USING MAGNETIC SUSCEPTIBILTY AND STABLE ISOTOPES TO CORRELATE OUTCROPS OF THE ENGADINE GROUP WITHIN THE HIAWATHA NATIONAL FOREST OF THE UPPER PENINSULA, MI

Samples were collected from various locations around the Hiawatha National Forest, Upper Peninsula Michigan to refine the stratigraphic framework of the Engadine Group of the middle Silurian. Overall, there is a lack of research in this area, especially differentiating these dolostone outcroppings. A total of 48 samples were collected from two quarries, three boulder fields, two exposures of the Niagara Escarpment, and three outcroppings. Samples were analyzed for magnetic susceptibility and stable oxygen and carbon isotopes to determine if there is a stratigraphic correlation between sites exists using these parameters. In hand sample, some of these dolostones had significant iron oxides within fractures and pores. Within Scott’s Quarry, magnetic susceptibility is inversely related to the total weight percentage of Fe₂O₃ determined by geochemical analysis; higher magnetic susceptibility correspond to lower Fe₂O₃ percentages. In addition, the relationship between magnetic susceptibility and total weight percent impurities show a similar trend as the iron oxide weight percentage. Changes in magnetic susceptibility can correlate with changes in sedimentary provenance and geochemistry, providing a potential tool for outcrop differentiation and correlation. In addition to the susceptibility data, carbon and oxygen stable isotopes were used to correlate and differentiate stratigraphy. Previous investigations of the Engadine Group in Wisconsin identified an increase of δ¹³C in the early Engadine followed by a period of oscillating values between +2 and +4 per mil. Collectively, these data will be used in conjunction with petrographic, mineralogical, and geochemical data in order to place the outcroppings and boulder fields within the Hiawatha National Forest into their proper stratigraphic framework.