A NATIONAL-RESOLUTION COMPILATION OF QUATERNARY GEOLOGY FOR THE CONTERMINOUS UNITED STATES

Many geologic maps of the conterminous United States, including the Geologic Map of North America (Reed et al., 2005) and the Geologic map of the United States (King and Beikman, 1974) exclude the Quaternary deposits that are immediately underfoot for millions of Americans. The US Geological Survey National Cooperative Geologic Mapping Program (NCGMP) decadal strategic plan (Brock et al., 2021) calls for the creation of an integrated 2D and 3D geologic-framework model by 2030. Here we present efforts by the USGS National Geologic Synthesis project to produce a map of Quaternary geology across the conterminous US, a product that will ultimately compliment similar layers depicting older geology. Our approach to synthesis is driven by the incorporation of published geologic mapping, where we seek to preserve source content and assign common queryable attributes to existing maps rather than reinterpret those maps. For a first version, Quaternary geologic mapping was sourced from the U.S. Geological Survey Quaternary Atlas series (1:1,000,000 scale) and state geologic maps (generally around 1:500,000). We integrate the description of map units from each of the ~70 maps based on a suite of standard descriptive attributes while also preserving original narrative descriptions. Original narrative descriptions provide nuanced and holistic characterizations of units and the opportunity for advanced analysis via natural language processing, while integrated attributes streamline the process of making national-scale queries and derivative products. With thousands of unique original units, a simplified set of compilation map units are essential for legible visualizations. We assign compilation map units by leveraging taxonomies we establish for vocabularies that define descriptive attributes assigned to each original map unit. We therefore expect that this approach is scalable and readily updatable; allowing us to incorporate new maps to produce incremental revisions. Using a focus area spanning the Rocky Mountains and Great Plains we demonstrate how this strategy can be used to efficiently produce a map compilation, generate derivative map products, and highlight and characterize discrepancies between neighboring maps that could be iteratively resolved to produce a coherent depiction of the nation’s geology.