A PALEOENVIRONMENTAL ANALYSIS OF THE MIDDLE DEVONIAN GRAVEL POINT FORMATION, WESTERN MICHIGAN
A paleoenvironmental analysis of the Gravel Point Formation, a stromatoporoid patch reef deposit exposed in western Michigan, provides insights into conditions existing in the Michigan Basin during the Middle Devonian Period (Givetian). Samples were collected from shore cliffs and bedding planes at six locations along the Lake Michigan coastline of Little Traverse Bay. The six sample locations yielded an invertebrate fauna consisting of 19 species, distributed among brachiopods, corals, bryozoans, arthropods, cephalopods, stromatoporoids, ostracodes, and polychaets, as well as a possible arthropod fragment. The palynologic component consists primarily of amorphous organic matter, followed by algal colonies, scolecodonts, miospores, and acritarchs. This is the first report of ostracodes and polychaets within the Gravel Point Formation. The fossil assemblage, along with sedimentologic evidence, indicates the Gravel Point Formation was deposited in a low energy, shallow, normal marine environment, with intermittent storm episodes.