STRATIGRAPHIC RECONNAISSANCE OF THE BUSH BAY FORMATION, ENGADINE GROUP, HIAWATHA NATIONAL FOREST, UPPER PENINSULA, MI

Within the Upper Peninsula of Michigan lies the Hiawatha National Forest and the poorly understood, yet complex, Engadine Group. This mid-Silurian unit is directly situated above the Manistique Group and below the Salina Group. It is comprised of three formations of dolostone differing in composition and depositional environment. An attempt to better understand this group has been made over the past several years through field and lab work. The upper-most unit, the Bush Bay Formation, is the focus of this study. The Bush Bay Formation has a negligible dip and has a maximum thickness of 20m. For this reason, a stratigraphic section of the Bush Bay Formation was measured by walking up a slope over a distance of roughly 1.2 kilometers, gaining about 15m of elevation within the Pontchartrain Shores area, east of St. Ignace, MI. An auto-level and stadia rod were used to measure the formation along the shallow slope representing the paleo-lakeshore of glacial Lake Nipissing (ca. 7.5ka). Twenty hand samples were collected along with measurements for distance and elevation of the slope. The sampled outcrops were comprised of slope breaks, reef mounds, grike fields, and alvar. Hand sample analysis was conducted and showed a general increase in styolites going up section as well as variances in texture. Moldic porosity with infilling was consistent among the majority of samples and there was a general increase of identifiable fossils going up section (stromatoporids, corals, brachiopods, and crinoids). Standard petrographic thin section analysis will be conducted on the samples collected to identify microscopic scale changes in stratigraphy of the Bush Bay Formation.