Inherited vs. acquired complexity in east Texas weathering profiles

Complexity in weathering profiles may reflect variability in the parent mat erial and/or complex feedback relationships within regolith weathering syst ems. Because regolith formation modifies or destroys the parent material, i t is difficult to determine the extent to which variability in the weatheri ng profile is inherited, as opposed to created by the weathering processes. The state probability function (SPR 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 we athering profile is remarkably complex, with units ranging from unweathered parent material to highly modified weathering products similar to those fo und in the Bt horizons of the overlying Rhodic Paleudalf. There is a very g eneral vertical sequence with more weathered material near the top and less weathered material near the bottom; however, the pattern is quite irregula r. Highly weathered units are found everywhere except at the base of the st udy section, and much less developed units are found throughout. Though the SPF indicates a high degree of spatial complexity, the value never approac hes or exceeds that which would be expected in a random vertical sequence o f weathering horizons. Variation inherited from the parent material would p roduce SPF values greater than that for a random sequence. The complex patt erns in the east Texas regolith are thus attributable primarily to feedback s within the weathering system and indicate that the complexity is dominant ly acquired. Whatever anisotropy there may have been in the parent material has been magnified and overprinted by complex interactions within the weat hering system. (C) 2001 Elsevier Science B.V. All rights reserved.