Question: 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?
Context: 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. The Ogallala Aquifer is a shallow water table aquifer surrounded by sand, silt, clay and gravel located beneath the Great Plains in the United States.  One of the world's largest aquifers, it underlies an area of approximately 174000 sqmi in portions of eight states (South Dakota, Nebraska, Wyoming, Colorado, Kansas, Oklahoma, New Mexico, and Texas).  It was named in 1898 by geologist N. H. Darton from its type locality near the town of Ogallala, Nebraska.  The aquifer is part of the High Plains Aquifer System, and rests on the Ogallala Formation, which is the principal geologic unit underlying 80% of the High Plains. A Sole Source Aquifer (SSA) is an aquifer that has been designated by the United States Environmental Protection Agency (EPA) as the sole or principal source of drinking water for an area.  By definition, SSA is an aquifer that supplies at least 50% of the drinking water consumed in the area overlying the aquifer.  There may be other factors to designate SSA.  For example, in New York City, Kings and Queens Counties are designated as SSA not because the aquifer of these areas are the sole or principal sources of drinking water for these counties; they are designated as SSA because the geographic boundaries of Kings and Queens Counties are within the recharge zone for the aquifers underlying the southeastern Surficial aquifers are shallow aquifers typically less than 50 ft thick, but larger surficial aquifers of about 60 ft have been mapped.  They mostly consist of unconsolidated sand enclosed by layers of limestone, sandstone or clay and the water is commonly extracted for urban use.  The aquifers are replenished by streams and from precipitation and can vary in volume considerably as the water table fluctuates.  Being shallow,they are liable to contamination by fuel spills, industrial discharge, landfills, and saltwater.  Parts of southeastern United States are dependent on surficial aquifers for their water supplies. The Southern Hills aquifer system is the primary source of public water in the northern ten parishes of southeastern Louisiana.  The aquifer dips towards the Gulf of Mexico and extends from the northern limit of the recharge region near Vicksburg, Mississippi, and as far south as the Baton Rouge area in south Louisiana.  There are about thirteen aquifer units composing the system in the southern part of the area.  The water is primarily a soft, sodium bicarbonate type with an dissolved-solids concentration of about 220 milligrams per liter in southern Louisiana. 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 the entire state of Florida and parts of Alabama, Georgia, Mississippi, and South Carolina. The Madison Limestone is a thick sequence of mostly carbonate rocks of Mississippian age in the Rocky Mountain and Great Plains areas of western United States.  The rocks serve as an important aquifer as well as an oil reservoir in places.  The Madison and its equivalent strata extend from the Black Hills of western South Dakota to western Montana and eastern Idaho, and from the Canada–United States border to western Colorado and the Grand Canyon of Arizona. Gerhardminnebron is a natural karst spring located a few kilometers east of Ventersdorp in South Africa and draining into the Wonderfonteinspruit and Mooi River, which in turn flows into the Vaal River.  It yields some 60 000 – 80 000 cubic meters of water per day, and is affected by exploitation and pollution by the gold mining industry in the region, deep–level gold mining having markedly impacted on the dolomitic aquifers.  This spring is located in dolomitic rock that is part of the larger Boskop–Turffontein dolomite compartment in the Transvaal Basin.  Dolomite or dolostone is a sedimentary carbonate rock, a swath of which runs parallel to the Magaliesberg, and has a tendency to form large underground lakes and reservoirs. The Roman Catholic Diocese of Davenport (Latin: "Dioecesis Davenportensis" ) is a diocese of the Catholic Church for the southeastern quarter of the U.S. state of Iowa.  There are 11438 sqmi within the diocese.  The diocese's eastern border is at the Mississippi River; the northern border comprises the counties of Jasper, Poweshiek, Iowa, Johnson, Cedar, and Clinton; the western border is made up of the counties of Jasper, Marion, Monroe, and Appanoose; and the southern border is the Iowa-Missouri border. The Leon Sinks Geological Area is located on the Woodville Karst Plain in southern and southwestern Leon County, Florida, United States.  It is a mature karstic area on the Upper Floridan Aquifer.  It is one of the most extensive underwater cave systems in the world and connects to Wakulla Springs.
Answer: Mississippi