Hydrostratigraphic Groupings of the Craton within CONUS-Extents and Outcrops

The U.S. Geological Survey (USGS) is developing a National Extent Hydrogeologic Framework (NEHF) for the conterminous United States (CONUS). This digital data set is one of several conceptually linked data releases that provide the underlying spatial data that underpin the development of the NEHF. Three of the datasets describe the thickness and spatial extent of lower Paleozoic rocks (Sharpe and others, 2026a), upper Paleozoic and Triassic and Jurassic rocks (Sharpe and others, 2026b), and Cretaceous rocks (Sharpe and Belitz, 2026). In a fourth data release, CONUS was divided into eight hydrogeologic provinces (Kauffman and Belitz, 2025). This data release focuses on mapping the outcrop areas and buried extents of hydrostratigraphic groupings (HGs), which consist of strata with a shared range of geologic age and broadly comparable hydrogeologic characteristics. The HGs are mapped in two of the provinces: the Central Interior province and the Colorado Plateau and Laramide Rocky Mountain Basins province. Together, these two provinces correspond to the cratonic interior of CONUS. The NEHF conceptualizes the hydrogeologic framework of the cratonic interior as a vertically stacked sequence of HGs. From top to bottom (youngest to oldest), the HGs are identified as: 1. Quaternary-Tertiary-Cretaceous (QTK) 2. Intermediate Cretaceous (Intmd-K) 3. Lowermost Cretaceous (LK) 4. Jurassic-Triassic (JT) 5. Permian-Pennsylvanian (PP) 6. Older Paleozoics, comprised of the Cambrian, Ordovician, Silurian, Devonian, and Mississippian Periods (COSDM) Each of the HGs consists of a sequence of previously mapped time-stratigraphic units (Sharpe and others, 2026a; Sharpe and others, 2026b; Sharpe and Belitz, 2026). With the exception of Cretaceous strata, the time-stratigraphic units correspond to geologic Periods. Time-stratigraphic units of Cretaceous age generally correspond to geologic Epochs. The lateral extent of the strata of a given Period or Epoch is documented in the companion data releases. The lateral extents of the time-stratigraphic units were aggregated for each of the HGs to define the lateral extent of the HG. One objective of the NEHF is to understand the hydrogeologic connections amongst these HGs. To facilitate comparison and analysis, within the extent of each HG, the areas where the HG is outcropping – exposed at land surface – or overlain by other HGs, called the buried extent, are identified. In addition, within the areas mapped as buried extent, the presence or absence of overlying unconsolidated Pleistocene deposits from "Laurentide" or "Cordilleran" glaciation are identified (USGS, 2003). The outcrop areas and buried extents for each of the six HGs are released as separate shapefiles that essentially “stack” in 2D map space. The buried extents and outcrop areas for each of the six HGs are released as separate shapefiles in a compressed (zip) file named Hydrostratigraphic_Groupings_Craton_Shapefiles.zip. Citations: Kauffman, L.J., and Belitz, K., 2025, Hydrogeologic provinces of the conterminous United States: U. S. Geological Survey data release, https://doi.org/10.5066/P13Z6EQR. Sharpe, J.B., Belitz, K., Fleming, B.J., and Donmoyer, S.J., 2026a, Digital representation of isopach maps for selected geologic periods from an atlas published by Sloss and others (1960) (ver. 2.0, July 2026): U.S. Geological Survey data release, https://doi.org/10.5066/P1GFQCQX. Sharpe, J.B., Belitz, K., Smout, B., and Watson, E., 2026b, Digital representation of selected isopach and geologic maps from U.S. Geological Survey paleotectonic publications (ver. 2.0, July 2026): U.S. Geological Survey data release, https://doi.org/10.5066/P9NEQQFY. Sharpe, J.B., and Belitz, K., 2026, Digital Representation of Isopach Maps for Selected Sequences of the Cretaceous Published by Reeside (1944) and Other Sources (ver. 2.0, July 2026): U.S. Geological Survey data release, https://doi.org/10.5066/P13VYIIZ. U.S. Geological Survey, 2003, Principal Aquifers of the 48 Conterminous United States, Hawaii, Puerto Rico, and the U.S. Virgin Islands: U.S. Geological Survey data release, https://doi.org/10.5066/P9Y2HOUJ.

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