LOCATION GEMELO                  TX

Established Series
LEL/JLR/ACT
10/2012

GEMELO SERIES

The Gemelo series consists of very deep, well drained, moderately permeable soils on fan aprons. These soils formed in gravelly alluvium derived mainly from tuff of the Duff and Pruett Formations. Slopes range from 1 to 3 percent.

TAXONOMIC CLASS: Coarse-loamy, mixed, superactive, thermic Sodic Ustic Haplocambids

TYPICAL PEDON: Gemelo gravelly fine sandy loam--rangeland (Colors are for dry soil unless otherwise stated.)

A--0 to 6 inches; brown (10YR 5/3) gravelly fine sandy loam, brown (10YR 4/3) moist; weak medium and coarse subangular blocky structure; thin platy structure in the upper 2 inches; soft, very friable, slightly sticky and slightly plastic; many fine and medium roots; few fine tubular pores; 20 percent subangular tuff gravel; 2 percent calcium carbonate equivalent; strongly effervescent; moderately alkaline; clear smooth boundary. (4 to 9 inches thick)

Bn--6 to 14 inches; brown (10YR 5/3) fine sandy loam, brown (10YR 4/3) moist; moderate medium and coarse subangular blocky structure parting to moderate fine and medium subangular blocky; slightly hard, friable, slightly sticky and slightly plastic; common fine and medium roots; few fine tubular pores; 1 percent subangular tuff gravel; 4 percent calcium carbonate equivalent; violently effervescent; moderately alkaline; clear smooth boundary. (7 to 19 inches thick)

Bkn1--14 to 25 inches; pale brown (10YR 6/3) very gravelly fine sandy loam, brown (10YR 5/3) moist; weak medium and coarse subangular blocky structure; soft, very friable, slightly sticky and slightly plastic; few very fine and fine roots; many distinct continuous white (10YR 8/1) calcium carbonate coatings on rock fragments and very few distinct discontinuous white (10YR 8/1) calcium carbonate coatings on surfaces of peds; few fine irregular white (10YR 8/1) masses of calcium carbonate between peds; 55 percent subangular tuff gravel; 4 percent calcium carbonate equivalent; violently effervescent; moderately alkaline; gradual smooth boundary. (11 to 34 inches thick)

Bkn2--25 to 36 inches; pale brown (10YR 6/3) fine sandy loam, brown (10YR 5/3) moist; weak medium and coarse subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; few very fine and fine roots; few distinct discontinuous white (10YR 8/1) calcium carbonate coatings on rock fragments; 1 percent subangular tuff gravel; 3 percent calcium carbonate equivalent; violently effervescent; moderately alkaline; gradual smooth boundary. (0 to 15 inches thick)

Bkn3--36 to 54 inches; pale brown (10YR 6/3) very gravelly fine sandy loam, brown (10YR 5/3) moist; weak medium and coarse subangular blocky structure; soft, very friable, slightly sticky and slightly plastic; many distinct continuous white (10YR 8/1) calcium carbonate coatings on rock fragments, and very few distinct discontinuous white (10YR 8/1) calcium carbonate coatings on surfaces of peds; few fine irregular white (10YR 8/1) masses of calcium carbonate between peds; 45 percent subangular tuff gravel; 4 percent calcium carbonate equivalent; violently effervescent; moderately alkaline; clear smooth boundary. (0 to 20 inches thick)

BCkn--54 to 80 inches; light brownish gray (10YR 6/2) gravelly sandy loam, dark grayish brown (10YR 4/2) moist; weak medium and coarse subangular blocky structure; alternating strata of sandy loam and gravel; slightly hard, friable, slightly sticky and slightly plastic; common distinct discontinuous white (10YR 8/1) calcium carbonate coatings on rock fragments; 30 percent subangular tuff gravel; 2 percent calcium carbonate equivalent; strongly effervescent; moderately alkaline. (0 to 26 inches thick)

TYPE LOCATION: Brewster County, Texas; from the junction of U.S. Highway 90 and Texas Highway 118 in Alpine; 32.3 miles south on Texas Highway 118 to main 02 Ranch headquarters gate, 2.55 miles southwest on main 02 Ranch headquarters road to Whirlwind Spring Corral, 1.90 miles northwest to junction, 2.75 miles west on ranch road to junction, 2.65 miles west on ranch road to junction, 0.25 mile southeast to old Duff Ranch Headquarters, 2.10 miles north to drill hole, 400 feet east of drill hole in range. Duff Springs USGS 7.5 minute topographic quadrangle. Latitude: 29 degrees, 58 minutes, 24 seconds North: Longitude: 103 degrees, 42 minutes, 39 seconds West. NAD 1927.

