INVESTIGATING BRACHIOPOD PYRITIZATION UNDER LABORATORY CONDITIONS

Pyrite (FeS₂) is a well-known iron ore found in strata with coal and shale. It is also known to replace minerals in fossils through the process of pyritization. This study attempts to replicate the pyritization of marine brachiopod fossils under experimental conditions. Brachiopods were buried in various sediments with controlled quantities of Fe₂O₃ and H₂SO₄, as well as plants and sediment acquired at the pond on campus as a source of sulfur-reducing bacteria. Preliminary experiments with jars built up too much pressure to contain and seal the experiment without them blowing their tops. A second experiment was rigged in much the same way as a wine air lock system, for comparison to the first. The second experiment was set up in larger bottles but had the same amount of reactants as the jars. Results from the first 50 days are mixed, and a longer deployment period is planned. After 58 days the control was opened and it was opened and it revealed that the brachiopods leave molds in the form of bubbles in their shape as long as they are buried under sediment. SEM imaging of residue leaking from one of the jars in the first experimental run revealed microscopic crystals with a morphology consistent with pyrite. Reaction of calcite with sulfuric acid produced significant amounts of gypsum, but visible crystals of pyrite were not evident at this time.