This data set represents the extent of the Silurian Devonian aquifers in the states of Michigan, Wisconsin, Illinois, Indiana, Ohio, Kentucky, and Tennessee.

This data set represents the extent of the Silurian Devonian aquifers in the states of Michigan, Wisconsin, Illinois, Indiana, Ohio, Kentucky, and Tennessee.

This geodatabase includes spatial datasets that represent the Mississippian aquifer in the States of Alabama, Illinois, Indiana, Iowa, Kentucky, Maryland, Missouri, Ohio, Pennsylvania, Tennessee, Virginia and West Virginia. The aquifer is divided into three subareas, based on the data availability. In subarea 1 (SA1), which is the aquifer extent in Iowa, data exist of the aquifer top altitude and aquifer thickness. In subarea 2 (SA2), which is the aquifer extent in Missouri, data exist of the aquifer top and bottom aquifer surface altitudes. In subarea 3 (SA3), which is the aquifer area of the remaining States, no altitude or thickness data exist. Included in this geodatabase are: (1) a feature dataset "ds40MSSPPI_altitude_and_thickness_contours that includes aquifer altitude and thickness contours used to generate the surface rasters for SA1 and SA2, (2) a feature dataset "ds40MSSPPI_extents" that includes a polygon dataset that represents the subarea extents, a polygon dataset that represents the combined overall aquifer extent, and a polygon dataset of the Ft. Dodge Fault and Manson Anomaly, (3) raster datasets that represent the altitude of the top and the bottom of the aquifer in SA1 and SA2, and (4) georeferenced images of the figures that were digitized to create the aquifer top- and bottom-altitude contours or aquifer thickness contours for SA1 and SA2. The images and digitized contours are supplied for reference. The extent of the Mississippian aquifer for all subareas was produced from the digital version of the HA-730 Mississippian aquifer extent, (USGS HA-730). For the two Subareas with vertical-surface information, SA1 and SA2, data were retrieved from the sources as described below. 1. The aquifer-altitude contours for the top and the aquifer-thickness contours for the top-to-bottom thickness of SA1 were received in digital format from the Iowa Geologic Survey. The URL for the top was ftp://ftp.igsb.uiowa.edu/GIS_Library/IA_State/Hydrologic/Ground_Waters/ Mississippian_aquifer/mississippian_topography.zip. The URL for the thickness was ftp://ftp.igsb.uiowa.edu/GIS_Library/IA_State/Hydrologic/Ground_Waters/ Mississippian_aquifer/mississippian_isopach.zip Reference for the top map is Altitude and Configuration, in feet above mean sea level, of the Mississipian Aquifer modified from a scanned image of Map 1, Sheet 1, Miscellaneous Map Series 3, Mississippian Aquifer of Iowa by P.J. Horick and W.L. Steinhilber, Iowa Geological Survey, 1973; IGS MMS-3, Map 1, Sheet 1 Reference for the thickness map is Distribution and isopach thickness, in feet, of the Mississipian Aquifer, modified from a scanned image of Map 1, Sheet 2, Miscellaneous Map Series 3, Mississippian Aquifer of Iowa by P.J. Horick and W.L. Steinhilber, Iowa Geological Survey, 1973; IGS MMS-3, Map 1, Sheet 2 2. The altitude contours for the top and bottom of SA2 were digitized from georeferenced figures of altitude contours in U.S. Geological Survey Professional Paper 1305 (USGS PP1305), figure 6 (for the top surface) and figure 9 (for the bottom surface). The altitude contours for SA1 and SA2 were interpolated into surface rasters within a GIS using tools that create hydrologically correct surfaces from contour data, derive the altitude from the thickness (depth from the land surface), and merge the subareas into a single surface. The primary tool was an enhanced version of "Topo to Raster" used in ArcGIS, ArcMap, Esri 2014. ArcGIS Desktop: Release 10.2 Redlands, CA: Environmental Systems Research Institute. The raster surfaces were corrected in areas where the altitude of the top of the aquifer exceeded the land surface, and where the bottom of an aquifer exceeded the altitude of the corrected top of the aquifer.

