USGS Groundwater Information
Subsurface Characterization of Selected Water Bodies in the St. Johns River Water Management District, Northeast Florida
By Jack L. Kindinger1, Jeffrey B. Davis2, and James G. Flocks1
Fluid exchange between surficial waters and groundwater, as well as the processes that control this exchange, are of critical concern to water management districts and planners. Digital high-resolution seismic systems were used to collect geophysical data from more than 40 lakes and rivers of northeastern Florida. Seismic data acquisition in the past has been only partly successful for imaging lake subbottom geology; however, the use of digital seismic technology has greatly enhanced potential applications. Seismic profiles collected from sites in northeastern Florida have demonstrated the potential application of these techniques in understanding the formation of individual lakes. In each case study, geologically controlled solution and/or mechanical processes determined the geomorphology of lakes and evidence of these processes may be seen in seismic profile. Processes that control lake development are twofold: 1) karstification or dissolution of the underlying limestone, and 2) collapse, subsidence, or slumping of overburden to form sinkholes. Initial lake formation is directly related to the karst topography of the underlying host limestone (Fig. 1). Lake size and shape are factors determining the thickness of overburden and size of the collapse or subsidence, and/or the clustering of lake-forming depressions.
Lake evolution follows sequential stages to maturity that creates progression through the following geomorphic types (Kindinger and others, 1999, 2000) (Fig. 2):
Most lakes in this study are small (less than1-km diameter) making stratigraphic correlation from lake to lake difficult. Seismic profiles of subsurface features were used to define the lacustrine geologic history and to locate possible breaches in the confining layer that maintains these lakes (Fig. 3). Six types of acoustic signatures were identified from the seismic profiles to describe the structural history of each lake (Fig.4). Using these criteria, Florida lakes can be classified by size, sediment fill, subsurface features, and geomorphology. Classification of lakes utilizing digital seismic technology has led to a better understanding of the interaction between the geology and hydrology of central Florida.
Kindinger, J. L., Davis, J. B., and Flocks, J. G.1999, Geology and Evolution of Lakes in North-Central Florida: Environmental Geology, v. 38:4, p. 301-321.
Kindinger, J. L., Davis, J. B., and Flocks, J. G., 2000, Subsurface Characterization of Selected Water Bodies in the St. Johns River Water Management District, Northeast Florida: US Geological Survey Open-File Report 00-180, 46 p.
In Eve L. Kuniansky, editor, 2001, U.S. Geological Survey Karst Interest Group Proceedings, U.S. Geological Survey Karst Interest Group Proceedings, St. Petersburg, Florida, February 13-16, 2001: USGS Water-Resources Investigations Report 01-4011
The use of firm, trade, and brand names in this report is for identification purposes only and does not consitute endorsement by the U.S. Government.