LOCATION TARRANT                 TX+OK

Established Series


The Tarrant series consists of soils that are very shallow and shallow to indurated limestone bedrock, interbedded with marl and chalk. These well drained soils formed in residuum derived from limestone of Cretaceous age. These nearly level to very steep soils are on summits, shoulders, and backslopes of ridges on dissected plateaus. Slopes are 1 to 50 percent. Mean annual air temperature is about 18 degrees C (66 degrees F), and the mean annual precipitation is about 533 mm (21 in).

TAXONOMIC CLASS: Clayey-skeletal, smectitic, thermic Lithic Calciustolls

TYPICAL PEDON: Tarrant cobbly clay--native pasture. (Colors are for dry soil unless otherwise stated.)

A--0 to 20 cm (0 to 8 in); very dark grayish brown (10YR 3/2) very cobbly clay, very dark brown (10YR 2/2) moist; strong very fine subangular blocky structure parting to strong medium granular; very hard, firm; common fine roots; common fine pores; carbonate masses around and on bottom of rock fragments; 35 percent limestone cobbles and 5 percent limestone gravel; violently effervescent; moderately alkaline; clear irregular boundary. (Thickness of the A horizon is 10 to 28 cm [4 to 11 in])

Ak--20 to 33 cm (8 to 13 in); brown (10YR 4/3) extremely cobbly clay, dark brown (10YR 3/3) moist; moderate very fine angular blocky structure parting to moderate medium granular; very hard, firm; common fine roots in vertical and horizontal bands; carbonate masses around and on bottom of rock fragments; 85 percent weakly cemented to strongly cemented limestone cobbles and stones; violently effervescent; moderately alkaline; abrupt wavy boundary. (Thickness of the Ak horizon is 5 to 25 cm [2 to 10 in])

R--33 to 76 cm (13 to 30 in); fractured, indurated and platy limestone bedrock and interbedded strata of weakly cemented to strongly cemented limestone about 1 to 15 cm (0.5 to 6 in) thick.

TYPE LOCATION: Menard County, Texas; From the intersection of U.S. Highway 83 and Texas Highway 29, 19.2 miles west on U.S. Highway 83, 2.6 miles east on county road, 4.9 miles north on county road, 0.5 mile northeast of county road in pastureland. (Fort McKavett NE USGS topographic quadrangle; Latitude: 30 degrees, 57 minutes, 14.8 seconds N; Longitude: 100 degrees, 3 minutes, 31.1 seconds W; NAD83)

Solum thickness: 15 to 50 cm (6 to 20 in) over limestone bedrock
Effervescence: Strongly and violently
Reaction: Slightly alkaline or moderately alkaline

Particle-size control section (weighted average):
Total clay content: 40 to 60 percent
Rock fragments: Amount-35 to 85 percent by volume

A horizon
Hue: 7.5YR or 10YR
Value: 2 to 5 dry, 2 or 3 moist
Chroma: 2 or 3 dry, 1 to 3 moist
Texture: Clay loam, silty clay or clay; and their cobbly, very cobbly, stony, or very stony phases.
Clay content: 35 to 60 percent
Rock fragments: Amount-30 to 59 percent total by volume, kind-limestone or quartziferous; Amount-0 to 15 percent, size-2 to 75 mm; amount-4 to 35 percent, size-76 to 250 mm; amount-0 to 40 percent, size-251 to 600 mm
Identifiable secondary carbonate: Amount-0 to 10 percent by volume, size-fine to medium, contrast-distinct, kind-coats and pendants, location-on bottom surfaces of and around rock fragments

Ak or Bk horizon, where present)
Hue: 7.5YR or 10YR
Value: 3 or 4, dry and moist
Chroma: 3 dry and moist
Texture: Clay; and very or extremely cobbly, stony or flaggy phases
Clay content: 40 to 60 percent
Rock fragments: Amount-35 to 85 total by volume; kind limestone and/or quartziferous; Amount-0 to 19 percent by volume, size-2 to 75 mm; Amount-10 to 50 percent, size-76 to 250 mm, Amount-0 to 60 percent, size-76 to 250 mm, location- extremely cobbly, stony, and flaggy phases when present are typically immediately above the bedrock
Identifiable secondary carbonates: Amount-0 to 10 percent by volume, size-fine to medium, contrast-distinct, kind-coats and pendants, location-on bottom surfaces of and around rock fragments

R layer
Cementation: Strongly cemented or indurated with weakly to moderately cemented interbeds
Identifiable calcium carbonates: kind-cemented primary and secondary calcium carbonates, location-in fractures and on rock fragments

COMPETING SERIES: There are no competing series currently in the same family. Similar soils are Aledo (TX), Altuda (TX), Eckrant (TX), Ector (TX), Oplin (TX), Prade (TX), and Purves (TX).
Aledo, Altuda, Ector and Oplin soils: Have less than 35 percent clay in the fine-earth fraction and have carbonatic mineralogy.
Eckrant soils: Do not have a calcic horizon.
Prade soils: Have a petrocalcic horizon.
Purves soils: Have less than 35 percent coarse fragments in the control section.

