18O and 34S in the Upper Bartonian gypsum deposits of the Paris basin

Isotopic analyses (¹⁸O and ³⁴S) of the Eocene gypsum from the Paris basin show a range beyond the normal Tertiary marine values. The possibility of a reduction process during diagenesis is discussed.A hypothesis of continental origin by leaching of Permotriassic deposits is proposed for this formation on the basis of a comparison of the isotopic contents recorded from Germany and eastern France.