Marine Dolomite of Unusual Isotopic Composition

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Science  13 Jan 1967:
Vol. 155, Issue 3759, pp. 189-191
DOI: 10.1126/science.155.3759.189-a


A piston core taken off of the coast of Oregon in 358 meters of water contained an indurated calcareous layer composed partly of dolomite with a composition Ca58.7Mg41.3. Dolomites of this chemical composition are typical of the supratidal environment. However, the dolomite has isotopic composition δ018 = 5.8 per mille, δC13 = 35.1 per mille relative to the Chicago PDB-I standard. The unusual carbon isotope ratio is similar to that of calcites produced as a byproduct of bacterial breakdown of hydrocarbons.