Chemical and clay mineralogical properties of Memphis, Grenada, Calloway and Henry series were determined and related to degree of internal drainage and genesis. Percent base saturation and other chemical data indicated that the more poorly drained profiles were more severely leached than better drained members. These data, together with the occurrence of larger proportions of expanding lattice 2:1 type minerals to nonexpanding 2:1 types in the more poorly drained profiles, suggest that a high degree of weathering was attained before pan horizon formation occurred. The presence of lower exchangeable Ca/Mg + Na ratios along with lower montmorillonite/vermiculite ratios in B 3m horizons than in deeper or shallower horizons suggests that the pans are the result of packing of dispersed clay particles and that vermiculite has formed from montmorillonite or other weathering products in those horizons.
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Hutcheson et al. (1959) studied this question.