This datafile shows the general elevation of the top of the New Albany Shale.����These 20- and/or 100-foot isolines were contoured using Esri ArcGIS software.����The contours were created using over data points from the ISGS Oracle database.����The data covers only those portions of the state where the formation is present and does not include any coverage outside of Illinois where the formation may be present.����This data set is intended for use at a scale of 1:100,000 or greater.����These data are appropriate for use in local and regional thematic analysis.�� The data are not appropriate as a geodetic, legal or engineering base.