THE RELATION BETWEEN THE TERRA ROSSA AND THE CARBONATE-FREE RESIDUE OF THE

A statistical comparison has been made of chemical data for terra rossa and carbonate-free residues of Cretaceous limestones and dolostones in Apulia in order to evaluate the hypothesis that the terra rossa is a product of weathering of the underlying carbonate rocks. It has been shown that the differences in chemical composition between the residue of the carbonate rocks and the terra rossa are consistent with the former being the parent material of the latter, The transformation from carbonate rock residue to terra rossa was governed mainly by chemical weathering which produced a marked decrease in the K20/AI203 (i.e. illite/kaolinite) ratio. The geochemical pattern of the Apulian terra rossa has been influenced by sedimentary processes which have led to a characteristic distribution of mineralogical components and a moderate contamination by biogenic silica.