Gleysol (G)
Soils of this great group have the general properties specified for soils of the Gleysolic order, but they lack a well-developed, mineral-organic surface horizon. They occur commonly in poorly drained positions in association with soils of several other orders.
Gleysols lack an Ah or Ap horizon as specified for Humic Gleysols. They also lack a Bt horizon. They may have either an Ah horizon thinner than 10 cm or an Ap horizon with one of the following properties:
- It contains less than 2% organic carbon.
- It has a rubbed color value greater than 3.5 (moist) or greater than 5.0 (dry).
- It shows little contrast in color value with the underlying layer (a difference of less than 1.5 units if the value of the underlying layer is 4 or more, or a difference of less than 1 unit if that value is less than 4).
These soils have a gleyed B or C horizon, and they may have an organic surface horizon.
The great group is divided into five subgroups based on the kind of horizons and their sequence.
Vertic Gleysol (V.G)
Common horizon sequence: LFH or O, Bg or Bgvj, Bgss or Cgss, Cg
These soils have the general properties specified for the Gleysolic order and the Gleysol great group. They may have any horizons in the upper solum common to other subgroups within the Gleysol great group. However, they differ from other subgroups by having properties indicative of intergrading to the Vertisolic order. Specifically, they have a slickenside horizon (Bgss or Cgss), the upper boundary of which occurs within 1 m of the mineral soil surface. They may also have a weak vertic horizon (Bgvj).
Solonetzic Gleysol (SZ.G)
Common horizon sequence: LFH or O, Aeg, Bng, Cgsk
These soils have the general properties specified for the Gleysolic order and the Gleysol great group. They also have a solonetzic B horizon and may have a Bgf horizon. Typically, they have saline parent materials.
Fera Gleysol (FE.G)
Common horizon sequence: LFH or O, Aeg, Bgf, Cg
These soils have the general properties specified for the Gleysolic order and the Gleysol great group. They also have a Bgf horizon at least 10 cm thick and lack a solonetzic B horizon. The Bgf horizon contains accumulated hydrous iron oxide (dithionite extractable), which is thought to have been deposited as a result of the oxidation of ferrous iron. The Bgf horizon usually has many prominent mottles of high chroma.
Orthic Gleysol (O.G)
Common horizon sequence: LFH or O, Bg, Cg
These soils have the general properties specified for the Gleysolic order and the Gleysol great group. Typically, they have strongly gleyed B and C horizons and may have organic surface horizons and an eluvial horizon. Orthic Gleysols are identified by the following properties:
- They have a B horizon (Bg or Btjg) at least 10 cm thick.
- They may have an Ah or Ap horizon as specified for the Gleysol great group.
- They have neither a Btg horizon, nor a solonetzic B horizon, nor a Bgf horizon at least 10 cm thick.
Rego Gleysol (R.G)
Common horizon sequence: LFH or O, Cg
These soils have the general properties specified for the Gleysolic order and the Gleysol great group. They differ from Orthic Gleysols in that they lack a B horizon at least 10 cm thick. They thus consist of a gleyed C horizon, with or without organic surface horizons, and a thin Ah or B horizon.
Note: Diagnostic horizons are underlined.