This geodatabase includes spatial datasets that represent the Mississippian aquifer in the States of Alabama, Illinois, Indiana, Iowa, Kentucky, Maryland, Missouri, Ohio, Pennsylvania, Tennessee, Virginia and West Virginia. The aquifer is divided into three subareas, based on the data availability. In subarea 1 (SA1), which is the aquifer extent in Iowa, data exist of the aquifer top altitude and aquifer thickness. In subarea 2 (SA2), which is the aquifer extent in Missouri, data exist of the aquifer top and bottom aquifer surface altitudes. In subarea 3 (SA3), which is the aquifer area of the remaining States, no altitude or thickness data exist. Included in this geodatabase are: (1) a feature dataset "ds40MSSPPI_altitude_and_thickness_contours that includes aquifer altitude and thickness contours used to generate the surface rasters for SA1 and SA2, (2) a feature dataset "ds40MSSPPI_extents" that includes a polygon dataset that represents the subarea extents, a polygon dataset that represents the combined overall aquifer extent, and a polygon dataset of the Ft. Dodge Fault and Manson Anomaly, (3) raster datasets that represent the altitude of the top and the bottom of the aquifer in SA1 and SA2, and (4) georeferenced images of the figures that were digitized to create the aquifer top- and bottom-altitude contours or aquifer thickness contours for SA1 and SA2. The images and digitized contours are supplied for reference. The extent of the Mississippian aquifer for all subareas was produced from the digital version of the HA-730 Mississippian aquifer extent, (USGS HA-730). For the two Subareas with vertical-surface information, SA1 and SA2, data were retrieved from the sources as described below. 1. The aquifer-altitude contours for the top and the aquifer-thickness contours for the top-to-bottom thickness of SA1 were received in digital format from the Iowa Geologic Survey. The URL for the top was ftp://ftp.igsb.uiowa.edu/GIS_Library/IA_State/Hydrologic/Ground_Waters/ Mississippian_aquifer/mississippian_topography.zip. The URL for the thickness was ftp://ftp.igsb.uiowa.edu/GIS_Library/IA_State/Hydrologic/Ground_Waters/ Mississippian_aquifer/mississippian_isopach.zip Reference for the top map is Altitude and Configuration, in feet above mean sea level, of the Mississipian Aquifer modified from a scanned image of Map 1, Sheet 1, Miscellaneous Map Series 3, Mississippian Aquifer of Iowa by P.J. Horick and W.L. Steinhilber, Iowa Geological Survey, 1973; IGS MMS-3, Map 1, Sheet 1 Reference for the thickness map is Distribution and isopach thickness, in feet, of the Mississipian Aquifer, modified from a scanned image of Map 1, Sheet 2, Miscellaneous Map Series 3, Mississippian Aquifer of Iowa by P.J. Horick and W.L. Steinhilber, Iowa Geological Survey, 1973; IGS MMS-3, Map 1, Sheet 2 2. The altitude contours for the top and bottom of SA2 were digitized from georeferenced figures of altitude contours in U.S. Geological Survey Professional Paper 1305 (USGS PP1305), figure 6 (for the top surface) and figure 9 (for the bottom surface). The altitude contours for SA1 and SA2 were interpolated into surface rasters within a GIS using tools that create hydrologically correct surfaces from contour data, derive the altitude from the thickness (depth from the land surface), and merge the subareas into a single surface. The primary tool was an enhanced version of "Topo to Raster" used in ArcGIS, ArcMap, Esri 2014. ArcGIS Desktop: Release 10.2 Redlands, CA: Environmental Systems Research Institute. The raster surfaces were corrected in areas where the altitude of the top of the aquifer exceeded the land surface, and where the bottom of an aquifer exceeded the altitude of the corrected top of the aquifer.

