PALEOECOLOGICAL AND PALEOENVIRONMENTAL ANALYSIS OF THE MIDDLE DEVONIAN DUNDEE FORMATION AT WHITEHOUSE, LUCAS COUNTY, OHIO

Middle Devonian faunas from the eastern United States have been well-studied for over a century. Many analyses have been done on units of the Appalachian Basin (e.g., Columbus Limestone in Ohio and Onondaga Limestone in New York) and Michigan Basin (Silica Shale Formation in Ohio). However, the Early Middle Devonian Dundee Formation of the Michigan Basin has never been studied in detail. This project provides paleontological and lithological data in order to interpret the paleoecology and paleoenvironment for the Dundee Formation. In particular, a comparison of community composition between the Dundee and time-equivalent Appalachian Basin carbonates and the slightly younger, siliciclastic Silica Shale was performed.

The Dundee Limestone is well-exposed at the Whitehouse Quarry in Lucas County, Ohio. Hand samples and thin sections tied to five measured sections from the quarry provide a context for interpreting both lithological and paleontological data. The unit shows a shallowing-upward trend through typical shallow subtidal carbonate wackestones and packstones, with storm deposits becoming more frequent towards the top of the exposed section. Much of the Dundee Formation appears to have been bioturbated, with Thalassinoides-type burrows most common. The top of the section shows a pronounced change from nodular and wavy-bedded tempestites to harder, more massive, bluer beds with large colonial rugose and tabulate corals and stromatoporoids. This colonial coral assemblage resembles that from the Columbus Limestone exposed at Marblehead Quarry, Ottawa County, Ohio.

Nineteen 40 cm x 40 cm rock slab samples were taken from eight stratigraphic horizons at the Whitehouse, Ohio quarry. Fossil taxa found within a 20 cm x 20 cm grid randomly placed on the slab were identified and counted. Dominant taxa include brachiopods, tentaculitids, and rugose corals; fish bones are common in some horizons. Substantial species-level overlap exists in the fauna, both through the Dundee itself and between the Dundee and overlying Silica Shale Formation. Linkages between the Michigan and Appalachian Basins are also evident.