BIOSTRATIGRAPHIC ANALYSIS OF TABULATE AND RUGOSA CORAL FOUND IN A MCKAY BAY MEMBER KNOLL REEF UPPER PENINSULA, MICHIGAN

This project is a preliminary investigation of the coral fossil assemblage of an early-Silurian-aged dolomitized knoll reef. The reef is stratigraphically located in the McKay Bay Member, in the Bush Bay Formation, of the Engadine Group. The knoll reef is found in the Hiawatha National Forest at the eastern end of Michigan’s Upper Peninsula. Knoll reefs are carbonate mounds that form in shallow waters, which hamper the reefs ability to grow vertically, forcing the reef to grow horizontally instead. Due to this low-energy environment, knoll reefs are primarily composed of mud and carbonate grains.

Dolomitization of the reef caused many of the fossils to be lost and left with moldic voids. Over 100 hand samples and cores were collected at 1-meter intervals across a reef. The samples were collected in a transected grid pattern every 22.5 degrees and are being analyzed through petrographic analysis. Multiple examples of rugosa and tabulate coral megafossils were also identified in situ. This study attempts to identify specific coral species and document their spatial locations within the reef to better understand the paleoenvironment at the time of their deposition.