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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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Methods You are at the introduciton to the NE Florida Atlas
Regional Geology
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Identification of Karst Features from Seismic Patterns
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Methods

Seismic Profiling | Geophysical Well Logs | Map Generation

Index maps that show the hydrography of the region and provide background for navigation tracklines were generated from standard USGS Digital Line Graph (DLG) datasets using Qeoquest CPS-3 software products. The hillshade maps showing topographical relief were generated from USGS gridded datasets using ESRI ArcView 3.0. Seismic profiles were scanned from analog copies. All page layout of figures and text was accomplished with the drawing programs Deneba Canvas, Adobe Illustrator and Adobe InDesign for Macintosh computers. In addition, internet translation was accomplished with Adobe GoLive and Adobe Photoshop.

Reflective horizons from a lake that were laterally continuous and representative of a subsurface feature or the lake bottom were digitized using a standard digitizing table that have been eroded from the areas bordering the lakes have been deposited in the lakes and migrated downward into the space created by dissolution. The elevation of the bottom of these depressions may represent the base level of erosion as constrained by the potentiometric surface of the Floridan aquifer.

The hillshade views (for example, Index Map A) commencing the subsections were generated in ArcInfo from a grid of topographic elevations interpolated rom existing five foot contours depicted on USGS topographic maps. Data is projected to UTM, Zone 17, NAD 1983, 1990 correction and copied to double precision. Location of wells used for gamma log cross sections are included to show the proximity of well data to the study sites.

Hillshade views help emphasize the surface characteristics of the physiographic provinces surrounding the sites profiled. Lake distributions varies within high sand ridges to low-lying flood plains of modern and ancient river systems. The hillshade views also show how the topography greatly effects the surface water drainage. Many of the lakes are concentrated within the higher sand ridges and form depressions in the surface. The concentrations of slightly acidic water within the lakes provides a mechanism for enhanced dissolution of the underlying carbonates and other sediments. Many lakes are closed basins with no external drainage. In many cases, sediments eroded from the lake margins have been deposited in the lakes and migrated downward into the space created by dissolution. the elevation of the bottom of these depressions may represent the base level of erosion as constrained by the potentionmetric surface of the Floridan aquifer.

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)