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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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Introduction
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Regional Geology
Karst Development & Characterization
Sinkhole Lake Evolution & Effect of Urbanization
Identification of Karst Features from Seismic Patterns
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Orange Lake
Alachua County, Florida

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

Subsurface Characterization: North Area

The north and central areas of Orange Lake are geologically similar and will be combined and discussed as one area. The lake bottom and subsurface are relatively flat and intact with small subsidence features throughout. The unconsolidated surficial sediment is a sandy clay that, along with the shallow water depth, produces strong multiple reflections that mask much of the geologic data (type 1, C-C', below). The vertical features in the cross section may indicate the early stages of a subsidence sinkhole, with the central area actively subsiding and/or collapsing. The high angle reflections throughout the profile may represent stress fractures created by slumping as the overburden accommodates dissolution at depth. The features may also represent dissolution pipes through the overburden, indicating a breach in the confining layer.

Seismic profile for C-C'
Profile C-C'

Features in the northern portion of the lake are generally small (1 to 10 m across, 3 to 33 ft) and tend to be isolated. Distribution and size of features in this area are different than the features in the southeast that tend to cluster together to form larger (>100 m, 328 ft) structures. Surface features and shallow horizons (< 2 m, 66 ft) were seen in the HRSP data that indicated a number of subsidence sinkholes in this area (type 3) and type 4 karst features that have clustered to form disturbed areas in the subsurface, up to 40 m (131 ft) across. Most of the area between Samsons Point and Boardman show some form of subsidence.

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 02, 2016 @ 11:25 AM (JSS)