This geodatabase includes spatial datasets that represent the Cambrian-Ordovician aquifer system in the States of Wisconsin, Michigan, Minnesota, Iowa, and Illinois. Included are: (1) a polygon dataset that represents the aquifer system extent, (2) raster datasets for the altitude of each aquifer subunit, (3) altitude, or if applicable, thickness contours used to generate the surface rasters, (4) georeferenced images of the figures that were digitized to create the altitude or thickness contours, (5) the line datasets representing the altitude contours that were digitized from the images, and (6) an ArcGIS Toolbox used to develop the surface raster datasets. The images and digitized contours are supplied for reference. The extent of the Cambrian-Ordovician aquifer system is from the linework of the Cambrian-Ordovician aquifer system extent maps in U.S. Geological Survey Professional Paper 1405-B (PP1405B), and a digital version of the aquifer extent presented in the Groundwater Atlas of the United States (the U.S. Geological Survey Hydrologic Atlas 730-J, (USGS HA 730-J) and 730-K (USGS HA 730-K)), available at http://water.usgs.gov/ogw/NatlAqCode-reflist.html . The Cambrian-Ordovician Aquifer System has four aquifer subunits, in order from the most surficial to the deepest: (A1) St. Peter Sandstone Aquifer, (A2) Prairie du Chien Aquifer, (A3) Ironton and Galesville Sandstone Aquifer, and (A4) Mt. Simon or Lamotte Sandstone Aquifer. The altitude contour line datasets for each subunit available were digitized from georeferenced figures of altitude contours in PP1405B, and the altitude values were interpolated into surface rasters within a GIS using tools that create hydrologically correct surfaces from contour data, derives the altitude from the thickness (depth from the land surface), and merges the subareas into a single surface. The primary tool was "Topo to Raster" used in ArcGIS, ArcMap, Esri 2014. (ArcGIS Desktop: Release 10.2 Redlands, CA: Environmental Systems Research Institute). The surface rasters were corrected for the areas where the altitude of the top of the aquifer exceeded the land surface, and where the bottom of an aquifer exceeded the altitude of the corrected top of the aquifer.

This geodatabase includes spatial datasets that represent the Cambrian-Ordovician aquifer system in the States of Wisconsin, Michigan, Minnesota, Iowa, and Illinois. Included are: (1) a polygon dataset that represents the aquifer system extent, (2) raster datasets for the altitude of each aquifer subunit, (3) altitude, or if applicable, thickness contours used to generate the surface rasters, (4) georeferenced images of the figures that were digitized to create the altitude or thickness contours, (5) the line datasets representing the altitude contours that were digitized from the images, and (6) an ArcGIS Toolbox used to develop the surface raster datasets. The images and digitized contours are supplied for reference. The extent of the Cambrian-Ordovician aquifer system is from the linework of the Cambrian-Ordovician aquifer system extent maps in U.S. Geological Survey Professional Paper 1405-B (PP1405B), and a digital version of the aquifer extent presented in the Groundwater Atlas of the United States (the U.S. Geological Survey Hydrologic Atlas 730-J, (USGS HA 730-J) and 730-K (USGS HA 730-K)), available at http://water.usgs.gov/ogw/NatlAqCode-reflist.html . The Cambrian-Ordovician Aquifer System has four aquifer subunits, in order from the most surficial to the deepest: (A1) St. Peter Sandstone Aquifer, (A2) Prairie du Chien Aquifer, (A3) Ironton and Galesville Sandstone Aquifer, and (A4) Mt. Simon or Lamotte Sandstone Aquifer. The altitude contour line datasets for each subunit available were digitized from georeferenced figures of altitude contours in PP1405B, and the altitude values were interpolated into surface rasters within a GIS using tools that create hydrologically correct surfaces from contour data, derives the altitude from the thickness (depth from the land surface), and merges the subareas into a single surface. The primary tool was "Topo to Raster" used in ArcGIS, ArcMap, Esri 2014. (ArcGIS Desktop: Release 10.2 Redlands, CA: Environmental Systems Research Institute). The surface rasters were corrected for the areas where the altitude of the top of the aquifer exceeded the land surface, and where the bottom of an aquifer exceeded the altitude of the corrected top of the aquifer.

