The geochemistry and mineralogy of the Permian red beds of Southwest England

Detailed mineralogical and chemical examination of some hundred rock samples representing the Permian red bed sequence of Southwest England has been carried out. Mineral—element correlations are presented and factor analysis of the chemical data shows that 80% of the variance can be explained by seven factors. Among these are recognised a clay factor; detrital minerals versus carbonate factor; halide and sulphate factors and a volcanic enrichment factor. The behaviour of elements in the strong oxidising environment associated with red bed deposition is discussed. In particular, zirconium is shown to be enriched in red bed clays, reflecting solution from the source area. Cerium, in its oxidised state as Ce⁴⁺ is shown to be strongly correlated with the carbonate phase, indicating its tendency to form relatively stable carbonate complexes. Strontium is positively correlated with the clays and negatively correlated with carbonate, while sulphur (as SO₄^2?) is associated with carbonate usually in the form of barytes. The origin of the red pigment is also discussed.