Cooperative National Geologic Map: Quaternary geology

The USGS National Cooperative Geologic Mapping Program (NCGMP) was directed by Congress to create a new geologic map of the United States” by “bring[ing] together detailed national and continental-resolution 2D and 3D information produced throughout the Survey and by federal and state partners” (House Report 116-100). To fulfill this goal, the NCGMP created a map synthesis engine (Johnstone and others, 2025) based on the Geologic Map Schema (GeMS) standard (NCGMP, 2020) and used it to bring together source geologic maps originally published by the USGS and State Geological Surveys. This thematic map layer was derived from this database using procedures described by Johnstone and others (2025) and is intended to serve as a legible national map of the nation; while it retains full descriptions of geologic units from source materials it does not include the full search functionality (described in Johnstone and others, 2025) that is facilitated by a true relational database.
The Quaternary Geology layer depicts Quaternary geologic units exposed at the earth’s surface over the entire conterminous United States, inclusive of everything from glacial deposits to lava flows. This includes all units that may, or are known to, span the Quaternary – Neogene boundary. Where present, units older than Quaternary and map units that are primarily colluvium and/or residuum are categorized as generalized rock and regolith units. In the glaciated regions of the Midwest and Northeast, the map is a composite of 8 state geologic maps depicting Quaternary deposits. In the West and parts of the Southeast, the map is a composite of Quaternary units from 19 state geologic maps depicting geology at the earth’s surface. The remaining area is populated from 18 regional Quaternary geologic maps produced as part of the USGS Quaternary Atlas series. The map is structured as a single GeMS database with three additional tables (also described in Johnstone and others, 2025); a Source_DescriptionOfMapunits table preserves all source inputs, a synthesis_to_source_units table relates aggregated national units to original map units, and a Symbol_Lookup table provides definitions of all FGDC geologic map symbol code values (U.S. Geological Survey, 2006) used for stylizing the map.