|
publications > paper > PP 1403-G > hydrogeology > floridan aquifer system > lower floridan aquifer
Hydrogeology, Ground-Water Movement, and Subsurface Storage in the Floridan Aquifer System in Southern FloridaBy Frederick W. Meyer
Hydrogeology of Southern Florida: Floridan Aquifer SystemLower Floridan AquiferThe Lower Floridan aquifer consists chiefly of the Oldsmar Formation and, to a lesser degree, the upper part of the Cedar Keys Formation. Ground water in the Lower Floridan aquifer compares chemically to modern seawater. In the Lower Floridan aquifer are three permeable dolostones of the Oldsmar Formation that are separated by less permeable limestones. The transmissivity of the lower dolostone (locally called the Boulder Zone; Miller, 1986, p. B65-B66) ranges from about 3.2 x 106 ft2/d (Meyer, 1974) to 24.6 x 106 ft2/d (Singh and others, 1983), whereas that for the overlying dolostones is probably an order of magnitude less. In southeastern Florida, hydraulic connection between the lower and intermediate dolostones is inferred from pumping tests and from the presence of sinkholes and fractures; however, hydraulic connection between the intermediate and upper dolostones apparently is poor, and locally the upper dolostone may be more closely related to the middle confining unit than to the Lower Floridan aquifer. In southwestern Florida, drilling data suggest that the dolostones are hydraulically connected, although head data and aquifer tests to confirm this interpretation are lacking. A pronounced temperature anomaly is present in the Lower Floridan aquifer, with the lowest measured temperature (50.5 °F) in a deep disposal well (G-2334) at Fort Lauderdale (fig. 6). Temperatures increase generally from the Straits of Florida inland toward the center of the Floridan Plateau (table 1, fig. 7), and, as previously mentioned, Kohout (1965) hypothesized circulation of cold seawater inland from the Straits of Florida through the lower part of the Floridan aquifer system driven by geothermal heat flow (fig. 1).
Attempts to calculate hydraulic gradients in the Lower Floridan aquifer to verify the direction of ground-water movement have, thus far, been unsuccessful owing to a lack of reliable head data and to transitory effects of tides (ocean, Earth, and atmospheric). However, recent measurements of head and carbon-14 activity, which are discussed in subsequent sections, in the waters of the Boulder Zone at site 9 (fig. 2) in well G-2334 and at site 10 (fig. 2) in well G-2296 substantiate the Kohout hypothesis.
Previous: < Middle Confining Unit | Next: Hydrogeology at Alligator Alley Site > |
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
U.S. Department of the Interior, U.S. Geological Survey
This page is: http://sofia.usgs.gov/publications/papers/pp1403g/flaqsyslow.html
Comments and suggestions? Contact: Heather Henkel - Webmaster
Last updated: 05 January, 2005 @ 02:33 PM(TJE)
