Abstract Introduction Background Methods Seismic Sequences Discussion >Conclusions & Acknowledgments References Tables PDF Version

High-resolution seismic-reflection data from the Caloosahatchee River have been correlated to lithostratigraphy, nannofossil biostratigraphy, and strontium-isotope chemostratigraphy from six continuously cored boreholes drilled along the bank of the river. Three seismic sequences were identified from correlation of seismic stratal packages to lithofacies changes and unconformities in cores, and corroborated with the chronostratigraphic data. The seismic sequences document a Middle to Late Cenozoic (1) cessation in carbonate-ramp sedimentation on the southeastern part of the Florida Platform, (2) subaerial erosion of the ramp, (3) flooding of the exposure surface during an approximate 100 m relative rise in sea level, (4) filling of resulting accommodation by siliciclastics, and (5) return to carbonateplatform growth. The seismic and core data provide new evidence that a large Miocene to Early Pliocene fluvial-deltaic system delivered an enormous supply of siliciclastics that accumulated on the southeastern part of the Florida Platform. Recognition of evidence for a fluvial-deltaic system is an important contribution to a long debate about the transport mechanism of these quartz sands, since their early reporting by Vaughan (1910). Development of the inferred fluvial-deltaic system was made possible as a result of connection of the platform top to a continental source of sediments and infilling of significant paleotopography. We infer that the substantial paleotopography must have controlled the dispersal of fluvial sediments across the Florida Platform as far south as the present-day shelf edge of the shallow Quaternary carbonate shelf of the Florida Keys. The southward progradation of the Late Tertiary siliciclastics was critical to recovery of carbonate growth on the southeastern Florida Platform that ceased during the Miocene. Had these quartz sands not filled accommodation near the southeastern edge of the Florida Platform it is likely that the return to shallow-marine carbonate deposition as a reef-rimmed shelf during the Quaternary would not have occurred. This work shows that the southeastern Florida Platform is an ideal location to refine our understanding of the influence of the mixing of siliciclastics and carbonates on platform evolution.

Clyde Dabbs and Eric Swain are thanked for initiating the project. The U.S. Geological Survey and the South Florida Water Management District cooperatively funded this research. Jim Trindell, FGS, expertly drilled the coreholes. Robert Renken, Jack Kindinger, and Tom Scott provided early technical reviews. Steve Goodbred, Michael Blum, David Budd, and an anonymous reviewer are thanked for final critical reviews. Anthony Brown assisted with collection of field data.