LOCATION GURABO PREstablished Series
TAXONOMIC CLASS: Clayey over loamy, mixed, active, isohyperthermic Aeric Epiaquerts
TYPICAL PEDON: Gurabo clay -- pasture. (Colors are for moist soil.)
Ap1--0 to 7 inches; very dark grayish brown (10YR 3/2) clay; weak fine granular structure; firm; slightly sticky, plastic; common fine black (10YR 2/1) grains; few fine rock fragments; common fine roots; field moisture 38.3 percent; common fine faint reddish brown (5YR 4/4) masses of iron accumulation; slightly acid; clear smooth boundary.
Ap2--7 to 12 inches; dark brown (10YR 3/3) clay; weak medium angular blocky structure; firm; slightly sticky, plastic; common fine black (10YR 2/1) grains; common fine roots; few fine rock fragments; faint pressure faces on surfaces of peds; field moisture 44.9 percent; common fine distinct yellowish brown (10YR 5/6) masses of iron accumulation; common fine distinct greenish gray (5GY 5/1) and few fine faint gray (10YR 5/1) areas of iron depletions; slightly acid; clear wavy boundary. (Combined thickness of the A horizons range from 4 to 15 inches in thickness.)
Bg--12 to 21 inches; grayish brown (10YR 5/2) clay; weak coarse angular blocky structure; firm; slightly sticky, plastic; few fine black (10YR 2/1) grains; common fine roots, flattened on primary surfaces; few fine rock fragments; many medium slickensides having polished and grooved surfaces; distinct pressure faces on surfaces of peds; field moisture 37.1 percent; common medium distinct greenish gray (5GY 6/1) and common fine faint gray (10YR 5/1) areas of iron depletions; slightly acid; gradual wavy boundary.
Bw--21 to 29 inches; about 50 percent dark yellowish brown (10YR 4/4) and about 50 percent yellowish brown (10YR 5/6) clay; weak medium and coarse angular blocky structure; firm; slightly sticky, plastic; few fine black (10YR 2/1) grains; few fine roots, flattened on primary surfaces; few fine rock fragments; common distinct slickensides having polished and grooved surfaces; distinct pressure faces on surfaces of peds; field moisture 31.0 percent; slightly acid; gradual wavy boundary.
2C--29 to 39 inches; mixed colors of the weathered rock fragments; rubbed color brown (10YR 5/3) clay loam; massive; friable; slightly sticky, slightly plastic; few fine black (10YR 2/1) grains; few fine roots, flattened on primary surfaces; few fine rock fragments; common faint slickensides having polished and grooved surfaces; faint pressure faces on surfaces of peds; slightly acid; gradual wavy boundary.
3C--39 to 48 inches; mixed colors of the weathered rock fragments; rubbed color brown (10YR 5/3) sandy loam; massive; very friable; nonsticky, nonplastic; few fine black (10YR 2/1) grains; slightly acid; gradual wavy boundary.
4C--48 to 62 inches; mixed colors of the weathered rock fragments; rubbed color yellowish brown (10YR 5/4) gravelly clay loam; weak coarse subangular blocky structure; friable; slightly sticky, slightly plastic; faint pressure faces on surfaces of peds; slightly acid; gradual wavy boundary.
5C--62 to 80+ inches; coarse-textured partially weathered igneous rock fragments.
TYPE LOCATION: Approximately 5 kilometers west of the town of Gurabo, about 200 meters north of kilometer marker 5.6 on Highway 30; Gurabo Experiment Station, Gurabo Municipio: Puerto Rico.
RANGE IN CHARACTERISTICS: Solum thickness ranges from 20 to 40 inches. Depth to consolidated bedrock is more than 60 inches. Reaction ranges from slightly acid to slightly alkaline throughout.
The A or Ap horizon has hue of 10YR, value of 4 to 6, and chroma of 1 to 3. Redoximorphic features in shades of yellow, brown, and gray range from few to many. Texture is clay loam or clay.
The Bw horizons have hue of 10YR or 2.5Y, value of 4 to 6, and chroma of 3 or 4; or there is no dominate matrix color and it is multicolored in shades of brown, yellow, and gray. Redoximorphic features in shades of yellow, brown, and gray range from few to many. Texture ranges from clay loam to clay.
The Bg horizons have hue of 10YR or 2.5Y, value of 4 to 6, and chroma of 1 or 2. Redoximorphic features in shades of yellow, brown, and gray range from few to many. Texture ranges from clay loam to clay.
The C horizons have hue of 10YR or 2.5Y, value of 4 to 6, and chroma of 1 to 4; or there is no dominate matrix color and it is multicolored in shades of brown, yellow, and gray. Redoximorphic features in shades of yellow, brown, and gray range from none to common. Texture ranges from sandy loam to clay loam and is frequently stratified.
COMPETING SERIES: There are no other known series in the same family.
GEOGRAPHIC SETTING: Gurabo soils are on alluvial fans. They formed in alluvial sediments derived from igneous rocks. Slopes range from 0 to 8 percent. The average annual temperature ranges from 73 to 77 degrees F., and the average annual rainfall ranges from 72 to 78 inches.
GEOGRAPHICALLY ASSOCIATED SOILS: These include Caguabo, Mabi, Montegrande, Mucara, and Rio Arriba soils. The well drained Caguabo and Mucara soils are on adjacent uplands. In addition, Caguabo soils are shallow to bedrock and Mucara soils are moderately deep. Mabi, Montegrande, and Rio Arriba soils are on slightly higher positions. In addition, Mabi soils have smectitic mineralogy, Montegrande soils are moderately well drained, and Rio Arriba soils are moderately well drained and have argillic horizons.
DRAINAGE AND PERMEABILITY: Somewhat poorly drained; slow permeability.
USE AND VEGETATION: Most areas of Gurabo soils are used for pasture or cropland. Some areas have reverted to intermittent woodland by natural revegetation. Vegetation includes pangola grass, guinea grass, and other native and introduced plants, shrubs, and trees.
DISTRIBUTION AND EXTENT: Alluvial fans in north and central parts of Puerto Rico. The series is of small extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Raleigh, North Carolina.
SERIES ESTABLISHED: Puerto Rico; 1972.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Ochric Epipedon - zone from 0 to 12 inches (Ap1 and Ap2 horizons).
Cambic Horizon - zone from 12 to 29 inches (Bg and Bw horizons).
Water Table - 6 to 15 inches; perched.
ADDITIONAL DATA: Characterization pedon-Gurabo Municipio, Puerto Rico. S63PR-16-1 and published in SSIR Report No. 12. Sample by NSSL, Lincoln, NE.; 1967.
MLRA: 270.