LOCATION CHEOSA TXEstablished Series
TAXONOMIC CLASS: Loamy-skeletal, mixed, superactive, hyperthermic, shallow Calcic Petrocalcids
TYPICAL PEDON: Cheosa very gravelly loam - rangeland. (Colors are for dry soil unless otherwise stated.)
A--0 to 3 inches; pale brown (10YR 6/3) very gravelly loam, brown (10YR 5/3) moist; moderate fine and medium subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; common very fine and fine roots; common very fine interstitial pores; few distinct discontinuous white (10YR 8/1) calcium carbonate coatings on rock fragments; 30 percent subrounded gray limestone gravel, and 10 percent subangular black chert gravel; 5.0 percent calcium carbonate equivalent; violently effervescent; moderately alkaline; clear smooth boundary. (2 to 9 inches thick).
Bk--3 to 12 inches; pale brown (10YR 6/3) extremely gravelly loam, brown (10YR 5/3) moist; weak fine and medium subangular blocky structure; slightly hard, friable, moderately sticky and moderately plastic; common very fine, fine, and medium roots; common very fine interstitial pores; very few distinct discontinuous white (10YR 8/1) calcium carbonate coatings on surfaces of peds; 45 percent subrounded gray limestone gravel, 5 percent subrounded gray limestone cobbles, and 20 percent subangular black chert gravel; coarse fragments have calcium carbonate coatings 1 to 2 mm thick; 35.0 percent calcium carbonate equivalent; violently effervescent; moderately alkaline; abrupt wavy boundary. (0 to 11 inches thick).
Bkm--12 to 24 inches; strongly cemented caliche with 1 mm thick laminar cap; common very fine roots in cracks; 60 percent subrounded gray limestone gravel, 10 percent subrounded gray limestone cobbles, and 10 percent subangular chert gravel cemented with calcium carbonate; violently effervescent; moderately alkaline; gradual smooth boundary.
Bkym--24 to 32 inches; moderately cemented caliche; common very fine roots in cracks; common fine and medium platy, slightly hard gypsum crystals around stones; 70 percent subrounded gray limestone gravel, 10 percent subrounded gray limestone cobbles, and 10 percent subangular black chert gravel; rock fragments have calcium carbonate coatings in the form of pendants from 1 to 3 mm thick on the lower sides; violently effervescent; moderately alkaline; abrupt smooth boundary.
R--32 to 80 inches; unweathered indurated conglomerate bedrock.
TYPE LOCATION: Brewster County, Texas, from the junction of U.S. Highway 90 and Texas Highway 118 in Alpine, 45.7 miles south on Texas Highway 118, 2.7 miles west-southwest on ranch road to stock pens, 1.5 miles west on ranch road, 50 feet north of road in range. (Latitude: 29 degrees, 44 minutes, 17 seconds North; Longitude: 103 degrees, 37 minutes, 58 seconds West; NAD 1927). Long Hills USGS 7.5 minute quadrangle.
RANGE IN CHARACTERISTICS:
Depth to a petrocalcic horizon: 7 to 20 inches
Depth to conglomerate bedrock: 20 to 40 inches
Rounded limestone and chert gravel above the petrocalcic horizon range from 35 to 65 percent
A surface lag of limestone and chert gravel covers 50 to 95 percent of the soil surface
Reaction: moderately alkaline
Mean annual soil temperature: 66 to 70 degrees F.
Soil moisture: Typic aridic moisture regime
A horizon
Hue: 7.5YR, 10YR
Value: 5 to 7, dry or moist
Chroma: 2 to 4, dry or moist
Texture: sandy loam, loam
Clay content: 18 to 30 percent
Silicate clay content: 12 to 25 percent
Calcium carbonate: (in the form of films, threads, and coatings on coarse fragments) none to about 5 percent by volume
Calcium carbonate equivalent: (fine earth fraction) 20 to 40 percent
Bk horizon (where present)
Hue: 7.5YR, 10YR
Value: 6 to 8, dry or moist
Chroma: 1 to 4, dry or moist
Texture: sandy loam, loam
Clay content: 18 to 28 percent
Silicate clay content: 12 to 25 percent
Calcium carbonate: (in the form of coatings on coarse fragments) 5 to 20 percent
Calcium carbonate equivalent: (fine earth fraction) 30 to 40 percent
Bkm horizon
Limestone and chert fragments occupy from 60 to 90 percent of the volume and are cemented together with calcium carbonate
Cementation: strongly cemented or indurated in the upper part and usually has a laminar cap.
