LOCATION MAHO BAY VIEstablished Series
TAXONOMIC CLASS: Loamy, mixed, superactive, isohyperthermic, shallow Typic Haplustolls
TYPICAL PEDON: Maho Bay gravelly loam. (Colors for moist conditions.)
A--0 to 7 inches; very dark brown (10YR 2/2) gravelly loam, weak coarse granular structure; friable; many fine roots, common medium roots, few coarse roots; many fine and medium wormcasts; about 15 percent, by volume, pebbles; slightly acid; clear wavy boundary. (2 to 10 inches thick)
Bw--7 to 11 inches; dark brown (10YR 3/3) gravelly loam; moderate very fine and fine subangular blocky structure; friable; common fine and medium roots; common fine and medium wormcasts; about 30 percent, by volume, pebbles; very strongly acid; clear wavy boundary. (2 to 10 inches thick)
Cr--11 to 22 inches; dark brown (10YR 4/3) saprolite that has a silt loam texture; massive; common fine roots, few medium roots; very strongly acid; clear wavy boundary. (2 to 20 inches thick)
R--22 to 60 inches; brown (10YR 5/3) unweathered igneous bedrock.
TYPE LOCATION: St. John Island, U.S. Virgin Islands. From intersection of VI-10 and VI-206, about 1.3 miles east on VI-10 (Centerline Road), about 250 feet northeast of Centerline Road, on a shoulder in Maho Bay Watershed. Western St. John quadrangle; lat. 18 degrees 21 minutes 0 seconds N.; long. 64 degrees 44 minutes 44 seconds W.; PRD 1940.
RANGE IN CHARACTERISTICS: Depth to saprolite ranges from 8 to 20 inches. Reaction ranges from strongly acid to neutral in the A horizon, and very strongly acid to slightly acid in the Bw horizon.
The A horizon has hue of 7.5YR or 10YR, and value of 2 or 3, and chroma of 2 or 3. Texture is loam or clay loam in the fine-earth fraction. Content of pebbles and cobbles ranges from 0 to 30 percent, by volume.
The Bw horizon has hue of 7.5YR or 10YR, value of 3 to 5, and chroma of 2 to 4. Texture is loam or clay loam in the fine-earth fraction. Content of pebbles and cobbles ranges from 0 to 30 percent, by volume.
The Cr horizon is saprolite.
The R horizon is unweathered igneous bedrock.
COMPETING SERIES: There are no competing series in the same family.
GEOGRAPHIC SETTING: Maho Bay soils are on summits and side slopes of volcanic hills and mountains. They formed in material weathered from basic volcanic rock. Slopes range from 12 to 90 percent. The climate is tropical semiarid. The average annual air temperature ranges from 76 to 82 degrees F., and the mean annual precipitation is about 40 inches.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Annaberg, Cramer, Dorothea, Fredriksdal, Southgate, Susannaberg, and Victory soils. All of these soils are on similar positions of volcanic uplands. In addition, Annaberg soils have loamy-skeletal particle-size control sections. Cramer soils are clayey. Dorothea, Fredriksdal, and Susannaberg soils have more than 35 percent clay in the particle-size control section and have vermiculitic clay mineralogy. Southgate soils have loamy-skeletal particle-size control sections and do not have a Mollic epipedon. Victory soils are moderately deep to bedrock and do not have a mollic epipedon.
DRAINAGE AND PERMEABILITY: Well drained; moderate permeability.
USE AND VEGETATION: Most areas are in rangeland. The vegetation consists primarily of guina grass and buffelgrass.
DISTRIBUTION AND EXTENT: U.S. Virgin Islands. They are moderately extensive.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Raleigh, North Carolina
SERIES ESTABLISHED: St. John Island, USVI, 1995.
REMARKS: Diagnostic horizons and other features recognized in this pedon include:
Mollic epipedon - zone from 0 to 11 inches (A and Bw horizons).
Paralithic contact - the contact at 11 inches (Cr horizon).
Lithic contact - the contact at 22 inches (R horizon).
ADDITIONAL DATA: Characterization pedon - St. John Island, U.S. Virgin Islands; S91VI-20-11. Additional characterization pedon - St. John Island, U.S. Virgin Islands; S91VI-20-12. Samples by NSSL, Lincoln NE. 1991.
MLRA: 271.
SIR = VI0014