| Abstract: | 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 Ca(58.7)Mg(41.3). Dolomites of this chemical composition are typical of the supratidal environment. However, the dolomite has isotopic composition delta0(18) = 5.8 per mille, deltaC(13) = 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. |