RANGE IN CHARACTERISTICS:
Soil Moisture: Ustic aridic soil moisture regime. The soil moisture control section is usually dry in all parts less than three-fourths of the time that the soil temperature exceeds 41 degrees F.

Particle-size control section (weighted average)
Clay content: 14 to 18 percent
Rock fragments: less than 35 percent

Reaction: slightly alkaline to moderately alkaline

Calcium carbonate equivalent: 1 to 4 percent

Organic carbon: decrease irregularly with increasing depth between 10 and 50 inches at the surface

Sodium absorption ratio: 13 to 35 percent within 40 inches of surface.

A horizon
Hue: 7.5YR, 10YR
Value: 4 through 6, dry or moist
Chroma: 2 through 4, dry or moist
Texture: fine sandy loam, loam
Rock fragments: 15 to 25 percent

Bn horizons
Hue: 7.5YR, 10YR
Value: 4 through 7, dry or moist
Chroma: 2 through 4, dry or moist
Texture: sandy loam, fine sandy loam, very fine sandy loam, loam
Stratified with thin layers of material that contain 0 to 20 percent gravel

Bkn horizons
Hue: 7.5YR, 10YR
Value: 5 through 7, dry or moist
Chroma: 2 through 4, dry or moist
Texture: sandy loam, fine sandy loam, loam
Stratified with layer of non-gravelly material
Rock fragments: 1 to 60 percent

BCkn and C horizons
Hue: 7.5YR, 10YR
Value: 6 or 7, dry or moist
Chroma: 2 through 4, dry or moist
Texture: fine sand, sandy loam, fine sandy loam
Rock fragments: 20 to 35 percent

COMPETING SERIES: There are no competing series.

GEOGRAPHIC SETTING: Gemelo soils are on fan aprons at the base of scarps. These soils formed in gravelly alluvium derived mainly from tuff of the Duff and Pruett Formations. Mean annual precipitation ranges from 10 to 15 inches, with most occurring during July through September. Mean annual air temperature ranges from 62 to 68 degrees F. Frost-free period is 210 to 260 days. Elevation ranges from 3,500 to 5,000 feet.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Reduff, Scotal, and Straddlebug soils. Reduff and Scotal soils are in the loamy-skeletal family, and are shallow to tuffaceous bedrock. These soils are on erosional hills and mountains in higher landscapes. Straddlebug soils are in the fine-loamy family, and are on alluvial fan remnants lower in the landscape.

DRAINAGE AND PERMEABILITY: Gemelo soils are well drained. Permeability is moderately rapid. Runoff is negligible on slopes of less than 1 percent and very low on 1 to 3 percent. These soils receive fast-moving overland water flow originating from adjacent hills, mountains, and scarps.

USE AND VEGETATION: This soil is used for livestock grazing and wildlife habitat. Native vegetation is a desert grassland with scattered creosotebush, mesquite, tarbush, mariola, cacti, and broom snakeweed. Native grasses include fluffgrass, bush muhly, black grama, blue grama, perennial threeawn, burrograss, and tobosagrass, with scattered alkali sacaton along small channels.

DISTRIBUTION AND EXTENT: West Texas. MLRA 42. Desert Grassland Vegetative Zone. The soil is of moderate extent.

MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Phoenix, Arizona

SERIES ESTABLISHED: Brewster County, Texas, 1997. The name is from a mesa west of the type location.

REMARKS: Diagnostic horizons and features recognized in this pedon are:

Ochric epipedon - the zone from 0 to 6 inches (A horizon)

Cambic horizon - the zone from 6 to 80 inches (Bn, Bkn, B'n, B'kn, and BCkn horizons)

Sodic feature - SAR from 13 to 35 percent within 40 inches of the surface

Ustic feature - the soil has an aridic moisture regime that borders the ustic moisture regime

Fluventic feature - These soils are assumed to have an irregular decrease in organic carbon content based on stratification from a depth of 10 to 50 inches. Similar soils in similar geomorphic position have an irregular decrease in organic carbon

Classified according to Soil Taxonomy, Second Edition, 1999; Keys to Soil Taxonomy, Tenth Edition, 2006.

Update and revisions for Recorrelation of Brewster County, TX, Main Part, 2/12/08, CEM

Revised for the correlation of Presidio County, Texas ; Oct, 2012, WWJ

ADDITIONAL DATA: Classification change from Ustifluventic Haplocambids to Sodic Ustic Haplocambids based on NSSL data (S95TX-043-005).

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National Cooperative Soil Survey
U.S.A.