consolidated material (excluding cemented or indurated pedogenetic
horizons)
very low effective CEC and/or acting as anion exchanger
saturated with groundwater (or upwards moving gases) long enough that
reducing conditions occur
carbonates derived from the soil solution and precipitated in the soil
(secondary carbonates), less pronounced than in calcic or petrocalcic
horizons
low rH value and/or presence of sulfide, methane or reduced Fe
open and close due to swelling and shrinking of clay minerals
relatively low CEC
saturated with surface water (or intruding liquids), at least temporarily,
long enough that reducing conditions occur