Late Neogene Oceanographic Change along Florida's West Coast: Evidence and Mechanisms

Evidence from vertebrate and invertebrate fossil assemblages and isotopic analyses supports the hypothesis that during the Pliocene biological productivity in the eastern Gulf of Mexico was considerably higher than during the Pleistocene and Recent. Late Pliocene faunal changes in the eastern Gulf, Western Atlantic, and possibly elsewhere may have resulted, at least in part, from this shift in productivity conditions. Even if marine temperatures declined, paleontological and isotopic data appear to require a change in productivity in the Late Pliocene. This putative productivity decline may have been caused by some combination of causes at three geographic scales: (1) globally-marine productivity may have fallen due to changes in continental weathering; (2) regionally-North Atlantic productivity may have fallen as a result of initiation of North Atlantic Deep Water formation (possibly a consequence of formation of the Central American Isthmus, CAI) and resulting net transfer of nutrients to the Pacific; (3) locally-productivity may have fallen only in the eastern Gulf, due to circulation changes assisted with the formation of the CAI, and an accompanying decline in upwelling. The relative importance of processes at these three geographic scales remains unclear. The probable role of the formation of the CAI in two of the three, however, points to the importance of further investigation of the paleoceanographic consequences of this event for Late Cenozoic biological communities of the region.