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This paper offers an alternative to the current definition of a buried soil (Soil Survey Staff 1975), stressing criteria that are more amenable to paleopedology. We suggest that any measurable depth of sediment buries a soil and that the soil remains buried until pedogenesis “welds” the overlying sediment to the buried solum. Complete welding is accomplished when no observable material, interpreted taxonomically as a C horizon, is present between the buried and burying profiles. A special type of buried soil, the isolated paleosol, is not currently affected by surface pedogenic processes. The lower limit of these surficial processes is called the depth of isolation. All isolated paleosols are buried below this depth, which varies depending upon local conditions. We present a theoretical model that uses paleosol characteristics to predict the depth of isolation. Data from 29 buried and exhumed paleosols in Kansas suggest that isolated paleosols do exist, although at greater depths than orginally anticipated.

Because pedoturbation processes (soil mixing) occur in all soils in varying degrees during the curse of their evolution, mixing processes should be assessed within the larger context of soil genesis. Soils may be viewed as evolving along two pedogenic pathways that operate concurrently: a progressive pathway that includes processes, factors, and conditions that promote ordered, differentiated and/or deep profiles; and a regressive pathway that promotes disordered, simplified, rejuvenated, and/or shallow profiles. Pedoturbative processes that disrupt, blend, destroy, or prevent the formation of horizons, subhorizons, or genetic layers, such that simplified profiles evolve from more ordered ones, are proisotropicand function within the regressive pathway. Pedoturbative processes that form or aid in the formation and maintenance of horizons, subhorizons, or genetic layers and/or promote increased profile order are proanisotropicand function within the progressive pathway.