Limit of the Upper Confining Unit of the Gray Limestone Aquifer, Southwestern Florida, USGS WRIR 99-4213, fig. 21

The upper confining unit of the gray limestone aqifer in southwestern Florida ranges from 20 to 60 ft in thickness in most of the study area, but is absent to the west and southwest in much of Collier County and most of Monroe County. The upper confining unit exists east of the line in the data set, with two small circular areas depicting areas where the unit is absent (to the north) and present (to the south). The unit is also present to the southwest of the short line in the southwest part of the area. The map shows the limit of the upper confining unit of the gray limestone aquifer in Collier, Hendry, Miami-Dade, and Monroe counties.

The purpose of this report is to evaluate the hydrogeologic framework, hydraulic properties, and ground-water flow of the gray limestone aquifer in southern Florida. The report also emphasizes the geologic framework (stratigraphy and structure) and the hydrogeologic framework (aquifers and confining and semiconfining units) above and below the gray limestone aquifer.