LOCATION SAN SEBASTIAN PREstablished Series
TAXONOMIC CLASS: Clayey-skeletal, carbonatic, isohyperthermic Calcic Argiudolls
TYPICAL PEDON: San Sebastian gravelly clay-weeds. (Colors are for moist soil)
Ap--0 to 4 inches; dark brown (10YR 3/3) gravelly clay, moderate fine and medium granular structure; friable, slightly sticky, plastic; many fine roots; slight effervescence; clear wavy boundary. 3 to 6 inches thick.
Bk1--4 to 9 inches; strong brown (7.5YR 5/6) very gravelly clay; weak medium subangular blocky structure; firm, sticky, plastic; few fine roots; few faint clay films; clay coatings on gravel faces; slight effervescence; from 50 to 60 percent by volume of gravel; clear smooth boundary. 4 to 7 inches thick.
Bk2--9 to 14 inches; strong brown (7.5YR 5/6) extremely gravelly clay; weak medium subangular blocky structure; firm, sticky, plastic; few fine roots; few faint clay films; clay coatings on gravel faces; strong effervescence; more than 60 percent by volume of gravel; clear smooth boundary 4 to 8 inches thick.
BC--14 to 22 inches; reddish yellow (7.5YR 6/8) extremely gravelly clay; weak fine subangular blocky structure; firm, sticky, plastic; clay coatings on gravel faces; strong effervescence; more than 60 percent by volume of grave; gradual wavy boundary. 7 to 11 inches thick.
C1--22 to 33 inches; reddish yellow (7.5YR 7/6) very gravelly clay; massive; friable; sticky and plastic; strong effervescence; from 50 to 60 percent by volume of gravel; gradual wavy boundary. 9 to 13 inches thick.
C2--33 to 41 inches plus; reddish yellow (7.5YR 7/6) gravelly clay; massive; friable; slightly sticky, plastic; from 25 to 60 percent by volume of gravel; strong effervescence.
TYPE LOCATION: Culebrinas SCD, Puerto Rico, 5 miles northwest of the town of San Sebastian; 250 meters east of kilometers marker 9.2 of Highway 112.
RANGE IN CHARACTERISTICS: Thickness of the solum ranges from 29 to 32 inches. These soils are calcareous throughout. Fine to medium gravel is present throughout the profile. These soils have slightly sticky and plastic A horizons and sticky and plastic Bk and C horizons. Base saturation (by sum of cations) is more than 60 percent at 50 inches below the top of the argillic horizon. CEC is more than 24 meq/100 grams of clay in the major part of the argillic horizon. Coarse fragments exceeds 35 percent, by volume, throughout the major part of the control section.
The A horizons have colors in hues of 7.5YR and 10YR, values of 3 and 4, and chromas of 2, 3 and 4.
The Bk horizons range in hues of 7.5YR to 10YR, values of 4 to 5, and chromas of 4 to 8. Texture of the soil is gravelly clay throughout. Structure ranges from weak fine to medium subangular blocky.
COMPETING SERIES: These are the Juncal and Machete series int he same Subgroup and the Tanama and Rio Arriba series in the same Great Group. The Juncal and Machete soils lack the coarse fragments in their profiles and are not calcareous. The Tanama soils have hard rock within 20 inches of the surface. The Rio Arriba soils have horizons with COLE values greater than 0.09 and crack when dry.
GEOGRAPHIC SETTING: The San Sebastian series are on moderately steep to steep sideslopes with slope gradients from 20 to 60 percent. The regolith consists of fine textured gravelly residuum from limestone. The climate is humid tropical.
The average annual precipitation is 85 inches and the mean annual temperature 77 degrees F. The mean annual soil temperature at 20 inches is more than 72 degrees F. and the difference between mean summer and winter temperatures is less than 9 degrees F.
GEOGRAPHICALLY ASSOCIATED SOILS: This is the competing Juncal in addition to Colinas and Cidral series. The Colinas soils are shallower, darker, and lack argillic horizons. The Cidral soils are redder, acid, and free of gravel throughout.
DRAINAGE AND PERMEABILITY: Well drained, rapid runoff and moderate permeability.
USE AND VEGETATION: Most of the acreage is in brush. Small areas are in sugar cane and native pasture.
DISTRIBUTION AND EXTENT: Humid limestone uplands of Puerto Rico. The series is of moderate extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Raleigh, North Carolina
SERIES ESTABLISHED: Culebrinas SCD, Puerto Rico. Name is from a town where the series was first recognized.
REMARKS: The classification was updated with the 4/91 draft from CLayey-skeletal, carbonatic, isohyperthermic Typic Tropudalfs to Clayey-skeletal, carbonatic, isohyperthermic Eutropeptic Rendolls based on lab data from the Type Location. The previous OSED date was 4/67.
This soil was formerly included in the Tanama series.
Diagnostic horizons and features recognized in the pedon:
Mollic epipedon - zone from 0 to 9 inches (Ap and Bk1 horizons)
Calcic horizon - zone from 4 to 22 inches (Bk horizons)