Re: Master horizon for fill

The L, co, di, and ma designations were recently approved for use. The definitions are not in any published reference. The following definitions will be in the next edition of the Field Book for Describing and Sampling Soils.

L layers: Limnic horizons or layers include both organic or mineral soil materials that were either (1) deposited in water by precipitation or through the actions of aquatic organisms, such as diatoms, or (2) derived from underwater and floating aquatic plants and subsequently modified by aquatic animals. They include coprogenous earth, (sedimentary peat), diatomeous earth, and marl. (Soil Survey Staff, 1999). L horizons or layers do not use the subordinate distinctions used with the other master horizons and layers. They use only the following subordinate distinctions: co, di, or ma.

co
Coprogenous earth
This symbol is used only with ""L"" to indicate a limnic layer of coprogenous earth (or sedimentary peat).

di
Diatomaceous earth
This symbol is used only with ""L"" to indicate a limnic layer of diatomaceous earth.

ma
Marl
This symbol is used only with ""L"" to indicate a limnic layer of marl.