IMPLICATIONS FOR DETAILED GEOLOGIC MAPPING ON THE AGGREGATE INDUSTRY IN IOWA

The Iowa Geological Survey (IGS) has been participating in the U.S. Geological Survey (USGS) National Cooperative Geologic Mapping Program called STATEMAP since its inception in 1993. For the last several years the IGS has taken a paired mapping approach, producing surficial and bedrock geologic maps for each mapping area. The bedrock maps are aimed at improving upon the existing statewide bedrock geologic map that was published in 2010 at 1:500,000 scale. Naturally, mapping at that scale meant lumping formations together or simply using groups as mapping units. Recent mapping projects in north-central and south-eastern Iowa have focused on Devonian and Mississippian sequences that could reasonably be mapped at the formation level. The process of mapping at 1:100,000 or 1:24,000 scale allows for refinement of the geologic data in a given mapping area. Although the final product is a map, the ancillary benefits to the mapping program are improved data point locations, refined bedrock topography (from 50’ to 25’ contour intervals), enhanced resolution of erosional outliers, and improved understanding of the stratigraphy of formations and members. These maps provide a much more intricate illustration of the complex geology that the statewide map simply could not attain.

Detailed mapping has opened the door to many opportunities to provide valuable geologic information to the citizens and industries that depend on Iowa’s vast and varied geologic resources. The IGS is poised to build upon the refined geologic framework produced under the STATEMAP program by generating derivative maps suited to the needs of our users. Detailed geologic mapping may be the key to finding and protecting future aggregate resources.