Three-Dimensional Flow in the Florida Platform: Theoretical Analysis of Kohout Convection at Its Type Locality

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Kohout convection, Floridan aquifer system, Boulder Zone, geothermal, heat flow, dolomitization, groundwater

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Kohout convection is the name given to the circulation of salinegroundwater deep within carbonate platforms, first proposedby F.A. Kohout in the 1960s for south Florida. It is now seenas an Mg pump for dolomitization by seawater. As proposed byKohout, cold seawater is drawn into the Florida platform fromthe deep Straits of Florida as part of a geothermally drivencirculation in which the seawater then rises in the interiorof the platform to mix and exit with the discharging meteoricwater of the Floridan aquifer system. Simulation of the asymmetricallyemergent Florida platform with the new three-dimensional (3-D),finite-element groundwater flow and transport model SUTRA-MS,which couples salinity- and temperature-dependent density variations,allows analysis of how much of the cyclic flow is due to geothermalheating (free convection) as opposed to mixing with meteoricwater discharging to the shoreline (forced convection). Simulationof the system with and without geothermal heating reveals thatthe inflow of seawater from the Straits of Florida would besimilar without the heat flow, but the distribution would differsignificantly. The addition of heat flow reduces the asymmetryof the circulation: it decreases seawater inflows on the Atlanticside by 8% and on the Gulf of Mexico side by half. The studyillustrates the complex interplay of freshwater-saltwater mixing,geothermal heat flow, and projected dolomitization in complicated3-D settings with asymmetric boundary conditions and realistichorizontal and vertical variations in hydraulic properties.

Citation / Publisher Attribution

Geology, v. 35, issue 7, p. 663-666

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