GIS staff at the Wisconsin Geological and Natural History Survey constructed a preliminary 4-county 3-D lithologic model of Crawford, Monroe, Richland, and Vernon Counties. The model was constructed from data that had been refined for several WGNHS projects.
Over the last decade, WGNHS staff geocoded WDNR Well Construction Reports (WCRs) from digital and analog sources. In a GIS, the points representing water well boreholes were inspected, edited, and assigned a location confidence. Next, the land surface elevation for each well was extracted from a DEM. The land surface elevation was then used to “hang” each well’s downhole lithology. By displaying and exaggerating the data in ESRI ArcScene, the different lithologies were selected and classified into a very general stratigraphy. Structural surfaces for each lithologic unit’s base elevation were interpolated and inspected to identify outliers in the point data. After many rounds of editing, all obvious outliers had been edited or removed.
The relief of the preliminary topography of the lithologic contacts reveal that there is relief on the on all of underlying bedrock units. The relief of these rock layers may be influencing, if not guiding, the flow of water at and below the land surface. The topography of the lithologic units may be influencing long-term erosion.
A simplified lithologic model constructed from well records using ESRI ArcGIS is only one of the steps to creating a geologic map. Geologic maps can inform decision making about land use and land practices, land conservation, zoning, planning, and the construction & engineering of roads. WGNHS personnel will continue to add and interpret new information into our current 3-D lithologic data.
