LOCATION PARDO                   TX

Established Series
Rev. LEL/JLR/ACT
10/2012

PARDO SERIES

The Pardo series consists of soils that are very shallow and shallow to a petrocalcic horizon and hard bedrock. They are well drained, moderately permeable soils that formed in residuum derived from Mitchell Mesa Ignimbrite (welded tuff). These soils are on gently undulating to undulating summits and crests of bedrock-capped mesas. Slopes range from 1 to 8 percent.

TAXONOMIC CLASS: Loamy-skeletal, mixed, superactive, thermic Lithic Petrocalcic Calciustolls

TYPICAL PEDON: Pardo gravelly clay loam - rangeland. (Colors are for dry soil unless otherwise stated.)

A--0 to 5 inches; very dark grayish brown (10YR 3/2) gravelly clay loam, very dark brown (10YR 2/2) moist; moderate medium and coarse subangular blocky parting to moderate fine and medium granular structure; hard, firm, moderately sticky and moderately plastic; 20 percent subangular ignimbrite gravel; few distinct discontinuous white (10YR 8/1) calcium carbonate coatings on rock fragments; slightly effervescent; moderately alkaline; clear smooth boundary. (4 to 8 inches thick)

Bk1--5 to 11 inches; dark grayish brown (10YR 4/2) very cobbly clay loam, very dark grayish brown (10YR 3/2) moist; moderate fine and medium subangular blocky parting to moderate fine and medium granular structure; hard, firm, moderately sticky and moderately plastic; 25 percent subangular ignimbrite gravel, and 20 percent subangular ignimbrite cobbles; many prominent continuous white (10YR 8/1) calcium carbonate coatings on rock fragments; violently effervescent; moderately alkaline; clear smooth boundary.

Bk2--11 to 15 inches; grayish brown (10YR 5/2) very gravelly loam, dark grayish brown (10YR 4/2) moist; weak fine and medium subangular blocky structure; slightly hard, friable, moderately sticky, and slightly plastic; 10 percent subangular ignimbrite gravel, 30 percent subangular detached caliche gravel, and 15 percent subangular detached caliche cobbles; many prominent continuous white (10YR 8/1) calcium carbonate coatings on rock fragments; violently effervescent; moderately alkaline; abrupt smooth boundary. (combined thickness of Bk horizons is 6 to 12 inches)

Bkkm--15 to 18 inches; strongly cemented petrocalcic, violently effervescent; abrupt smooth boundary. (1 to 4 inches thick)

R--18 to 80 inches; unweathered, indurated ignimbrite bedrock, moist; noneffervescent

TYPE LOCATION: Brewster County, Texas; from the junction of U.S. Highway 90 and Texas Highway 118 in Alpine, 12 miles west on U.S. Highway 90 to ranch road, 7.25 miles east-southeast on ranch road past 101 Ranch headquarters to cattle guard, 2.7 miles south-southwest on ranch road to well, 3.1 miles south and south-southeast on ranch road to old Crossen Ranch headquarters, 0.25 mile east on ranch road, 2 miles southeast on ranch road to water storage tank on OT mesa, 100 feet southeast and 50 feet northeast in rangeland; Goat Mountain USGS 7.5 minute quadrangle.
Latitude: 30 degrees, 3 minutes, 32 seconds North; Longitude: 103 degrees, 44 minutes, 44 seconds West; NAD 1927.

RANGE IN CHARACTERISTICS:

Soil moisture: Aridic ustic moisture regime

Depth to a petrocalcic horizon: 6 to 18 inches

Depth to lithic contact: 8 to 20 inches

Clay content: 20 to 35 percent

Ignimbrite and detached caliche rock fragments: 35 to 80 percent

A horizon
Hue: 7.5YR, 10YR
Value: 2 to 5, dry or moist
Chroma: 2 to 3, dry or moist
Texture: commonly loam, but ranges to clay loam
Ignimbrite and detached caliche rock fragments: 15 to 35 percent
Calcium carbonate equivalent: 2 to 15 percent

Bk horizons
Hue: 7.5YR, 10YR
Value: 3 to 6 dry, 3 to 5 moist
Chroma: 2 to 4, dry or moist
Texture: loam, clay loam
Ignimbrite and detached caliche rock fragments: 35 to 80 percent
Calcium carbonate equivalent: 20 to 40 percent

Bkm horizon
It is strongly cemented or indurated caliche
Most pedons have an indurated laminar cap 2 to 5 mm thick

R layer
It is noncalcareous, unweathered, indurated Ignimbrite bedrock

COMPETING SERIES: This is the Noelke (TX) series. Noelke soils are underlain by limestone bedrock, do not have coarse fragments of ignimbrite in the control section, and are moist in the soil moisture control section during May and June and occur on the Edwards Plateau.

GEOGRAPHIC SETTING: Pardo soils are on bedrock-capped mesas. Slopes range from 1 to 8 percent. These soils formed in residuum weathered from Mitchell Mesa Ignimbrite (welded tuff). Mean annual precipitation ranges from 14 to 20 inches, with most occurring from July through September. Mean annual air temperature ranges from 57 to 70 degrees F. Frost-free period ranges from 180 to 240, and elevation ranges from 4,000 to 6,995 feet.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Boracho, Brewster, Espy, and Volco series. Boracho and Espy soils are more than 40 inches deep to bedrock. Brewster and Volco soils do not have a petrocalcic horizon above the bedrock. Brewster soils are on adjacent hills and mountains. Volco soils are on similar bedrock-capped mesas.

DRAINAGE AND PERMEABILITY: Well drained. Permeability is moderate in the surface layer, and slow or very slow in the petrocalcic horizon and ignimbrite bedrock. Runoff is low on 1 to 5 percent slopes, medium on 5 to 8 percent slopes.

USE AND VEGETATION: This soil is used for livestock grazing and wildlife habitat. Woody species consist of redberry juniper, allthorn, prickly pear, agarita, lotebush, and sachuista. Grasses include blue grama, sideoats grama, threeawn, wolftail, black grama, fluffgrass, silver bluestem, and hairy grama.

DISTRIBUTION AND EXTENT: West Texas. MLRA 42. The soil is moderately extensive.

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

SERIES ESTABLISHED: Brewster County, Texas, 1997. The name is taken from a mesa in western Presidio County where the series was first described.

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

Mollic epipedon - the zone from 0 to 11 inches (A and Bk1 horizons)

Calcic horizon - the zone from 5 to 15 inches (Bk horizons)

Petrocalcic horizon - the zone from 15 to 18 inches (Bkm horizon)

Lithic contact - the boundary at 18 inches (R layer)

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 Mitchell Mesa Ignimbrite, and laboratory data from similar soils in Presidio County.

Classified according to Soil Taxonomy, Second Edition, 1999; Keys to Soil Taxonomy, Eleventh Edition, 2010

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

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

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National Cooperative Soil Survey
U.S.A.