Established Series


The Georgetown series consists of moderately deep, well drained, very slowly permeable soils that have formed over indurated limestone of Cretaceous age. These soils occur on nearly level to very gently sloping dissected plateaus. Slope ranges from 0 to 3 percent. Mean annual air temperature is about 19 degrees C (66 degrees F), and mean annual precipitation is about 864 mm (34 in).

TAXONOMIC CLASS: Very-fine, mixed, active, thermic Udic Paleustolls

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

A--0 to 18 cm (0 to 7 in); brown (7.5YR 4/2) clay loam, dark brown (7.5YR 3/2) moist; moderate fine subangular blocky and granular structure; hard, firm; few fine roots; few fragments of chert; slightly acid; clear smooth boundary. Thickness is 13 to 28 cm (5 to 11 in)

Bt1--18 to 46 cm (7 to 18 in); reddish brown (5YR 4/3) clay, dark reddish brown (5YR 3/3) moist; moderate fine angular blocky structure; very hard, very firm; few fine roots; few fine pores; clay films on faces of peds; few fragments of chert; neutral; abrupt wavy boundary. Thickness is 13 to 23 cm (5 to 9 in)

Bt2--46 to 89 cm (18 to 35 in); reddish brown (5YR 5/4) cobbly clay, reddish brown (5YR 4/4) moist; moderate fine and very fine angular blocky structure; very hard, firm; common fine roots; clay films on peds; 25 percent limestone and chert fragments from 1/4 inch to 4 inches in diameter; slightly acid; abrupt wavy boundary. Thickness is 25 to 53 cm (10 to 21 in)

R--89 to 119 cm (35 to 47 in); fractured indurated limestone bedrock with brown or pink silty clay loam in interstices and crevices.

TYPE LOCATION: Williamson County, Texas; one mile south/southwest of Williamson County Courthouse in rangeland (1000 feet west of the West Side Intermediate School in Georgetown)
USGS topographic quadrangle: Round Rock, Texas;
Latitude: 30 degrees, 37 minutes, 25.39 seconds N;
Longitude: 97 degrees, 41 minutes, 16.97 seconds W;
Datum: WGS84

Soil moisture: Udic ustic moisture regime
Depth to limestone bedrock: 51 to 102 cm (20 to 40 in)
Mollic epipedon: 20 to 51 cm (8 to 20 in) thick
Surface Fragments: 2 to 30 percent by area total, mostly chert gravel, 0 to 3 percent limestone cobbles, flagstones, and/or stones

Particle-size control section (weighted average)
Clay content: 60 to 80 percent

A horizon
Hue: 5YR to 10YR
Value: 2 to 4
Chroma: 2 or 3
Texture: loam, clay loam or their stony counterparts
Clay content: 20 to 40 percent
Fragments: 5 to 20 percent by volume total; 5 to 15 percent, mostly chert gravel; 0 to 5 percent, limestone cobbles and stones
Structure: grade-moderate to strong, size-very fine to fine, type-granular and subangular blocky
Reaction (pH): slightly acid to neutral (6.1-7.3)

Bt horizon
Hue: 2.5YR to 7.5YR
Value: 3 to 8
Chroma: 3 to 8
Texture: clay, stony clay, cobbly clay or gravelly clay
Clay content: 60 to 80 percent
Fragments: 2 to 35 percent by volume total; 2 to 30 percent, chert gravel; 0 to 10 percent, limestone cobbles and stones
Identifiable secondary carbonate: masses or very weakly to strongly cemented concretions of calcium carbonate occur in some pedons below depths of 71 cm (28 in)Reaction (pH): slightly acid to slightly alkaline (6.1-7.8)

R layer
Indurated or strongly cemented limestone that is interbedded with limy earth in some pedons

COMPETING SERIES: There are no competing series in the same family. Similar soils are the Bexar, Hensley, Lindy, Rumple, Speck, Tarpley, and Topia series.
Bexar soils: have Bt horizons with less than 60 percent clay in the particle-size control section
Hensley and Lindy soils: do not have mollic epipedons
Rumple soils: have more than 35 percent coarse fragments and less than 60 percent clay in the particle-size control section
Speck and Tarpley soils: are less than 51 cm (20 in) deep to bedrock
Topia soils: have vertic properties with prominent cracks and occur in a slightly drier climate

Parent material: The soil formed in reddish clay loams and clays over indurated limestone and limestone interbedded with limy earth of the Edwards formation of the Cretaceous system.
Landscape: dissected plateaus
Landform: summits and shoulders of broad ridges
Slopes: 0 to 3 percent
Precipitation pattern: The majority of the yearly rainfall amount occurs during the fall and spring months with the winter and summer months typically being drier.
Mean annual precipitation: 813 to 914 mm (32 to 36 in)
Thornthwaite annual P-E index: 44 to 54
Mean annual air temperature: 18.3 to 20.0 degrees C (65 to 68 degrees F)
Frost-free period: 230 to 260 days
Elevation: 182.9 to 381.0 m (600 to 1,250 ft)

GEOGRAPHICALLY ASSOCIATED SOILS: These include the Anhalt, Eckrant, and Tarpley series. These soils occur on similar surfaces.
Anhalt soils: have vertic properties and do not have argillic horizons
Eckrant soils: are less than 51 cm (20 in) deep to bedrock and have more than 35 percent coarse fragments in the particle-size control section
Tarpley soils: are less than 51 cm (20 in) deep to bedrock

DRAINAGE AND PERMEABILITY: Well drained. Runoff is very high. Permeability is very slow.

USE AND VEGETATION: Used mainly for rangeland. Some areas are used for small grain and grain sorghums. Native vegetation consists of little bluestem, big bluestem, indiangrass, Texas needlegrass, sideoats grama, tall dropseed, silver bluestem, Texas cupgrass, live oak, and post oak.

DISTRIBUTION AND EXTENT: Central Texas; mostly in the limestone areas of the Edwards Plateau and Grand Prairie. The series is of moderate extent.


SERIES ESTABLISHED: Williamson County, Texas; 1981.

REMARKS: These soils were formerly included in the Speck and Bexar series.

Edited 01/2016 (RFG-JRJ): Changed classification from Argiustolls to Paleustolls based on abrupt textural change. Changed to tabular format. Added metric measurements. Updated competing series, geographic setting, and associated soils sections.

Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon - 0 to 46 cm (0 to 18 in) (A and Bt1 horizons)
Argillic horizon - 18 to 89 cm (7 to 35 in) (Bt horizons)
Lithic contact - 89 cm (35 in)
Pale feature - an abrupt textural change at 18 cm (7 in) between the A and Bt1 horizons

ADDITIONAL DATA: Engineering test data for pedons S74TX491025, S77TX491013

Taxonomic Version: Keys to Soil Taxonomy, Twelfth Edition, 2014

National Cooperative Soil Survey