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Coastal & Marine Geology Program > Center for Coastal & Regional Marine Studies > Geologic Characterization of Lakes and Rivers of Northeast Florida > OFR 00-180

Subsurface Characterization of Selected Water Bodies in the St Johns River Water Management District, Northeast Florida

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Identification of Karst Features from Seismic Patterns
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Lake Hammond
Lake County, Florida

Introduction | Subsurface Characterization

Subsurface Characterization

Lake Hammond
Lake Hammond. Black likes show profile locations.
Seismic profiles from Lake Hammond show a strong bottom reflection, possibly from well-sorted sands. The strong bottom reflection results in multiples seen throughout the data that obscure some of the record (A-A', B-B'). Noise below the topographic lows in the profiles also obscure some of the record (gray lines, A-A'). This noise could be a result of the accumulation of organic material in the depressions which attenuates the acoustic signal. The subsurface is characterized by numerous small depressions with mid-to low-angle reflections dipping toward the centers of the depressions (B-B'). Concentric reflections may extend to depth in the profile (marked by red dashed lines in profiles). These features may represent solution pipes dissolved into the karst subsurface. These areas of subsurface depressions have been plotted in the Distribution of Features map (brown line), relative to bathymetric lows (blue line) to reveal their relationship.

Seismic Proflie A-A'
Profile A-A'

Seismic Proflie B-B'
Profile B-B'

Distribution of features in Lake Hammond.
Lake Hammond Distribution of features
(noted from seismic profiles)
The seismic reflection data from Lake Hammond overall is similar to that of its neighbor, Lake Dixie. However, perhaps because of the lake's smaller size, the data quality is generally poorer. The deeper reflection seen in Lake Dixie that correlates with gamma logs to represent the top of the Ocala Limestone (Lake Dixie, blue line), cannot be seen as readily in the Lake Hammond profiles. Certain traces of a horizon are apparent in some of the profiles (blue line, B-B'), however because of data quality the reflection is difficult to trace. Still, it is possible to assume that differential dissolution in the Ocala Limestone could lead to subsequent subsidence in the overlying sediments of the Hawthorn Group and the undifferentiated fill.

Coastal & Marine Geology Program > Center for Coastal & Regional Marine Studies > Geologic Characterization of Lakes and Rivers of Northeast Florida > OFR 00-180

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Updated December 05, 2016 @ 11:25 AM (JSS)