LOCATION TABECHEDING GU+HI PB PWEstablished Series
TAXONOMIC CLASS: Fine, halloysitic, isohyperthermic Aquic Tropudults
TYPICAL PEDON: Tabecheding silty clay loam - on a 5 percent east-facing, slightly convex slope in a wetland savannah. (Colors are for moist soil. Texture of the surface layer is an apparent field texture.)
A1--0 to 7 inches; 70 percent olive brown (2.5Y 4/4) silty clay loam; many fine and medium faint mottles of light olive brown (2.5Y 5/4); moderate fine granular structure in the upper .9 inch over moderate medium subangular blocky structure parting to moderate fine subangular blocky; friable, slightly sticky and slightly plastic; common very fine and fine roots, and few medium and coarse roots; many very fine and common fine tubular and interstitial pores; 2 to 4 percent angular uncoated quartz sand grains .04 inch in diameter; extremely acid (pH 4.2, 1:1 water); clear smooth boundary. (5 to 7 inches thick)
B2t--7 to 14 inches; brownish yellow (10YR 6/6) clay; few fine distinct light brownish gray (10YR 6/2) and few fine faint yellowish brown (10YR 5/6) mottles; moderate medium prismatic structure parting to moderate fine subangular and angular blocky; friable, sticky and plastic; common very fine and fine roots; many very fine and common fine tubular pores within interstices and vesicular pores; common thin coatings on faces of peds and lining tubular pores; many pressure faces; extremely acid (pH 4.0, 1:1 water); clear irregular boundary. (6 to 10 inches thick)
B3t--14 to 20 inches; brownish yellow (10YR 6/6) clay; many fine distinct light gray (10YR 7/2) mottles, common fine distinct yellowish brown (10YR 5/8) mottles and few fine distinct yellowish red (5YR 4/6) mottles; weak medium prismatic structure parting to moderate very fine and fine angular blocky; firm, sticky and plastic; few very fine, fine, and medium roots; many very fine and fine tubular and vesicular pores; few thin coatings on faces of peds, common pressure faces; extremely acid (pH 4.0, 1:1 water); gradual irregular boundary. (2 to 8 inches thick)
C1--20 to 24 inches; light gray (10YR 7/2) clay; common medium distinct yellowish brown (10YR 5/8) mottles, and few medium prominent red (2.5YR 4/6) mottles; weak medium and coarse prismatic structure; firm, sticky and plastic; few very fine, fine, and medium roots; many very fine and fine tubular pores; common pressure faces; extremely acid (pH 4.0, 1:1 water); clear smooth boundary. (8 to 20 inches thick)
C2--34 to 41 inches; reddish gray (5YR 5/2) clay; common medium distinct strong brown (7.5YR 5/8) mottles; weak medium and coarse prismatic structure; firm, sticky and plastic; few very fine and fine roots; common very fine tubular pores; common pressure faces; common medium distinct black (7.5YR 2/1) masses of lignite; extremely acid (pH 4.0; 1:1 water); abrupt smooth boundary. (0 to 10 inches thick)
IIC3g--41 to 62 inches; about 60 percent dark gray (10YR 4/1) clay finely interbedded with about 40 percent very dark gray (10YR 3/1) lignite; moderate medium platy structure parting to strong thin platy; firm, sticky and plastic; common very fine and fine roots, and few medium roots; common very fine and fine tubular and interstitial pores; few thin oxidized iron stains lining some tubular pores within interstices; lignite bed is tilted at a 6 degree dip to the south and a 14 degree dip to the east by northeast; extremely acid (pH 3.2, 1:1 water).
TYPE LOCATION: Airai Municipality, Babelthuap Island, Palua, Western Caroline Islands; about 3,050 feet E. and 590 feet S. of the SE. end of the dam at Ngerimel Reservoir; N. on the road to Nekken about .9 mile past water tank, continue on road about one-half the distance to the bottom of the hill beyond first 90 degree left turn, then turn right 90 degrees and proceed 597 feet; lat. 7 degrees 22 minutes 3.6 seconds N. and long. 134 degrees 32 minutes 45 seconds E.
RANGE IN CHARACTERISTICS: The solum is 15 to 22 inches thick. A perched water table is at a depth of 15 to 35 inches throughout the year.
The A horizon has moist color of 2.5Y 3/2 or 4/4, of 5Y 4/3, or of 10YR 3/2 and has mottles of 2.5Y 5/4 or of 10YR 5/4 or 5/6.
The Bt horizon has moist color of 10YR 5/6 or 6/6, or of 5Y 7/2 and has few to many mottles of 10R 4/6, of 5YR 4/6, of 7.5YR 5/8, or of 10YR 5/6, 6/2, 6/4, 6/6, 7/1, or 7/2. It has an apparent field texture of silty clay loam, silty clay, or clay. Some pedons are as much as 15 percent by volume solid, spherical iron concretions .08 to .4 inch in diameter. Base saturation is less than 5 percent. Aluminum saturation is more than 85 percent.
The C horizon has moist color of 2.5YR 7/4, of 5YR 5/2, of 10YR 3/1, 4/1 or 7/2, or of 5Y 6/1 or 6/3 with few to many 10R 3/6, 4/6, or 4/8, of 2.5YR 4/6 or 5/8, of 5YR 5/8, of 7.5YR 5/8 or 2/0, of 10YR 5/8, or of 5Y 7/6 mottles. The apparent field texture is clay or silty clay. Some pedons contain interbedded lignite in the C horizon or up to 15 percent small, solid, spherical pebble size iron concretions.
COMPETING SERIES: This is the Corozal series in a different family. Corozal soils have mixed mineralogy and formed in sandy sediments.
GEOGRAPHIC SETTING: Tabecheding soils are on dissected marine terraces and formed in residuum derived from bedded marine clay deposits. Slopes are 2 to 30 percent. The elevation is 13 to 164 feet. The mean annual rainfall is about 145 inches, and the mean annual temperature is 81 degrees F.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Aimeliik, Babelthuap, Ngardmau, Ngatpang, and Palau series. These soils, with the exception of the Ngatpang soils, are well drained upland soils formed in residuum derived from highly weathered volcanic rock. Aimeliik is under forest vegetation, Palau under anthropic savannah, and Babelthuap and Ngardmau under degraded anthropic savannah. Babelthuap and Ngardmau soils contain 30 to 75 percent ferritic and gibbsitic concretions. Ngatpang soils formed in marine terrace deposits but are moderately well drained and have an oxic horizon.
DRAINAGE AND PERMEABILITY: Somewhat poorly drained; slow through rapid runoff; very slow permeability.
USE AND VEGETATION: Most of these soils are in idle land which has reverted to an anthropic savannah and is used for watershed. Present vegetation is Ischaemum digitalum, Rhynchospora rubra, Dianella ensifolia, Hedyotis fruticulosa and Lindsaea ensifolia.
DISTRIBUTION AND EXTENT: Airai Municipality, island of Babelthuap. This series is of small extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California
SERIES ESTABLISHED: Island of Babelthuap, Palau, Western Caroline Islands, 1981.
REMARKS: Laboratory data indicates that the C horizon has a high shrink-swell potential (COLE = 0.155 for C1). However, due to very high moisture conditions of both in situ and disturbed samples, shrink-swell potential should be rated moderate, except where interpretation for pottery is concerned.
Local pronunciation of the word Tabecheding is "Tabeding."