Correlation of the subsurface Lower and Middle Devonian of the Lake Erie region
The completion of 6 detailed cross sections using the gamma-ray logs of 94 closely spaced wells has provided new correlations and confirmed some earlier correlations of the Lower and Middle Devonian strata of the Lake Erie region. These sections connect western New York; northwestern Pennsylvania; northern, central, and northwestern Ohio; southwestern Ontario; and southeastern Michigan. The Lower Devonian Bois Blanc Limestone of western New York is continuous with the type Bois Blanc of northern Michigan via southwestern Ontario. It has been traced southwestward across northern Ohio and southward into the lower part of the type Columbus Limestone in central Ohio. The Edgecliff, Clarence, Nedrow, and Moorehouse Members of the overlying Middle Devonian Onondaga Limestone of western New York correlate with the Upper Columbus Limestone of Ohio; the Seneca Member of the Onondaga is equivalent to the overlying Delaware Limestone. The Amherstburg and Lucas Formations of the Detroit River Group of Michigan and Ontario can be traced southward across Lake Erie into the lower and middle parts of the Upper Columbus of Ohio. The Amherstburg correlates with the Edgecliff, Clarence, Nedrow, and lower Moorehouse Members of the New York Onondaga; the Lucas correlates with the middle part of the Moorehouse Member. The Dundee Limestone of northwestern Ohio, Michigan, and Ontario is an equivalent of the upper Moorehouse and Seneca Members of the New York Onondaga Limestone. It is not coterminous with the Delaware of Ohio, as the base of the Dundee is significantly older than the base of the Delaware. These correlations have been strengthened by tracing the stratigraphic positions of four different ash beds through the upper part of the carbonate sequence; three of these ash beds are parts of the type Tioga Ash Bed in the subsurface of northern Pennsylvania. A major, regional unconformity separates the Lower and Middle Devonian carbonate sequence from the overlying Middle Devonian terrigenous one; the Delaware and Dundee Limestones cannot be correlated with any part of the Marcellus Formation of the New York Hamilton Group. In western New York, the Cherry Valley Limestone Member of the Marcellus Formation rests directly and unconformably upon the Onondaga. In northwestern Pennsylvania and northeastern Ohio, the Union Springs Shale reappears between the Cherry Valley and the Onondaga. Beneath central Lake Erie, the Union Springs, Cherry Valley, and Oatka Creek Members of the Marcellus merge into the Bell Shale, Rockport Quarry Limestone, and Arkona Shale of Ontario. The Arkona can be traced across Lake Erie into the Plum Brook and Lower Olentangy Shales of Ohio. The lower part of the terrigenous sequence of the Lake Erie region consequently is Marcellus in age, not Skaneateles. The Prout (Ohio) and Hungry Hollow (Ontario) Limestones are homotaxial and correlate with the Centerfield Limestone of New York. The Rockport Quarry, Arkona, and Hungry Hollow can be traced into the Silica Shale of southeastern Michigan and northwestern Ohio. The Widder Shale and Ipperwash Limestone of Ontario merge into the Tenmile Creek Dolomite of Michigan and Ohio.