An absolute enrichment with iron oxides can occur in situations where intermittent wetness from a fluctuating water table gives rise to the reduction and mobilization of iron and its migration and reprecipitation as mottles, nodules, concretions and vesicular cement (ferricrete). A warm, sub-humid to humid climate with a distinct dry season is commonly associated with plinthite formation.
Strongest expression occurs in middle to lower slope positions in the landscape. Old erosion surfaces may be preserved by a capping of plinthite (also termed laterite). Manganese is associated with iron in some plinthic materials (Soil forms: Longlands, Wasbank, Westleigh, Dresden, Avalon, Glencoe, Bainsvlei).