The Bkym horizon, where present, texture is very gravelly or extremely gravelly sandy loam or loam. Clay content ranges from 15 to 28 percent with silicate clay content ranging from 12 to 25 percent. Gypsum content is less than 5 percent. Calcium carbonate equivalent of the fine earth fraction ranges from 30 to 50 percent.
The R horizon is indurated conglomerate bedrock. The conglomerate bedrock consists of well-rounded Cretaceous limestone gravel and subrounded Paleozoic limestone and chert gravel cemented together with calcium carbonate.
COMPETING SERIES: These are the Guvo (AZ), Hickiwan (AZ), and Ojinaga (T)(TX) series. Gurvo, Hickiwan, and Ojinaga are all in the typic aridic soil moisture regime.
GEOGRAPHIC SETTING: Cheosa soils are on gently undulating to undulating erosional uplands, usually on hillcrest landforms. Slopes range from 1 to 8 percent. The soil formed in residuum weathered from the basal Jeff Conglomerate member of the Eocene age Pruett Formation. Mean annual precipitation ranges from 10 to 13 inches, with most occurring from July to September. Mean annual air temperature is 68 to 72 degrees F. Frost-free period is 240 to 280 days. Elevation ranges from 3,000 to 4,000 feet.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Cesario, Fizzleflat, Loyplace, Mariscal, and Straddlebug series. Cesario and Fizzleflat soils are in the fine-loamy family. In addition, Cesario soils are deep to Cretaceous shale bedrock and Fizzleflat soils are moderately deep to Cretaceous shale bedrock. These soils are lower in the landscape on gently sloping uplands. Loyplace soils are lower in the landscape on footslope positions. Mariscal soils are very shallow and shallow to flaggy limestone bedrock and are on adjacent hills. Straddlebug soils are very deep, loamy soils that do not have a calcic horizon. They are on alluvial flats and floodplains and formed in zeolitic alluvium derived from tuffaceous materials.
DRAINAGE AND PERMEABILITY: Well drained. Permeability is moderate above a very slowly permeable petrocalcic horizon. Runoff is medium on slopes of 1 to 3 percent, high on slopes of 3 to 5 percent, and very high on slopes of 5 to 8 percent.
USE AND VEGETATION: This soil is used entirely for livestock grazing. Woody species present include creosotebush, catclaw, whitethorn acacia, mariola, cacti, and ocotillo. Grass species in the understory include Chino grama, black grama, bush muhly, slim tridens, perennial threeawn, tobosa, and fluffgrass. Characteristic forbs include coldenia and dogweed.
DISTRIBUTION AND EXTENT: Trans-Pecos Texas in the Southern Desertic Basins, Plains, and Mountains (MLRA 42), Desert Shrub vegetative zone. The soil is of minor extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Phoenix, Arizona
SERIES ESTABLISHED: Brewster County, Texas 1997. The name is from Cheosa Waterhole, a spring on Terlingua Creek.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - The zone from 0 to 3 inches (A horizon)
Calcic horizon - The zone from 3 to 12 inches (Bk horizon)
Petrocalcic horizon - The zone from 12 to 32 inches (Bkm and Bkym horizons).
Lithic Contact - The boundary at 32 inches (R horizon)
Superactive cation exchange activity class - CEC to percent clay ratio is 0.60 or greater. This is assumed from the abundant zeolitic minerals in the Pruett Tuff, which overlies the Jeff Conglomerate; and laboratory data from similar soils in Presidio County, Texas
Classified according to Soil Taxonomy, Second Edition, 1999; Keys to Soil Taxonomy, Tenth Edition, 2006.
Moisture and temperature regime revised for Brewster County, TX, Main Part, 2/8/08, CEM