Abstract

Petrographic study of a vertebrate-bearing cannel coal which underlies the Upper Freeport coal (late Westphalian D, Upper Carboniferous) in the area of Linton, Ohio, provides information on the depositional conditions represented by fossiliferous sapropelic coals. Samples of the cannel obtained from an approximately 10-km-long curvilinear area were prepared as polished blocks and point counted in reflected light. The cannel typically consists of over 50 percent very finely grained, micrinite-rich groundmass; approximately 25 percent exinite and 10 percent pyrite; and varying amounts of vitrinite and inertinite. Sporinite is the most abundant exinite, but no alginite occurs; euhedra and framboids are the most common forms of pyrite; and vitrinite is poorly preserved and virtually structureless. Vertebrate scales, teeth, and bones preserved in the cannel show no significant mineralogic alteration. These petrographic findings agree with results from an investigation of the physical paleoenvironment of the Linton deposit, and together these data sets indicate that the vertebrate-bearing cannel represents a freshwater sapropelic peat that formed within abandoned segments of a fluviodeltaic channel. In the absence of clastic influx, macerated plant debris and resistant spores accumulated in the bottom of the channel, and decay of these organic-rich sediments led to anaerobic conditions in which sulfate-reducing bacteria thrived. Vertebrate remains introduced from the overlying oxygenated waters were not subjected to scavenging in this anoxic, nonacidic setting but slowly rotted, leaving skeletal parts intact.

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