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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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Orange Lake
Alachua County, Florida

Introduction | Subsurface Characterization: Southeast Area | North Area | Southwest Area

Subsurface Characterization: Southwest Area

The southwest area consists of a broad flat bottom with a bathymetry very similar to that in the southeast and north areas, except for the collapse sinkhole (type 5, D-D') near the southwestern shore. The sinkhole has completely breached the confining unit. It is possible that other features are present but access was limited by aquatic weeds and the southwest area could not be completely surveyed.

Seismic profile for D-D'
Profile D-D'

The clustered collapse sinkholes are near the southwestern shoreline adjacent to Heagy-Burry Park and boat ramp. Observations by scuba divers indicate that there is a downward flow of water from the lake into one of the sinks (Spechler and Wilson, 1992). Reports by Pirkle and Brooks (1959b) and Spechler and Wilson (1992) indicate a direct hydraulic connection with the aquifer. During the 1956 drought, water from Orange Lake could be seen draining into the collapse sinkhole of Heagy-Burry Park. Profile D-D' (above) shows the steep slope and fault blocks of the sinkhole. The mass movement of limestone blocks would open pathways for water to migrate along the fractures. Sediment slumping along the steep flanks of the sinkhole also are visible and are part of the natural process that plugs the doline. Adjacent to the collapse are evidence of adjacent cover subsidence sinkholes that ultimately may coalesce in the sinkhole complex.

Three-dimensional bathymetric grid of the clustered sinkholes near Heagy-Burry Park.
Bathymetric contour and mesh plot of the sinkhole complex at Heagy-Burry Park, Lake Orange.

Three-dimensional bathymetric grid of the clustered sinkholes near Heagy-Burry Park.
Aerial photograph and contour overlay of the sinkhole complex in Orange lake.
A three-dimensional bathymetric grid of the clustered sinkholes near Heagy-Burry Park is shown above. The grid model was constructed using the two-way travel time for the lake-bottom reflection (HRSP). Two collapse sinkholes and two adjacent subsidence features are evident from this model. It is not clear if the features are remnants from the sinkhole that was observed in 1956 or are sinks that have formed since. Past reports (Rowland 1957, Jessen 1972) indicate that a single hole approximately 63 m (20 ft) in diameter was exposed. A temporary sandbag and earthen dam emplaced around the hole subsequently collapsed into the hole. Large quantity of fill, a storage tank, and junked vehicles were also placed into the hole. Remnants of the dam, and hence the most northern boundary of the 1956 sink, can presently be seen about 10 m offshore from the park. The satellite overlay figure at right shows the contours of the sinkhole superimposed on an enlarged aerial photograph of the Heagy-Burry Park area. The photo and overlay show the extent of the collapse and subsidence features, including a sinkhole on land in the southeastern portion of the photograph. An area east of the boat ramp is continually subsiding and fill material is periodically emplaced in the depression. Though the limits of the sinkhole observed in 1956 are not known, it is clear that this area represents a sinkhole complex that is still quite active and expanding.

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)