Estimation of Precambrian basement topography in Central and Southeastern Wisconsin from 3D modeling of gravity and aeromagnetic data

• Three dimensional geophysical modeling improved resolution from previous work.
• Detailed basement topography in Fond Du Lac County and southeastern Wisconsin.
• Better subsurface geologic structure for developing conceptual hydrogeologic models.

Increased concerns about groundwater resources in Wisconsin have brought about the need for better understanding of the subsurface geologic structure that leads to developing conceptual hydrogeologic models for numerical simulation of groundwater flow. Models are often based on sparse data from well logs usually located large distances apart and limited in depth. Model assumptions based on limited spatial data typically require simplification that may add uncertainty to the simulation results and the accuracy of a groundwater model. Three dimensional (3D) modeling of gravity and aeromagnetic data provides another tool for the groundwater modeler to better constrain the conceptual model of a hydrogeologic system. The area near the Waukesha Fault in southeastern Wisconsin provides an excellent research opportunity for our proposed approach because of the strong gravity and aeromagnetic anomalies associated with the fault, the apparent complexity in fault geometry, and uncertainty in Precambrian basement depth and structure. Fond du Lac County provides another opportunity to apply this approach because the Precambrian basement topography throughout the area is known to be very undulated and this uneven basement surface controls water well yields and creates zones of stagnant water. The results of the 3D modeling of gravity and aeromagnetic data provide a detailed estimation of the Precambrian basement topography in Fond Du Lac County and southeastern Wisconsin that may be useful in determining ground water flow and quality in this region.