Detailed chemical and isotopic studies of mineralization of septarian fractures in concretions in the Devonian Marcellus Shale document a complicated paragenesis involving multiple episodes of metal-carbonate precipitation during methane fermentation. It is proposed (1) that a first period of methane fermentation occurred during burial and diagenesis in the Devonian, (2) that a second period occurred as strontium-bearing Silurian brines were displaced upward near the toe of Pleistocene glaciation, and (3) that witherite replaced barite during sulfate reduction and another period of methane fermentation in a Pleistocene mixture of reducing conditions below thick ice cover. Fluid-inclusion data, oxygen-isotope values of carbonate minerals, and strontium-isotope ratios are all consistent with these suggestions.
|Number of pages
|Bulletin of the Geological Society of America
|Published - Jan 1 1987
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