The thickness contours were created using biostratigraphic data in the Paleo-Data, Inc., Tenroc Regional Geologic Database. The depths of the microfossil locations were associated with the wells data provided by the Louisiana Department of Natural Resources. Because of the proprietary nature of the Tenroc database, no actual data can be shown and only those data points contained in the Louisiana State wells database are included in the control points layer. Contouring was accomplished in Dynamic Graphics, Inc., EarthVision modeling software (v.5) using minimum tension gridding. Three custom programs were used to convert contour lines generated from grids in EarthVision to Arc/Info coverages and then to shapefiles. The data are provided as both lines and polygons (mmthicklg.shp and mmthickpg.shp), and the public wells that penetrate the entire thickness of the Middle Miocene sequence are provided in a point shapefile (mmthickptg.shp). These datasets contain basic data and interpretations developed and compiled by the U.S. Geological Survey's Framework Studies and Assessment of the Gulf Coast Project. Other major sources of data include publicly available information from state agencies as well as publications of the U.S. Geological Survey and other scientific organizations. In cases where company proprietary data were used to produce various derivatives such as contour surfaces, the source is cited but the data are not displayed.