percent sand coarser than very fine in the argillic and C horizons. Michelson, Morset, and Philipsburg soils have a calcic horizon. Tingey soils have a stony Bt horizon and very stony C horizon. Croftshaw soils have less than 40 percent sand in the particle-size control section. Monida soils have a lithologic discontinuity. Sponsor soils lack consistent Bk horizons above 40 inches.
GEOGRAPHIC SETTING: Gebson soils are on fans, terraces, and rolling uplands. Slopes range from 0 to 25 percent. The soils formed in alluvium of mixed sources. The mean annual air temperature ranges from about 35 to 44 degrees F. The mean annual precipitation is 10 to 18 inches. The mean summer precipitation is about 9 inches. Elevation is 7,000 to 9,600 feet and the frost-free period is 50 to 80 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Spinney and Wellsville soils. The Spinney soils have a sandy-skeletal C horizon. The Wellsville soils have less than 35 percent fine or coarser sand in the argillic horizon.
DRAINAGE AND PERMEABILITY: Well drained; slow to very rapid runoff; moderately permeability.
USE AND VEGETATION: These soils are used for rangeland. Principal native vegetation is western wheatgrass, Arizona fescue, mountain muhly, slimstem muhly, and fringed sagebrush.
DISTRIBUTION AND EXTENT: South Park, and other mountain parks with relatively low precipitation, in Central and Northwestern Colorado. The series is of small extent.
MLRA OFFICE RESPONSIBLE: Lakewood, Colorado
SERIES ESTABLISHED: Moffat County (Moffat County Area), Colorado, 1992.
REMARKS: Last updated by the state 4/93. Diagnostic features include a mollic epipedon from 0 to 7 inches. An argillic horizon from 3 to 35 inches. This soil was proposed in Park County, Colorado, in 1984. The name is coined. The soil receives precipitation in a range peculiar to both the ustic aridic and aridic ustic regimes in Colorado, but the soil temperatures are cryic.