CONTINENTAL-SCALE INVESTIGATIONS USING A NATIONAL GEOLOGIC MAP DATABASE: FIRST STEPS TOWARDS A NATIONAL SYNTHESIS OF QUATERNARY GEOLOGIC MAPS

The Quaternary geologic history of the U.S. is cataloged in thousands of geologic maps produced over many decades. However, the disparate nature of these individual maps makes it challenging to assess resources, address problems in Quaternary geology, or systematically characterize natural hazards at a national scale. The National Geologic Synthesis (NGS) project is working to change that. Following a congressional mandate to “bring together detailed national and continental-resolution 2D and 3D information produced throughout the Survey and by federal and state partners,” NGS is working to produce new digital geologic maps of the nation at multiple resolutions by 2030. Here we demonstrate the first steps towards a living representation of Quaternary geology at continental scales. Quaternary geologic mapping was sourced from the Quaternary Atlas series (1:1,000,000 scale) and state geologic maps (1:500,000 – 1:750,000) compiled in the State Geologic Map Compilation (Horton et al., 2017). Each dataset was modernized to be compatible with the Geologic Map Schema standard (U.S. Geological Survey National Cooperative Geologic Mapping Program, 2020). Original descriptions of units from each of the around 50 maps and an integrated set of descriptive attributes are saved in related tables. Original narrative descriptions provide nuanced 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 well over a thousand original units, neither of those approaches alone produce a visually readable map. Rather than make a priori assignments we programmatically assign compilation map units, assemble a hierarchy, and summarize compilation unit attributes based on a customizable set of rules for how to differentiate map units. This rule-based strategy for building compilation units allows for different derivative maps to be easily generated from the primary database, producing a visually legible synthesis of the nation’s Quaternary geology that can be configured for different needs. Here we showcase how this strategy can be used to efficiently produce different thematic maps and iteratively evolve toward a seamless map of the nation.