Parent material: Residuum derived from limestone of Lower Cretaceous age, including interbedded chalk and marl.
Landscape: Dissected plateaus
Landform: Summits, shoulders, and backslopes of ridges
Slope: 1 to 50 percent, but is commonly 1 to 8 percent
Climate: Dry subhumid
Soil moisture: Typic ustic soil moisture regime. The soil moisture control section is dry in some or all parts for more than 90 but less than 150 cumulative days in normal years. June through August and December through February are the driest months. These soils are intermittently moist in September through November and March through May.
Precipitation Pattern: The majority of the yearly amount occurs during the fall and spring months. The winter and summer months are normally drier.
Mean annual air temperature: 17 to 21 degrees C (62 to 70 degrees F)
Mean annual precipitation: 508 to 864 mm (20 to 34 in)
Frost free period: 230 to 260 days
Elevation: 305 to 746 m (1,000 to 2,450 ft)
Thornthwaite annual P-E indices: 30 to 44

GEOGRAPHICALLY ASSOCIATED SOILS: These are Brackett (TX), Campwood (TX), Eckrant (TX), Kavett (TX), and Valera (TX) series.
Brackett soils: Occur on backslope positions.
Campwood soils: Are very deep alluvial soils on stream terraces.
Eckrant, Kavett, and Real soils: Occur on similar landform positions.

DRAINAGE AND PERMEABILITY: Well drained. Permeability is moderately slow. Runoff is negligible on 0 to 1 percent slopes, very low on 1 to 3 percent slopes, low on 3 to 5 percent slopes, medium on 5 to 12 percent slopes, high on 12 to 20 percent slopes and very high on 20 to 50 percent slopes.

USE AND VEGETATION: Mainly rangeland and wildlife habitat. The climax plant community is a tall grass savannah with motts of live oak throughout the landscape. The dominant grasses are little bluestem and sideoats grama. Other grasses include yellow Indiangrass, fall witchgrass, wildrye, green sprangletop, meadow dropseed, cane and pinhole bluestem, hairy grama, Texas wintergrass, curly mesquite and buffalograss. Woody plants include live oak, shin oak, evergreen sumac, hackberry, elbowbush, redbud, and white honeysuckle. Forbs, such as orange zexmenia, Engelmann daisy, bundleflower, snout bean, and bushsunflower, are present. With continued over grazing, the site could potentially deteriorate to a plant population sideoats grama, buffalograss, hairy grama, dropseeds, and the woody plants. If this destructive grazing practice continues, the site will deteriorate to a plant population of Ashe juniper, Texas persimmon, live oak, Texas grama, hairy tridens, curly mesquite, threeawns, prairie coneflower, and broomweed.

DISTRIBUTION AND EXTENT: West-Central Texas and Oklahoma. Central Great Plains Winter Wheat and Range Region, LRR-H: MLRA 78A-Rolling Limestone Prairie; MLRA 78B-Central Rolling Red Plains, Western Part; and MLRA 80B-Texas North-Central Prairies. Southwest Plateaus and Plains Range and Cotton Region, LLR-I: MLRA 81A-Edwards Plateau, Western Part; MLRA 81B-Edwards Plateau, Central Part; MLRA 81C-Edwards Plateau, Eastern Part. Southwestern Prairies Cotton and Forage Region, LLR-J: MLRA 85-Grand Prairie. This series is extensive with about 3,400,000 acres.


SERIES ESTABLISHED: McLennan County, Texas; 1947.

REMARKS: The province of occurrence for the Tarrant series was redefined in 1997. Tarrant soils are now limited to the Edwards Plateau materials with a P-E index of 30 to 44.
The calcic horizon in the typical pedon is questionable and this series needs to be studied over its full extent and a new typical pedon selected.

Diagnostic horizons and features recognized in this pedon are:
Particle-size control section: 0 to 33 cm (0 to 13 in)
Mollic epipedon: 0 to 33 cm (0 to 13 in) (A and Ak horizons)
Calcic horizon: 20 to 33 cm (8 to 13 in) (Ak horizon and the upper few inches of limestone bedrock plugged with secondary carbonates.)
Lithic contact: 33 cm (13 in) (top of R layer)

ADDITIONAL DATA: Reference samples from Menard County, TX327, Texas, sampled by SSL, Lincoln, NE, 10/64, include 40A4524, 40A4525, 40A4526, and 40A4527. Sample 40A4527 is the OSD type location.

TAXONOMIC VERSION: Keys to Soil Taxonomy, 11th Edition, 2010.

National Cooperative Soil Survey