LOCATION POINT ISABEL       TX

POINT ISABEL SERIES

TAXONOMIC CLASS: Fine, mixed, active, hyperthermic Typic Calciustepts

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

A1--0 to 20 cm (0 to 8 in); light brownish gray (10YR 6/2) clay loam, dark grayish brown (10YR 4/2) moist; weak, fine granular and subangular blocky structure; slightly hard, friable; strongly effervescent; moderately alkaline; clear smooth boundary.

A2--20 to 30 cm (8 to 12 in); dark grayish brown (10YR 4/2) clay, very dark grayish brown (10YR 3/2) moist; moderate fine subangular blocky structure; hard, firm; strongly effervescent; moderately alkaline; clear wavy boundary. (Combined thickness of the A horizons is 10 to 41 cm [4 to 16 in].)

Bkn1--30 to 48 cm (12 to 19 in); light brownish gray (10YR 6/2) clay, grayish brown (10YR 5/2) moist; moderate coarse prismatic structure parting to moderate fine and medium angular blocky; hard, firm; common films and threads of calcium carbonate; strongly effervescent; moderately alkaline, abrupt wavy boundary.

Bkn2--48 to 56 cm (19 to 22 in); grayish brown (10YR 5/2) clay loam, very dark grayish brown (10YR 3/2) moist; moderate coarse prismatic structure parting to moderate fine angular blocky; hard, firm; common films and threads of calcium carbonate; strongly effervescent; moderately alkaline; abrupt wavy boundary.

Bkn3--56 to 94 cm (22 to 37 in); light brownish gray (10YR 6/2) clay, grayish brown (10YR 5/2) moist; moderate fine and medium angular blocky structure; hard, firm; few films and threads of calcium carbonate; strongly effervescent; moderately alkaline; abrupt wavy boundary. (Combined thickness of the Bk horizons is 76 to 152 cm [30 to 60 in].)

Bknb1--94 to 107 cm (37 to 42 in); gray (10YR 5/1) clay, very dark grayish brown (10YR 3/2) moist; moderate fine subangular blocky structure; hard, firm; few threads of calcium carbonate; strongly effervescent; moderately alkaline; clear wavy boundary. (Combined thickness of the Bkb horizons is 76 to 114 cm [30 to 45 in].)

Bknb2--107 to 203 cm (42 to 65 in); light gray (10YR 7/2) clay, grayish brown (10YR 5/2) moist; moderate fine and medium angular blocky structure; hard, firm; common threads and films of calcium carbonate; strongly effervescent; moderately alkaline.

TYPE LOCATION: Cameron County, Texas; from the intersection of Texas Highway 4 and Farm Road 511, which is about 0.5 mile northeast of Brownsville International Airport; 7.6 miles east on Texas Highway 4; 0.2 mile north on field road; 250 feet west in rangeland.

RANGE IN CHARACTERISTICS:
Soil Moisture: An ustic soil moisture regime.
Depth to secondary calcium carbonate: 10 to 41 cm (4 to 16 in)
Depth to calcic horizon: 10 to 41 cm (4 to 16 in)
Depth to buried A and B horizons: 46 to 127 cm (18 to 50 in)

A horizon
Hue: 10YR
Value: 4 to 6
Chroma: 2 or 3
Texture: clay loam or silty clay loam
EC (dS/m): 1 to 20
SAR: 11 to 62
Effervescence: slightly to strongly
Reaction: moderately alkaline to strongly alkaline

Bk horizon
Hue: 10YR
Value: 5 or 6
Chroma: 2
Texture: silty clay loam, clay loam or clay
Clay content: 35 to 55
Identifiable secondary carbonate: 2 to 10 percent, fine and medium, films, threads, and filaments in matrix
Identifiable salts: 2 to 7 percent, fine masses, in matrix
EC (dS/m): 4 to 40
SAR: 72 to 95
Effervescence: slight to violent
Reaction: moderately alkaline to strongly alkaline

COMPETING SERIES: There are no other series in the same family. Similar soils include the Copita, Garceno, Lalinda, Latina, Maverick, and Sejita series.
Copita and Lalinda soils: have less than 35 percent clay in the particle-size control section.
Garceno and Maverick soils: are dry in the moisture control section for longer periods and, in addition, Maverick soils have sola less than 100 cm (40 in) in thickness.
Latina and Sejita soils: have a salic horizon and have seasonal water tables within 76 cm (30 in) of the surface.

GEOGRAPHIC SETTING:
Parent Material: calcareous loamy and clayey eolian deposits of Holocene age
Landform: backside of strandplains (few areas in swales of strandplains)
Slope: 1 to 15 percent
Mean annual temperature: 22 to 24 degrees C (72 to 75 degrees F)
Mean annual precipitation: 635 to 752 mm (25 to 30 in)
Frost-free period: 300 to 350 days
Elevation: 2 to 9 m (6.6 to 29.5 ft)
Thornthwaite annual P-E indices: 31 to 44

GEOGRAPHICALLY ASSOCIATED SOILS: These include the competing Sejita series and the Barrada and Lomalta series.
Barrada soils: are on linear plains and saturated for periods of 4 to 6 months during most years.
Lomalta soils: are on linear coastal terraces are poorly drained Vertisols.
Sejita soils: are on linear coastal terraces and remain saturated for more than one month in normal years.

DRAINAGE AND PERMEABILITY: Well drained. Permeability is slow. Runoff is high on 1 to 5 percent slopes, and very high on 5 to 8 percent slopes. These soils are flooded rarely for very brief to brief periods during tropical storms.

USE AND VEGETATION: Used for livestock grazing or wildlife habitat. These soils are unsuitable for crop production. Vegetation consists of a sparse stand of stunted mesquite, spiny hackberry, leatherstem, prickypear, lovegrass tridens, Texas bristlegrass, hooded windmill, and various salt-tolerant species. The ecological site is Coastal Ridge, PE 31-44, R150BY647TX.

DISTRIBUTION AND EXTENT: Gulf Coast Saline Prairies (MLRA 150B in LRR T) in the lower coastal plain of southern Texas. The series is of small extent.

MLRA OFFICE RESPONSIBLE: Temple, Texas

SERIES ESTABLISHED: Cameron County, Texas; 1907.

REMARKS: Classification changed from Ustollic Camborthids to Typic Calciustepts 11/2000 based on typifying pedon description. Further study and characterization data of the series is needed to verify classification.
Diagnostic horizons and features recognized in this pedon are:

Ochric epipedon: 0 to 30 cm (0 to 12 in) (A horizon)
Calcic horizon: 30 to 56 cm (12 to 22 in) (Bk1 and Bk2 horizons)
Buried horizons: 94 to 203 cm (37 to 80 in) (Bkb1 and Bkb2 horizons)

ADDITIONAL DATA: none

TAXONOMIC VERSION: Keys to Soil Taxonomy, Tenth Edition, 2006