Great Groups of the Solonetzic Order
The three main great groups of the Solonetzic Order are based on a developmental sequence. In the Solonetz Great Group, the Bn or Bnt horizon is directly overlain by an Ah or Ap horizon. Chemical weathering of the top of the Bn or Bnt horizon leads to development of a grayish Ae horizon, diagnostic of the Solodized Solonetz Great Group. Further weathering leads to disintegration of the Bnt and formation of a transitional AB or BA horizon, diagnostic of the Solod Great Group. Finally, high sodium soils in heavy clay sediments are classified into the Vertic Solonetz Great Group.
Soils of the Solonetz Great Group have a Bn or Bnt horizon and either have no Ae horizon or one that is less than 2 cm thick.
Solodized Solonetz Soils:
Solodized Solonetz soils have an Ae horizon greater than 2 cm deep and an intact Bnt or Bn horizon.
In the Solod Great Group the Bn or Bnt has been further weathered, leading to formation of a transitional AB or BA horizon.
Soils of this Great Group occur on heavy clay deposits and have the chemical characteristics of the Solonetzic Order and the presence of slickensides (i.e., polished surfaces along fracture planes in the soil).