Grits and conglomerates intercalated in the argillaceous material of the Etruria marls (Carboniferous) of north Staffordshire, England, contain clastic fragments in a chamosite- carbonate cement, which is sometimes manganiferous. Contrary to the conclusion that Carboniferous basic rocks have contributed to the formation of the marls, it is shown that the constituent fragments probably derived from pre-Cambrian and Cambrian rocks.

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