Re: Master horizon for fill (C is taken!)

The definition of the ""C"" horizon designation (Soil Survey Manual, 1993) is as follows:

""C horizons or layers: Horizons or layers, excluding hard bedrock, that are little affected by pedogenic processes and lack properties of O, A, E, or B horizons. The material of C layers may be either like or unlike that from which the solum presumably formed. The C horizon may have been modified even if there is no evidence of pedogenesis.

Included as C layers are sediment, saprolite, unconsolidated bedrock, and other geologic materials that commonly are uncemented (table 3-14) and exhibit low or moderate excavation difficulty (table 3-21). Some soils form in material that is already highly weathered. If such material does not meet the requirements of A, E, or B horizons, it is designated C. Changes not considered pedogenic are those not related to overlying horizons. Layers that have accumulations of silica, carbonates, or gypsum or more soluble salts are included in C horizons, even if indurated (table 3-14). If the indurated layers are obviously affected by pedogenic processes, they are a B horizon.""

It is clear in the definition that the intent is to include pre-weathered material and saprolite in the ""C"" horizon concept. The intent is to assign ""C"" to all layers that fail to meet the criteria for other designations. Saprolite does present a unique problem as it has undergone much change and the distinction between a B and C horizon in such material is based almost exclusively on ""rock structure"" another nebulous term.

Some scientists have suggested we add a new master horizon, such as ""F"" for fill material. You may be interested in visiting the site of the ""International Committee on the Classification of Anthropogenic Soils"" (ICOMANTH):

http://wwwscas.cit.cornell.edu/icomanth/