A DETAILED PETROLOGICAL INVESTIGATION OF THE BYRON FORMATION PERI-TIDAL MARINE LIMESTONES AND DOLOSTONES, MICHIGAN BASIN, USA

The Byron Fm. is well dated in the Michigan Basin to the middle Aeronian Stage (Llandovery Series - Silurian Period). The unit, which is part of the Burnt Bluff Group (BBG), is comprised of alternating muddy limestones and dolostones interpreted to reflect deposition in a peri-tidal marine setting. Stratigraphically, the Byron Fm. lies above the open marine limestones of the older Lime Island Fm. and below the reefal limestones of the younger Hendricks Fm. Previous petrographic observations suggest that dolomitization occurred very early, and may have been driven by evaporative fluids in a tidal influenced setting. The current study aims to test this model of dolomitization by integrating newly acquired petrological data collected from a series of representative and well-preserved limestone-dolomite packages in the Brown Snowplow 1-5 core (Alpena Co., Michigan). The data presented will include thin section and scanning electron microscope (SEM) petrography, detailed powder x-ray diffraction (XRD) mineralogy, bulk rock x-ray fluorescence (XRF) and micrometer-scale SEM-energy dispersive spectroscopy (SEM-EDS) elemental analyses, and stable isotope (δ¹⁸O, δ¹³C) geochemistry.