Abstract Introduction Material & Methods Lithostratigraphy Petrography, Biostratigraphy & Sr-isotope Analysis Conclusions References Figures Tables Appendix 1 Appendix 2 PDF version

Introduction

Figure 1. Map of Collier and Monroe Counties, southwestern Florida (inset) showing locations of the corehole sites, numbered and identified on the figure, and the lines of cross-sections, A-B, B-C, and A-C, shown in Figures 10, 11, and 12. [larger image]

In 1996, seven cores were recovered in western Collier County, in the area between Alligator Alley (I-75), Tamiami Trail (U.S. Route 41), State Route 29, and State Route 951, as part of a joint USGS and FGS project (fig. 1). The objective is to acquire subsurface geologic and hydrologic data in southwestern Florida to support ground-water modeling in that region, thereby expanding the utility of these models for land and water management. The lithology and geophysics of these cores were summarized by Weedman and others (1997). This report describes the lithostratigraphy, X-ray diffraction analyses, petrography, biostratigraphy, and strontium (Sr) isotope stratigraphy of the same cores.

Previous geologic and hydrologic studies were discussed by Weedman and others (1997). The current model for the surficial aquifer system of southwestern Florida consists of two aquifers: the water-table and the lower Tamiami aquifers, separated by a semi-confining unit (Southeastern Geological Society, 1986; Bennett, 1992). An additional aquifer has been identified within the surficial system in south-central and southeastern Florida. The gray limestone aquifer, described from Dade County by Fish and Stewart (1991), is assumed to extend westward into Collier and perhaps Monroe counties, and may be correlative with the lower Tamiami aquifer. In this study we have identified the Tamiami Formation and we recognize an unnamed formation below the Tamiami Formation. Some of the unnamed formation is possibly correlative with a newly described and proposed formation recognized in the Florida Keys to the south, the proposed Long Key Formation (Cunningham and others, 1998). The Tamiami Formation is the primary stratigraphic unit comprising the water table aquifer, and perhaps some of the lower Tamiami aquifer, in southwestern Florida. The Hawthorn Group and its constituents, the Peace River and Arcadia Formations, were not recognized in any of the cores discussed here, although the unnamed formation may be correlative in part.

Acknowledgments

We thank drillers Jim Trindell (FGS), Don Queen (USGS), Alex Howell (FGS), Frank Rush (FGS), and Roger van Landingham (FGS). We also extend our thanks to Bob Henry from Collier-Seminole State Park, Mike Owen, Jolen Mabry, Jim Nelson, and the late Eddy Lowery from Fakahatchee Strand State Preserve, Erv Crosby and Sonja Durrwachter of the Florida State Division of Forestry, Mel Fisher and Mike Quigley of the Southern States Utilities Company, Gary Susdorf of Viro Group, Inc., and Kevin Rohrer of SFWMD in West Palm Beach, Florida. Processing for dinocysts was done by Tom Sheehan and Lisa Weimer; Tom Sheehan also assisted in the collection of samples and Lisa Weimer performed preliminary examination of samples. Mollusk samples were collected with the assistance of Harley Means and Tom Sheehan. Mollusk sample preparation was by Steve Wandrei and Jill D'Ambrosio. Sample preparation for foraminifers was performed by Ian Graham and Kevin McKinney. We wish to thank John Jackson (USGS) for sharing his expertise on the use of the Diano X-ray diffraction spectrometer, calibration, and interpretation of results. We thank Frank Dulong (USGS) for his guidance in sample preparation and the interpretation of X-ray diffraction results. Bruce Wardlaw and Rob Weems provided valuable comments on the manuscript.