LOCATION TARRANT                 TX

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 18.3 degrees C (65 degrees F), and the mean annual precipitation is about 635 mm (25 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 silty clay, very dark brown (10YR 2/2) moist; strong very fine subangular blocky structure parting to strong medium granular; very hard, firm; moderately sticky, moderately plastic; many fine and medium roots; common fine pores; carbonate masses around and on bottom of rock fragments; 35 percent limestone cobbles and 5 percent limestone gravel; strongly effervescent; moderately alkaline; clear irregular boundary. (Thickness 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; moderately sticky, moderately plastic; common fine and medium 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 that are more or less oriented but not continuous and a few are slightly tilted from horizontal plane; cracks between limestone fragments are up to 2 inches wide vertically and about 1 inch wide horizontally; violently effervescent; moderately alkaline; abrupt wavy boundary. (Thickness 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 Ranch Road 2291 in Menard, 1.2 miles south on U.S. Highway 83, 150 feet W of edge of US Highway 83 in native pastureland.
USGS topographic quadrangle: Menard, Texas;
Latitude: 30 degrees, 53 minutes, 32.9 seconds N;
Longitude: 99 degrees, 46 minutes, 41.0 seconds W;
Datum: WGS84

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.
Depth to Lithic bedrock: 15 to 50 cm (6 to 20 in)
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: 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: 20 to 59 percent total by volume, limestone or quartziferous; 5 to 25 percent, 2 to 75 mm; 15 to 35 percent, 75 to 250 mm; 0 to 20 percent, 250 to 600 mm
Identifiable secondary carbonate: 0 to 10 percent by volume, fine to medium, distinct, coats and pendants, 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, silty clay; and very or extremely cobbly, stony or flaggy phases
Clay content: 40 to 60 percent
Rock fragments: 35 to 85 total by volume; limestone and/or quartziferous; 5 to 19 percent by volume, 2 to 75 mm; 30 to 50 percent, 75 to 250 mm, 0 to 50 percent, 250 to 600 mm; extremely cobbly, stony, and flaggy phases when present are typically immediately above the bedrock
Identifiable secondary carbonates: 0 to 10 percent by volume, fine to medium, distinct, coats and pendants, on bottom surfaces of and around rock fragments

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

COMPETING SERIES: There are no series currently in the same family. Similar soils are Aledo, Altuda, Eckrant, Ector, Oplin, Prade, and Purves.
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 and paralithic bedrock.
Purves soils: Have less than 35 percent coarse fragments in the particle-size 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 hills and ridges
Slope: 1 to 50 percent, but is commonly 1 to 8 percent
Precipitation Pattern: The majority of the yearly rainfall occurs during the fall and spring months. These soils are intermittently moist in September through November and March through May. June through August and December through February are the driest months.
Mean annual precipitation: 508 to 813 mm (20 to 32 in)
Thornthwaite annual P-E indices: 30 to 44
Mean annual air temperature: 16.7 to 21.1 degrees C (62 to 70 degrees F)
Frost free period: 210 to 260 days
Elevation: 304.8 to 823.0 m (1,000 to 2,700 ft)

GEOGRAPHICALLY ASSOCIATED SOILS: These are Brackett, Campwood, Eckrant, Kavett, and Valera series.
Brackett soils: Have paralithic bedrock, less than 35 percent coarse fragments, and occur on backslope positions.
Campwood soils: Are very deep alluvial soils on stream terraces.
Eckrant soils: Occur on similar landform positions.
Kavett soils: Have a petrocalcic horizon, less than 35 percent coarse fragments in the particle-size control section, and occur on similar landform positions.
Real soils: Have paralithic bedrock, less than 35 percent clay content in the particle-size control section, and occur on similar landform positions.

DRAINAGE AND PERMEABILITY: Well drained. Permeability is moderately slow. Runoff is low on 0 to 1 percent slopes, medium on 1 to 5 percent slopes, high on 5 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. Central Great Plains Winter Wheat and Range Region, LRR-H: MLRA 78A-Rolling Limestone Prairie 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.

Edited 10/2016 (RFG-THW): Updated competing series, geographic setting, and associated soils sections.

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)
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 Lab pedon numbers 40A4526 and 40A4527. Sample 40A4527 is the OSD type location.

Taxonomic Version: Keys to Soil Taxonomy, 12th Edition, 2014.

National Cooperative Soil Survey