Micromorphology of a clayey Bs horizon in an ash-derived podzolic soil from shimokita peninsula in northeastern Japan

It is well known that most developed Podzols or Spodosols occur on coarse- textured materials with a low content of weatherable minerals (Duchaufour 1977; McKeague et al 1983). In the Podzols derived from such parent material*. the th and/or Bhs horizons show definite evidence of illuviation characterized by continuous cementation, presence of cracked coatings on sand grains, and/or distinct dark pellets, These features were, therefore, adopted as the morphological criteria for spodic horizons in the Soil Taxonomy (Soil Survey Stalt 1975). The problem is to determine whether such criteria can be applied to Podzolic soils derived from volcanic ash which consists of fine, weatherable minerals.