Inherited vs. acquired complexity in east Texas weathering profiles

Complexity in weathering profiles may reflect variability in the parent material and/or complex feedback relationships within regolith weathering systems. Because regolith formation modifies or destroys the parent material, it is difficult to determine the extent to which variability in the weathering profile is inherited, as opposed to created by the weathering processes. The state probability function (SPF), designed to model the spatial pattern of transitions in system states, is applied to complex weathering profiles formed in glauconitic materials in east Texas to address this issue. The weathering profile is remarkably complex, with units ranging from unweathered parent material to highly modified weathering products similar to those found in the Bt horizons of the overlying Rhodic Paleudalf. There is a very general vertical sequence with more weathered material near the top and less weathered material near the bottom; however, the pattern is quite irregular. Highly weathered units are found everywhere except at the base of the study section, and much less developed units are found throughout. Though the SPF indicates a high degree of spatial complexity, the value never approaches or exceeds that which would be expected in a random vertical sequence of weathering horizons. Variation inherited from the parent material would produce SPF values greater than that for a random sequence. The complex patterns in the east Texas regolith are thus attributable primarily to feedbacks within the weathering system and indicate that the complexity is dominantly acquired. Whatever anisotropy there may have been in the parent material has been magnified and overprinted by complex interactions within the weathering system.