Fragipan

They are altered subsurface soil layers that restrict water flow and root penetration.In soil descriptions, they are commonly denoted by a Bx or Btx symbol.[2] The Required Characteristics of a fragipan according to the "Keys to USDA soil taxonomy, tenth edition, 2006" are What this means in plain English is The genesis of fragipans is open to considerable debate.Some fragipans inherit their properties from buried soils called paleosols.It has been proposed that fragipans form by hydroconsolidation, that is the collapse of the soil structure due to loading and wetting.
frangipanefrangipanihorizonUSDA soil taxonomyduripanpedogenesisparent materialsoil structurePetrocalcic Horizoncalcium carbonatemagnesium carbonatepleistocenepaleosolsHardpan