Several Middle Devonian formations in the Michigan Basin are potential targets for geological sequestration of CO₂, including the Dundee Limestone and the Rogers City Limestone. The Rogers City and Dundee limestones are disparate carbonate formations but are typically combined in subsurface nomenclature as the Dundee Limestone because they are difficult to differentiate in some areas. In much of the basin, however, the Rogers City and Dundee can be differentiated using wireline logs. Subdivision of the two formations was first accomplished in outcrop and is also straightforward in core on the basis of starkly different lithologic properties. Subsurface subdivision is especially important for reservoir characterization and/or geological sequestration studies because the Rogers City and Dundee differ in lithology, thickness, and reservoir properties. Regional geological sequestration capacity estimates for the undifferentiated Dundee Limestone obscure the relative contributions of the Rogers City and Dundee and oversimplify known geological heterogeneity. When evaluated separately using wireline logs supported by limited conventional core studies and porosity and permeability data, the Rogers City is clearly demonstrated to be only a local sequestration target with an estimated geological sequestration capacity of 0.13 Gt. In contrast, storage capacity in the Dundee is estimated at 1.88 Gt. This analysis indicates that the Dundee is a more laterally extensive, regional sequestration target compared to the Rogers City. Individual geological sequestration capacity estimates for the Rogers City and Dundee reflect differences in reservoir properties for the two units and are therefore more geologically defensible than estimates for the undifferentiated Dundee Limestone.