Geodatabase of the available top and bottom surface datasets that represent the Mississippian aquifer, Alabama, Illinois, Indiana, Iowa, Kentucky, Maryland, Missouri, Ohio, Pennsylvania, Tennessee, Virginia and West Virginia

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.

Tags: aquifer, aquifer-system, extent, groundwater, inlandwaters, iowa, mississippian-aquifer, northern-missouri, united-states, usgs-f1ebfddd-3fe2-48d4-9c46-0bbbc0c9198c
Organization: Department of the Interior