The Floridan aquifer system, composed of the Upper and Lower Floridan aquifers, is a thick sequence of Paleogene carbonate rock which spans an area of about in the southeastern United States, it underlies parts of which  state in the southern region of the United States, with part of its southern border formed by the Gulf of Mexico, and its western border is formed by the Mississippi River?
Mississippi Mississippi is a state in the southern region of the United States, with part of its southern border formed by the Gulf of Mexico. Its western border is formed by the Mississippi River.
Geography of South Dakota South Dakota is a state located in the north-central United States. It is usually considered to be in the Midwestern region of the country. The state can generally be divided into three geographic regions: eastern South Dakota, western South Dakota, and the Black Hills. Eastern South Dakota is lower in elevation and higher in precipitation than the western part of the state, and the Black Hills are a low, isolated mountain group in the southwestern corner of the state. Smaller sub-regions in the state include the Coteau des Prairies, Coteau du Missouri, James River Valley, the Dissected Till Plains, and the Badlands. Geologic formations in South Dakota range in age from two billion-year-old Precambrian granite in the Black Hills to glacial till deposited over the last few million years. South Dakota is the 17th-largest state in the country.