Stratigraphic Controls on Distribution of Hydraulic Conductivity in Carbonate Aquifers

Purpose and Scope: The objective of this project was to characterize the hydraulic conductivity distribution of carbonate aquifers in the Silurian (Niagaran) and Ordovician (Sinnipee) dolomites in eastern Wisconsin (Figure 1) by integrating sequence stratigraphy with geophysical and hydrogeologic data. The integration of methodologies and approaches from reservoir geology and hydrogeology has led to a better understanding of the controls on the distribution of hydraulic conductivity in carbonate rocks. Specific objectives varied for the different aquifers. More hydrogeologic data were available for the Silurian (Sherrill, 1978; Bradbury and Muldoon, 1992; Gianniny and others, 1996; Muldoon and Bradbury, 1998; Bradbury and others, 1998); for this aquifer the objective was to further refine the sequence stratigraphic framework and determine its relationship with previously mapped high-permeability zones and hydrostratigraphic units. Relatively few data were available on the hydraulic conductivity of the Sinnipee, however, the sequence stratigraphic framework was well developed (Simo and others, 1995; Choi, 1995). For the Sinnipee, the specific objectives were to 1) define hydrostratigraphic units in the Fox River Valley and other parts of eastern Wisconsin where it is the uppermost bedrock unit and 2) determine if these zones could be correlated on a regional scale. In addition to the above, specific objectives applicable to both aquifers included: 1) construction of cross-sections illustrating hydrostratigraphic units, stratigraphic discontinuities, and discrete high-permeability zones; 2) correlation of high-permeability zones with stratigraphic discontinuities/zones; and 3) compilation of databases of hydraulic conductivity values for both the Silurian and Sinnipee dolomites that can be used by individuals and agencies interested in groundwater flow and transport in fractured carbonates.