This geodatabase includes spatial datasets which represent the Lower Cretaceous aquifer system in the States of Iowa, Kansas, Minnesota, Montana, Nebraska, North Dakota, South Dakota, and Wyoming. Included are: (1) a polygon dataset that represents the aquifer system extent, (2) raster datasets for the altitude of each aquifer subarea, (3) altitude and thickness contours (plus thickness fault lines) used to generate the surface rasters, (4) georeferenced images of the figures that were digitized to create the altitude and thickness contours. The images and digitized contours are supplied for reference. The extent of the Lower Cretaceous aquifer for all subareas was produced from the linework of the Lower Cretaceous aquifers maps in U.S. Geological Survey Professional Paper 1414-E (USGS PP 1414-E) Plate 6, U.S. Geological Survey Water-Resources Investigations Report 84-4153 (USGS WRIR 84-4153) Plate 1, and the U.S. Geological Survey Hydrologic Atlas 730 (USGS HA-730). A digital version of the HA-730 Lower Cretaceous aquifer extent is presented in the Groundwater Atlas of the United States (the U.S. Geological Survey Hydrologic Atlas 730-D,(USGS HA 730-D), 730-I (USGS HA 730-I), and 730-J (USGS HA 730-J. The Lower Cretaceous Aquifer System has 4 aquifer subareas: (SA1) Great Plains aquifer, (SA2) Iowa aquifer, (SA3) Minnesota aquifer, and (SA4) Northern Great Plains aquifer. The altitude lines for the top of SA1 and SA4 were digitized from georeferenced figures of altitude contours in USGS PP 1414-E Plate 4 and USGS PP 1402-B Plate 1. Altitude lines for the top of SA3 were digitized from WRIR 84-4153 Figure 5. The top of SA2 was derived from the thickness contours for SA2, USGS PP 1414-E Figure 16. Areas of overlap between subareas were deleted, based on available original data. The altitude values and thickness values were interpolated into surface rasters within a GIS using tools that create hydrologically correct surfaces from contour data, derives the altitude from the thickness (depth from the land surface), and merge the subareas into a single surface. The primary tool was "Topo to Raster" used in ArcGIS, ArcMap, Esri 2014. The raster surfaces were corrected for the areas where the altitude of the top of the aquifer exceeded the land surface, and where the bottom of an aquifer exceeded the altitude of the corrected top of the aquifer. For a more detailed description of the processes used by the data compiler, please see the Supplementary Information section.

This geodatabase includes spatial datasets which represent the Lower Cretaceous aquifer system in the States of Iowa, Kansas, Minnesota, Montana, Nebraska, North Dakota, South Dakota, and Wyoming. Included are: (1) a polygon dataset that represents the aquifer system extent, (2) raster datasets for the altitude of each aquifer subarea, (3) altitude and thickness contours (plus thickness fault lines) used to generate the surface rasters, (4) georeferenced images of the figures that were digitized to create the altitude and thickness contours. The images and digitized contours are supplied for reference. The extent of the Lower Cretaceous aquifer for all subareas was produced from the linework of the Lower Cretaceous aquifers maps in U.S. Geological Survey Professional Paper 1414-E (USGS PP 1414-E) Plate 6, U.S. Geological Survey Water-Resources Investigations Report 84-4153 (USGS WRIR 84-4153) Plate 1, and the U.S. Geological Survey Hydrologic Atlas 730 (USGS HA-730). A digital version of the HA-730 Lower Cretaceous aquifer extent is presented in the Groundwater Atlas of the United States (the U.S. Geological Survey Hydrologic Atlas 730-D,(USGS HA 730-D), 730-I (USGS HA 730-I), and 730-J (USGS HA 730-J. The Lower Cretaceous Aquifer System has 4 aquifer subareas: (SA1) Great Plains aquifer, (SA2) Iowa aquifer, (SA3) Minnesota aquifer, and (SA4) Northern Great Plains aquifer. The altitude lines for the top of SA1 and SA4 were digitized from georeferenced figures of altitude contours in USGS PP 1414-E Plate 4 and USGS PP 1402-B Plate 1. Altitude lines for the top of SA3 were digitized from WRIR 84-4153 Figure 5. The top of SA2 was derived from the thickness contours for SA2, USGS PP 1414-E Figure 16. Areas of overlap between subareas were deleted, based on available original data. The altitude values and thickness values were interpolated into surface rasters within a GIS using tools that create hydrologically correct surfaces from contour data, derives the altitude from the thickness (depth from the land surface), and merge the subareas into a single surface. The primary tool was "Topo to Raster" used in ArcGIS, ArcMap, Esri 2014. The raster surfaces were corrected for the areas where the altitude of the top of the aquifer exceeded the land surface, and where the bottom of an aquifer exceeded the altitude of the corrected top of the aquifer. For a more detailed description of the processes used by the data compiler, please see the Supplementary Information section.

