Re: manganese concretions

There is evidence that manganese segregations form quite rapidly under alternating reducing and oxidizing conditions. Most of the evidence is from rice paddy soils. The generally accepted theory is that the rings or layers in a concretion represent the addition of layers over time. The segregations begin to form after a few decades under paddy rice culture.

The ""w"" suffix symbol is generally not used with other suffix symbols. The ""w"" should have ""little or no apparent illuvial accumulation of material."" The ""c"" is used for ""a significant accumulation of concretions or nodules."" Thus a Bc would be the preferred horizon designation.