Drilling Core (image) Max-Planck-Gesellschaft Share Print E-Mail Caption This shows a light yellow lamina of dolomite within dark mud of siliceous algae (diatoms). Such dolomite layers, which may contain also barite and enrichments of archaeol, indicate the depths of ancient sulphate-methane transition zones. Credit MPI for Marine Microbiology Usage Restrictions None Share Print E-Mail Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.