AGE RELATIONS OF THE MIDDLE DEVONIAN LIMESTONES IN OHIO

The long continued practice of correlating the Middle Devonian limestones on the east and west flanks of the Cincinnati arch in Ohio has been questioned by more recent workers. This doubt has arisen partly because of a better under-standing of stratigraphic relationships with rocks of similar age in adjoining states, partly on a more detailed knowledge of the lithologic conditions, but mainly be-cause of a better understanding of the fossils within the formations. The "Columbus " limestone of northwestern Ohio west of the anticline is recog-nized now as a continuation southward of the Dundee limestone of the southern peninsula of Michigan, and the approximate age of the Delaware limestone east of the anticline in Ohio and southwestern Ontario. It is therefore younger than the Columbus limestone which lies below the Delaware limestone in these latter regions. The purpose of this paper is to bring together data already known on these Devonian limestones in this State, and to add further information, particularly on the faunas, which might help to underwrite existing opinions on the subject