Isotope geochemistry of the Miocene and Quaternary carbonate rocks in Rabigh area, Red Sea coast, Saudi Arabia

The oxygen and carbon isotopic composition of the Miocene and Quaternary carbonate rocks in Rabigh area show a broad range of δ13C and δ18O. The Quaternary carbonate rocks have significantly higher δ13C than the Miocene ones, but low δ13C values of the Miocene samples likely indicate a high contribution of carbon from organic sources at the time of deposition. Linear trends are evident in both groups of samples supporting the likelihood of secondary alteration.