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Gelic materials (Figure 48).

Gelic materials.—Diagnostic soil material recognized in mineral and organic soils that are subject to intense cryoturbation. Many of these soils are affected by permafrost. Gelic materials are identified either in the freeze-thaw active layer, commonly just above the permafrost and/or in the upper part of the permafrost. In some cases there is no permafrost within 200 cm of the soil surface. Gelic materials are formed by cryopedogenic processes and can be identified by either macro- or micromorphological properties. Macromorphological evidence includes irregular and broken horizons, involutions, accumulation of organic matter on top of and within the permafrost, oriented rock fragments, silt enriched layers, and ice segregation forms (such as lenses, vein ice, ice wedges, and segregated ice crystals). Micromorphological evidence includes the micro fabric forms “orbiculic,” “conglomeric,” “banded,” and “vesicular.” The presence of gelic materials is a criterion used in the taxonomic keys. Depending on the depth to gelic materials, their presence is used to identify soils of the Gelisols order; Turbels suborder; and Turbic subgroups within some Andisols, Inceptisols, Mollisols, and Spodosols. See active layer and cryoturbation.

 

Figure 48.—Soil profile and landscape of a Glacistel in Alaska with a permanently frozen ice layer (designated “Wf”) between depths of 55 and 105 cm. Soils with gelic materials may also have a glacic layer composed of massive ice or ground ice in the form of ice lenses or wedges. Where present, the glacic layer is 30 cm or more thick and contains 75 percent or more visible ice.

 

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Uploaded on January 1, 2025