This geodatabase includes spatial datasets that represent the Texas Coastal Uplands and Mississippi Embayment aquifer system in the States of Alabama, Arkansas, Illinois, Kentucky, Louisiana, Mississippi, Missouri, Tennessee, and Texas. Included are: (1) polygon extents; datasets that represent the aquifer system extent, the entire extent subdivided into subareas or subunits, and any polygon extents of special interest (outcrop areas, no data available, areas underlying other aquifers, anomalies, for example), (2) raster datasets for the altitude of each aquifer subarea or subunit, (3) altitude, and/or if applicable, thickness contours used to generate the surface rasters, (4) georeferenced images of the figures that were digitized to create the altitude and thickness contours. The images and digitized contours are supplied for reference. The extent of the Texas Coastal Uplands and Mississippi Embayment aquifer system is derived from the linework in the aquifer system extent maps in U.S. Geological Survey Professional Paper 1416-B (USGS PP 1416-B), plates 11, 13, 15, 16, and 17, and from a digital version of the aquifer extents presented in the U.S. Geological Survey Hydrologic Atlas 730, Chapters E and F. The Texas Coastal Uplands and Mississippi Embayment aquifer system has 6 aquifer subunits, in order from the most surficial to the deepest: A1: Upper Claiborne aquifer, A2: Middle Claiborne aquifer, A3: Lower Claiborne- Upper Wilcox aquifer, A4: Middle Wilcox aquifer, A5: Lower Wilcox aquifer, A6: McNairy-Nacatoch aquifer. The altitude and thickness contours for each available subunit were digitized from georeferenced figures of altitude contours in USGS PP 1416-B, and the resultant top and bottom altitude values were interpolated into surface rasters within a GIS using tools that create hydrologically correct surfaces from contour data, derives the altitude from the thickness (depth from the land surface), and merges the subareas into a single surface. The primary tool was an enhanced version of "Topo to Raster" used in ArcGIS, ArcMap, Esri 2014. The raster surfaces were corrected for the areas where the altitude of an underlying layer of the aquifer exceeded altitude of an overlying layer.

This geodatabase includes spatial datasets that represent the Southeastern Coastal Plain aquifer system in the States of Alabama, Georgia, Mississippi, South Carolina, and Tennessee. Included are: (1) polygon extents; datasets that represent the aquifer system extent, the entire extent subdivided into subareas or subunits, and any polygon extents of special interest (outcrop areas, no data available, areas underlying other aquifers, anomalies, for example), (2) raster datasets for the altitude of each aquifer subarea or subunit, (3) altitude, and/or if applicable, thickness contours used to generate the surface rasters, (4) georeferenced images of the figures that were digitized to create the altitude and thickness contours. The images and digitized contours are supplied for reference. The extent of the Southeastern Coastal Plain aquifer system is derived the linework in the Southeastern Coastal Plain aquifer system extent maps in a digital version of the aquifer extent presented in the Groundwater Atlas of the United States (the U.S. Geological Survey Hydrologic Atlas HA-730-F, -730-G, and -730-K. The Southeastern Coastal Plain aquifer system has 4 aquifer subunits, in order from the most surficial to the deepest: A1: Chickasawhay River aquifer, A2: Pearl River Aquifer, A3: Chattahoochee River Aquifer, and A4: Black Warrior River Aquifer. The altitude and thickness contours for each available subunit were digitized from georeferenced figures of altitude contours in U.S. Geological Survey Profession Paper 1410-B, (USGS PP 1410-B), and the resultant top and bottom altitude values were interpolated into surface rasters within a GIS using tools that create hydrologically correct surfaces from contour data, derive the altitude from the thickness (depth from the land surface), and merge the subareas into a single surface. The primary tool was "Topo to Raster" used in ArcGIS, ArcMap, Esri 2014. The surface rasters were corrected for the areas where the altitude of an underlying layer of the aquifer exceeded altitude of an overlying layer.