Bivalve Paleoecology: Key to the Environmental Stratigraphyof a Pliocene Sedimentary Sequence

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In the course of previous research on patterns of biogeography, extinction, and phyletic evolution for Western Atlantic Bivalvia during late Neogene time, I have made extensive collections of the early Pliocene fauna of a shell pit at Sarasota, Florida. This fauna is spectacular for its richness (more than a thousand species of mollusks, about 180 of them bivalves) and for its excellent state of preservation. In the course of my work, I have concluded that the vertical sequence of facies in the pit records the transgression of a barrier-island-lagoon complex, exemplifying Walther's Law. Transgressive sequences of this type are rare in the stratigraphic record because rapid relative rises of sea level usually destroy barrier island and lagoonal facies or cause them to jump inland. I am developing a model to explain why the transgressive sequence has been preserved at Sarasota - a model that I believe has general significance . This proposal is for funding to support more detailed study of the stratigraphic units in the Sarasota pit, more thorough collection of their faunas, and full development of the stratigraphic model. Ultimately, I will also produce a taxonomic-biogeographic monograph on the total bivalve fauna, which represents the little-studied temporal equivalent of well-known faunas to the north (northern Florida to Virginia: the Jackson Bluff, Duplin and Yorktown faunas). It is crucial that the field work in Sarasota be conducted now because the pit will soon be flooded.