LOCATION NGARDOK PW+PBInactive Series
TAXONOMIC CLASS: Very-fine, mixed, isohyperthermic Typic Acroperox
TYPICAL PEDON: Ngardok silt loam - on an 18 percent slope in an anthropic savannah. When described (11/29/79), the soil was moist throughout. (Colors are for moist soil. All textures are apparent field textures.)
A1--0 to 2 inches; dark yellowish brown (10YR 3/4) silt loam; moderate medium subangular blocky structure; friable, slightly sticky and slightly plastic; many very fine, common fine and few medium roots; common very fine and few fine interstitial pores; common thin coatings on faces of peds and lining pores; approximately 2 percent by volume irregular blocky ferritic concretions .4 to .9 inch in size; very strongly acid (pH 4.6, 1:1 water); gradual smooth boundary. (2 to 6 inches thick)
B1--2 to 7 inches; brown (7.5YR 4/4) silty clay loam; moderate medium subangular blocky structure parting to moderate very fine and fine subangular block; friable, sticky and slightly plastic; many very fine roots and common fine roots; common very fine and few fine interstitial pores; continuous thin coatings on faces of peds and lining pores; approximately 3 percent by volume irregular blocky ferritic concretions and 2 percent gibbsite concretions .2 to .9 inch in size; very strongly acid (pH 4.8, 1:1 water); gradual wavy boundary. (4 to 8 inches thick)
B2--7 to 27 inches; strong brown (7.5YR 4/6) silty clay loam; moderate medium subangular blocky structure parting to moderate very fine and fine subangular blocky; friable, sticky and slightly plastic; few very fine and fine roots; many very fine and few fine interstitial pores and common very fine vesicular pores; continuous thin coatings on faces of peds and lining pores; approximately 3 percent by volume irregular blocky ferritic and 3 percent gibbsitic concretions .2 to 1 inch in size; strongly acid (pH 5.3, 1:1 water); clear wavy boundary. (10 to 23 inches thick)
B3--27 to 32 inches; 60 percent brown (7.5YR 4/4) silty clay loam and 40 percent dusky red (10R 3/4) saprolite crushing easily to silt loam; moderate medium subangular blocky structure; friable, sticky and slightly plastic; many very fine and few fine interstitial pores and common very fine vesicular pores; common thin coatings on faces of peds and lining pores; strong brown (7.5YR 5/6) coatings; approximately 8 percent by volume indurated saprolite fragments .4 to 2 inches in size; black (7.5YR 2/1) manganese veins and light brown (7.5YR 6/4) material along horizontal bedded planes in the saprolite fragments; strongly acid (pH 5.2, 1:1 water); gradual wavy boundary. (4 to 12 inches thick)
C--32 to 59 inches; dusky red (10R 3/4) silt loam; massive; friable, sticky and slightly plastic; many very fine and common fine vesicular pores; approximately 8 percent by volume indurated saprolite fragments .4 to 2 inches on size; common thin strong brown (7.5YR 5/6) coatings along fracture faces of saprolite; black (7.5YR 2/1) manganese veins and light brown (7.5YR 6/4) material along horizontal bedded planes in the saprolite; strongly acid (pH 5.4, 1:1 water).
TYPE LOCATION: Ngaremlengui Municipality, Babelthuap Island, Palau, Western Caroline Islands; about .2 mile up the channel at Algongui, take the right fork another .5 mile to the first clearing on the mainland, then about 147 feet S. of the channel; lat. 7 degrees 31 minutes 36 seconds N. and long. 134 degrees 31 minutes 43.5 seconds E.
RANGE IN CHARACTERISTICS: Thickness of the solum ranges from 20 to 39 inches.
The A horizon has moist color of 7.5YR 3/4, or of 10YR 3/3, 3/4, 4/3, or 4/4. The apparent field texture is silt loam or silty clay loam. The horizon is 0 to 15 percent ferritic and gibbsitic concretions .2 inch to 1 inch in size.
The B2 horizon has moist color of 5YR 4/4 or 4/6 or of 7.5YR 4/4 or 4/6. The apparent field texture is silt loam or silty clay loam. The amount of clay, as measured (2.5 X 15-bar water) is more than 75 percent. The horizon is 0 to 10 percent ferritic and gibbsitic concretions .2 inch to 2 inches in size. Reaction in 1:1 water is strongly acid or very strongly acid.
The C horizon has moist color of 10R 3/3, 3/4, 3/6, 4/3, or 4/4 and has layers of interbedded tuffaceous material that has moist color of 7.5YR 6/4, 5/4, 5/8, 4/2, 4/4, 3/4, or 2/1. The apparent field texture is silt loam or silty clay loam. The horizon is 5 to 15 percent indurated saprolite fragments .2 to 3 inches in size. Reaction is very strongly acid or strongly acid.
COMPETING SERIES: These are the Gagil, Ngatpang, and Palau series. Gagil soils are degraded and have an oxidic mineralogy and very low fertility. Ngatpang and Palau soils have halloysitic mineralogy.
GEOGRAPHIC SETTING: Ngardok series on hills that have convex relief. Slopes are 2 to 75 percent. The soils formed in highly weathered volcanic tuff. Elevation ranges from 0 to 459 feet. The mean annual temperature is 81 degrees F. and does not vary by more than 34 degrees F from month to month. Mean annual maximum temperature is 88 degrees F. and mean annual minimum temperature is 75 degrees F. The mean annual rainfall is 145 inches and varies from 130 to 183 inches from year to year with the driest months (February, March and April) averaging 7 to 9 inches per month.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Aimeliik and the competing Palau soils. Aimeliik soils have halloysitic mineralogy.
DRAINAGE AND PERMEABILITY: Well drained; slow through very rapid runoff; moderately rapid permeability.
USE AND VEGETATION: Most of these soils are under tropical rain forest vegetation and are used for hunting, watershed, and a minor amount of timber harvesting. A few areas are under anthropic savannah vegetation.
DISTRIBUTION AND EXTENT: Island of Babelthuap. This series is of small extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California
SERIES ESTABLISHED: Ngaremlengui Municipality, Babelthuap Island, Palau, Western Caroline Islands, 1981.
REMARKS: These soils are more erosive than the geographically associated Aimeliik and Palau soils, especially in the underlying saprolite.
ADDITIONAL DATA: National Soil Survey Lab Data No. S79 TQ-632-11.