BIOSTRATIGRAPHIC ANALYSIS OF A MCKAY BAY MEMBER (BUSH BAY FORMATION) MID-SILURIAN KNOLL REEF IN MICHIGAN’S UPPER PENINSULA

This study focuses on a dolomitized mid-Silurian knoll reef located in Michigan’s Hiawatha National Forest at the eastern end of Michigan’s Upper Peninsula. These dolomitized reefs are stratigraphically located in the McKay Bay Member, in the Bush Bay Formation, of the Engadine Group. Throughout the 1960s and 1970s previous efforts conducted visual investigations of the knoll reef blocks to help identify reef distributions throughout the Michigan Basin. However, to this day features have remained only partially described based on hand sample analysis. This study was designed to further investigate the knoll reefs using a Gigapan Epic Pro to collect photogrammetric high-resolution images and petrographic analysis of thin sections to create and analyze the reefs biostratigraphy analysis.

The knoll reef in this study measures 24 meters by 25 meters and reaches 5.5 meters in height. Samples of the reef were collected for petrographic analysis every 5 meters in four transverse sampling surveys. Horizontal and vertical thin sections of samples collected of the well-preserved stromatolites and stromatoporoids were made to determine if remnants of other marine organisms are identifiable. This study will attempt to describe one of the knoll reefs found within the forest and create a bio stratigraphic map of the reef itself.