ABSTRACT: The Late Ordovician (Katian; Richmondian) Waynesville Formation is an important unit for its juxtaposition relative to a series or paleoecological events. The Waynesville Formation includes the Richmondian Invasion and records a critical part of the transitional period between the Great Ordovician Biodiversification Event and the end Ordovician Hirnantian Extinction. The Waynesville can be correlated across the Cincinnati Arch through the use of epibole taxa and long-term invaders, including the brachiopods Glyptorthis insculpta, Catazyga headi, and Eochonetes clarksvillensis, and colonial and solitary corals. This paper subdivides theWaynesville Formation into twelve beds and submembers, which are discussed herein, with respect to lithology, sequence stratigraphic position, and paleontology, with special attention to occurrences of new or distinctive taxa. In addition, a refined, high resolution stratigraphic framework highlights the brief timing of a major phase of the Richmondian Invasion associated with the base of the Clarksville Member and herein termed the â€œClarksville Phaseâ€. This study thus establishes a high-resolution stratigraphic framework within which to gage the timing and facies context of physical and biotic dynamics during an important interval of ecological turnover.