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Seismic Stratigraphy of the Central Indian River Region
Jack L. Kindinger1, Jeffrey B. Davis, P.G.2, and James G. Flocks1


Northeast Florida Lakes & Rivers Home
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Stratigraphy of the Indian River Region
  Introduction You are at Seismic 
Stratigraphy of the Indian River Region
Jim Flocks
Study Area Location
Figure 1: Location of study area including seismic survey, well logs, and the subsurface fault identified by Bermes (1958) and Schiner and others (1988).
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The geology and and hydrology of the central Indian River region along the central east coast of Florida (Fig. 1) is of critical concern to the St. Johns River Water Management District (SJRWMD). In this area the upward migration of deeper, more saline ground water in the lower Floridan aquifer to the shallower, fresher ground water of the upper Floridan aquifer and above, may impact the water quality of this resource. Higher than normal chloride concentrations occur in wells east of a reported fault within the Indian River south of Johns Island (Bermes, 1958). The nature and extent of the fault is not well defined. High-resolution seismic tools using digital technology were utilized in collecting geophysical data in an attempt to identify the fault. Additionally, the data collected exhibits the benefits of these techniques in understanding the formation of the upper Florida platform. The application of these techniques aid in the management of water resources by identifying the stratigraphy that contain the surface water bodies and the various aquifer systems.

Physiography and Lithology

Beneath Indian River, the horizons of acoustic impedance are generally related to lithologic changes between clays and carbonates within the Hawthorn Group and with the underlying carbonates of the Ocala Limestone. The Hawthorn Group sediments are highly variable, layered sediments that range from poorly indurated sands and shells to clays, and well indurated carbonates (Scott, 1991). The variable bedding in the sediments provide multiple reflections. The upper Ocala Limestone contact is an irregular horizon identified as an erosional karst surface. The limestone has few bedding planes that have sufficient velocity contrasts to produce coherent reflections.

Strata above the Hawthorn are comprised of variable, undifferentiated sediments associated with ridges formed by Plio-Pleistocene barrier island and dune development. The ridges form the Cocoa-Sebastian Ridge, the Sebastian-Juniper Ridge and Upper St. Johns Karst Regions of the Eastern Flatwoods District physiographic provinces described by Brooks and Merrit (1981). The ridges have elevations of less than 28 m (90 ft). The Indian River occupies the interstices of these paleo-ridges and the modern offshore barrier development.

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1 U. S. Geological Survey, St. Petersburg Coastal and Marine Science Center, St. Petersburg, FL 33701
2 St. Johns River Water Management District, P.O. Box 1429, Palatka, FL 32178-1429

Coastal and Marine Program > St. Petersburg Coastal and Marine Science Center > Northeast Florida Lakes & Rivers Home > Seismic Stratigraphy of Central Indian River > Introduction

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