Isotopic composition of Cretaceous shallow-water carbonates from DSDP Site 384.

Abstract

125 m of shallow water carbonates were drilled. It was evident by the presence of moldic porosity that at least part of this material had been exposed to meteoric water. Pre-existing aragonite of skeletal particles had been leached and the resulting vugs were in some cases partly filled with sparry low-Mg calcite cement. Since the isotopic composition of marine- and fresh-water carbonates is considerably different a difference might also be expected between the fresh-water diagenetic carbonates and the unaltered overlying pelagic nannofossil chalk. Stable isotope analysis was used to substantiate the suggested diagentic history of these carbonates. -Authors