CHAPTER 11: CONNEAUT GROUP TO BASAL MISSISSIPPIAN STRATIGRAPHIC SUCCESSION AND GEOCHRONOLOGY, NEW YORK/PENNSYLVANIA BORDERLAND AND LAKE ERIE REGION

We review strata and geochronological events between the Late Famennian Conneaut Group (Palmatolepis marginifera Zone) and the Devonian-Mississippian boundary (base of Protognathodus kockeli Zone) in New York, Pennsylvania, and Ohio. Lower divisions include offshore marine to paralic deposits in the Conneaut and Conewango groups in New York and correlative Chadakoin and Venango formations in northwest Pennsylvania, as well as strata comprising parts of the Chagrin Member of the Ohio Shale in Ohio. Nonmarine deposits coeval to the Conneaut and Conewango groups, are largely represented by red Catskill magnafacies in New York and Pennsylvania.

Marine-to-paralic units in the post-Conewango–pre-Mississippian time slice in Ohio include, in ascending order, the Cleveland Member of the Ohio Shale, the Bedford Shale, and the Berea Sandstone. In northwest Pennsylvania they include the provisional “Drake Well formation”, Oswayo and Knapp formations, and Corry Sandstone as well as newly erected Berea-equivalent divisions. Coeval nonmarine deposits in Pennsylvania are represented by largely non-red lower portions of the Huntley Mountain Formation and by the diamictite-bearing Spechty Kopf Formation. The Mississippian commences with transgressive dark shale deposits of the Cuyahoga succession in Ohio and Pennsylvania.

The post-Conewango time slice was dominated by major oscillations in climate that include the global Dasberg Event and Hangenberg Biocrisis interval with associated major changes in sea level during the latest Devonian. In Ohio, the Dasberg transgression was marked by the overspread of basinal black shale facies recorded by the Cleveland Shale Member. The later Hangenberg Biocrisis interval appears to be within the topmost Cleveland Shale-into-Berea succession, though biozonal control is poor. The aftermath of the initial Hangenberg Biocrisis is recorded by unusual, sparsely fossiliferous deposits of the Bedford and Berea formations. The major disconformity below the Cussewago Sandstone-Berea Sandstone succession across Pennsylvania and Ohio, appears to be a glacial signal, possibly linked to Spechty Kopf diamictites. A current challenge is to establish better biostratigraphical control in central Ohio where the end-Devonian section is more nearly continuous.