The Citronelle Formation in Alabama is composed mainly of coarse sand with thin, sporadic clay lenses. The clay lenses locally give rise to perchea water tables and springs. The recent occurrence of structural damage due to the localized subsidence of the Citronelle Formation has led to the discovery of in situ transformation of kaolinite to gibbsite due to groundwater leaching. The gibbsite is euhedral, associated with quartz and kaolinite. Spectra taken from surface coatings on quartz grains indicate the presence of alumina, suggesting the presence of an amorphous, precursor of the gibbsite. It appears that the intermediate, amorphous compound is required for the redistribution of alumina in the sediment. This phenomenon is as sporadic as the occurrence of clay lenses and springs in the Citronelle Formation. The leaching is more pronounced in the vicinity of springs due to maintenance of aqueous silica undersaturation with respect to the gibbsitekaolinite transformation reaction. Kinetic data given by Lasaga (1984) and mass transfer calculations indicate that the transformation can occur rapidly in the telogenetic zone if gibbsite precipitation is effective.