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Clay Minerals, Humus Complexes, and Classification of Four “Andepts” of Maui, Hawaii

1986; Wiley; Volume: 50; Issue: 4 Linguagem: Inglês

10.2136/sssaj1986.03615995005000040035x

1435-0661

Kōji Wada, Yasuko Kakuto, H. Ikawa,

Geology and Paleoclimatology Research

Abstract Clay minerals and humus complexes in the Pane, Kula, Kaipoioi, and Olinda soils, derived from basalt‐andesitic to andesitic volcanic ash on Maui, Hawaii, were studied by a combination of methods. These soils have ustic soil moisture regimes except for the Olinda, which has an udic moisture regime. The clay content of all soil samples was high (35‐73%). Allophane and/or noncrystalline Fe oxides were abundant in the Pane, Kula, and Kaipoioi soils, but they were not identified or were present only in small amounts in the Olinda soil. In the Olinda soil, layer silicates, largely of eolian origin, and hematite were major clay components. Substantial amounts of halloysite and imogolite were found in the surface and subsurface horizons, respectively, of the Pane soil. Maghemite or hematite and magnetite were major silt and fine sand components in all samples and the content of weatherable minerals was <10% except for the Kaipoioi soil. Iron and Al bound with humus increased in the soils in the order of Pane <Kula <Kaipoioi Olinda, showing an inverse relation with formation of allophane and noncrystalline Fe oxides. The organic matter inhibits the formation of allophane and imogolite by lowering of activity of Al through formation of metal‐ligand bonds. Using the U.S. system of soil taxonomy, the sampled Pane soil is classified as an Eutrandept, and the sampled Kula and Kaipoioi soils as Dystrandepts, while the sampled Olinda soil is not classified as an Andept. In the Andisol proposal, the Pane, Kula, and Kaipoioi soils would be classified as Haplustands, while the Olinda would be Hapludand. These taxonomic names require further consideration regarding the definition of the great groups or suborders of Andisols.