Abstract

Isotope analyses distinguish biogenic sulfur deposits from nonbiogenic deposits but do not distinguish bioepigenetic from biosyngenetic deposits. Sulfur deposits in cap rocks over salt domes and in bedded Permian evaporites of West Texas, however, are clearly bioepigenetic. Anhydrite, introduced by salt diapirs into geologically younger sediments, is converted biogenically to sulfur and calcite in the presence of petroleum in cap rock over the Challenger Knoll, a salt dome at a water depth of 12,000 ft in the Gulf of Mexico. Bedded evaporites of West Texas in association with petroleum show an obvious epigenetic displacement of the anhydrite layers by biogenic sulfur and calcite.

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