PALEOENVIRONMENTAL RECONSTRUCTION USING BENTHIC FORAMINIFERAL ASSEMBLAGES FROM THE PLIOCENE SHELL BEDS IN SOUTHWEST FLORIDA

There is general agreement that a wide range of paleodepths are represented in the individual shell beds of the Pliocene Tamiami Formation of southwest Florida, but maximum depths remain poorly constrained. Here, we use benthic foraminifera as a paleodepth proxy in comparisons of recent Florida foraminifera from Sarasota and modern coastal, bay and reef habitats, ranging in depth from 0 to 90 meters, and bulk sampled foraminifera from exposures of the Tamiami Formation (Pinecrest beds) and SMR Aggregates Quarries. We used ordination techniques to compare Pinecrest foraminiferal assemblages with modern counterparts, Ammonia-Elphidium & FORAM indices to reconstruct past nutrient levels, & Rarefaction to reconstruct habitat-specific diversity change through time.

Initial work indicates that these Pliocene foraminifera lived in two distinct environments. APAC samples indicate a bay to shallow shelf environment, at depths approximately 10 to 30 meters, with a medium nutrient level. SMR samples indicate a mangrove environment, at depths approximately 0 to .3 meters, with a high nutrient level. APAC species richness is higher than the closest matching modern environments.

Future work will involve further constraining paleoenvironmental conditions through the examination of additional samples of microfossils and mollusks and geochemical analysis.