Marine Diagenesis of Shallow Marine Lime-Mud Sediments: Insights from δO18 and δC13 Data

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Science  13 Sep 1968:
Vol. 161, Issue 3846, pp. 1130-1132
DOI: 10.1126/science.161.3846.1130


Shallow marine lime-mud sediments of the Ste. Genevieve Formation (Mississippian), in part of the Illinois Basin, underwent at least three diagenetic changes: (i) local dolomitization in seawater or a brine, producing dolostone having average δC13 of +2.5 per mille and δO18 of +1.9 per mille (versus PDB-1); (ii) more usually cementation of unreplaced CaCO3, in intrasediment seawater, yielding isotopically marine lime mudstone mainly composed of calcite, 4-micron or finer, with δO18 of from -1 to +1 per mille; (iii) later partial alteration of CaCO3, in permeable dolomitic rocks, by isotopically "lighter" waters, to calcite with an estimated δO18 of -10 per mille or less. Isotope data appraised by petrographic analysis thus suggest "submarine" cementation of these carbonates in shallow marine conditions.

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