Keys to Soil Taxonomy: Suborders

Code	Name	Description
AA	Histels	Gelisols that have organic soil materials that meet one or more of the following: Overlie cindery, fragmental, or pumiceous materials and/or fill their interstices and directly below these materials have either a densic, lithic, or paralithic contact; or When added with the underlying cindery, fragmental, or pumiceous materials, total 40 cm or more between the soil surface and a depth of 50 cm; or Are saturated with water for 30 or more cumulative days during normal years (or are artificially drained) and have 80 percent or more, by volume, organic soil materials from the soil surface to a depth of 50 cm or to a glacic layer or a densic, lithic, or paralithic contact, whichever is shallowest.
AB	Turbels	Other Gelisols that have one or more horizons showing cryoturbation in the form of irregular, broken, or distorted horizon boundaries, involutions, the accumulation of organic matter on top of the permafrost, ice or sand wedges, and oriented rock fragments.
AC	Orthels	Other Gelisols.

Source: Keys to Soil Taxonomy, Eighth Edition. 1998.