Hydrogeology, Ground-Water Movement, and Subsurface Storage in the Floridan Aquifer System in Southern Florida. Regional Aquifer-System Analysis

摘要

The Floridan aquifer system of southern Florida is composed chiefly of carbonate rocks that range in age from early Miocene to Paleocene. The top of the aquifer system in southern Florida generally is at depths ranging from 500 to 1,000 feet, and the average thickness is about 3,000 feet. The Upper Floridan aquifer contains brackish ground water, and the Lower Floridan aquifer contains salty ground water that compares chemically to modern seawater. Ground-water movement in the Upper Floridan aquifer is generally southward from the area of highest head in central Florida, eastward to the Straits of Florida, and westward to the Gulf of Mexico. Ground-water movement in the Lower Floridan aquifer is inland from the Straits of Florida. The concentration gradients of the carbon and uranium isotopes indicate that the source of cold saltwater in the Lower Floridan aquifer is seawater that has entered through the karst features on the submarine Miami Terrace near Fort Lauderdale. The results of the study support the hypothesis of circulating relatively modern seawater and cast doubt on the theory that the saltwater in the Floridan aquifer system probably is connate or unflushed seawater from high stands of sea level.