Stable oxygen and carbon isotope studies were performed on unionid shells from Rhine and Meuse rivers. Results show that the characteristic isotopic signature of each river is well documented in the shells with average δ18O values of ∼9.00‰ for the Rhine specimens and of 6.5‰ for the Meuse unionid. The average δ18O values of the shell material corresponds to the average δ18O of the to rivers and thus identifies Rhine or Meuse sedimentary sequences. All δ18O records show distinct seasonality, which may be used to reconstruct past riverconditions
