Student Scholars Day

Glauconite and Pyrite in Chert Nodules and Dolomite in the Silurian Brassfield Formation of Northern Kentucky

Henry Hall Atrium 26

The Silurian Brassfield Formation in northern Kentucky is comprised of dolomite, with local concentrations of chert nodules. The formation originated as a coral reef that was dolomitized following lithification to limestone. Glauconite and pyrite can be found in small amounts throughout the limestone and chert nodules. Plain light microscopy of dolomite and chert samples was used to determine the association of glauconite with pyrite, and reflected light microscopy was utilized to determine the pyrite morphology. If framboidal morphology of the pyrite is observed, this may indicate that the pyrite formed in an environment in which bacteria reduced sulfate to sulfide resulting in the formation of pyrite. Glauconite may have also formed in association with the pyrite. Moreover, removing the sulfate may result in conditions conducive to formation of organogenic dolomite, which could then form the nucleation sites for further dolomitization.