MIDDLE PLIOCENE CORAL REEFS OF THE FLORIDA PLATFORM

Coral faunal records of the Tamiami Formation document a northern expansion of reef development along the west coast of Florida during the mid-Pliocene warm period (MPWP). U-Pb radiometric dating based on subsamples of Solenastrea bournoni produced an age of 2.99 ± 0.11 Ma. This age constrains reef development of the Tamiami Formation to the period of Plio-Pleistocene faunal turnover, following final closure of the Central American Seaway (CAS) but prior to major Northern Hemisphere Glaciation (NHG). Coral faunal analyses are based on a total of 1,647 zooxanthellate coral specimens collected along a 165 km stretch of the west Florida coast. A total of 60 coral species occur within the Tamiami Fm, with faunal assemblages ranging from less than 68% extant taxa to over 90% extant taxa. The Tamiami collections could be split into a southern “reef” assemblage with high diversity of stenotopic taxa and a northern “non-reef” assemblage with lower diversity eurytopic taxa. The southern reef assemblage has been designated the Golden Gate Reef Member and contains framework buildups of the dominant tropical taxa Stylophora affinis, Orbicella annularis, and Acropora cervicornis. Canonical correspondence analysis of 46 Late Miocene to Recent reef coral assemblages from the Caribbean region shows the Tamiami Formation to be unique among other Neogene shallow water coral assemblages of the Caribbean and western Atlantic. The Tamiami Fm is most clearly distinguished from the overall Caribbean temporal trend by the presence of eurytopic taxa Septastrea crassa, Septastrea marylandica, Mussismilia hispida, and the endemic taxa Diploria sarasotana, Oculina sarasotana, Siderastrea dalli, Scolymia sp.A, and Scolymia sp.B. We interpret enhanced west Florida southern reef development during the middle Pliocene to be a product of warmer sea surface temperatures, reduced salinity fluctuations, and higher sea levels. A completely flooded southern Florida Platform would have changed sea surface currents; eliminating cold-water events during winter storms and promoting propagule immigration into the region.