LARGER BENTHIC FORAMINIFERA OF FLORIDA AND THE EOCENE OLIGOCENE TRANSITION

A series of global overturning events in the larger benthic foraminifera (LBF) occur in the upper Eocene, culminating with the widespread, rapid extinction of several long-ranging taxa around the Eocene – Oligocene transition (EOT) – one of the most dramatic events of the Cenozoic. Whilst integrated stratigraphic studies have helped to refine the timing of LBF overturning events within the Tethys and Indo Pacific regions with respect to global bio- and chemo-stratigraphic records, little recent work has been carried out in the Americas. Shallow-water carbonate deposits are well-known from the Eocene of the U.S. Gulf Coast and Caribbean. These deposits frequently contain abundant larger benthic foraminifera (LBF). The American LBF assemblages, are distinctly different to those of Europe and the Indo-Pacific. Within the Eocene, they lack the huge diversity of Nummulitesseen elsewhere, instead assemblages are often dominated by lepidocyclinids, which do not occur in the rest of the world until at least the upper part of the lower Oligocene.

It is therefore essential the American bioprovince is included in studies of LBF evolution, biodiversity and climate events to understand these processes on a global scale. However, this is currently not the case. Inclusion of the Americas to such studies is hampered by a lack of up to date taxonomy and comprehensive biostratigraphy for the region. Numerous detailed taxonomic studies were carried out during the 1950s-1970s, most notably by Cole and Vaughan. However, little work has been carried out since, particularly in the Gulf Coast region, which includes the thick Eocene Ocala Limestone and a variety of LBF-bearing carbonates of Early Oligocene age.

Here we present the LBF ranges from previously unpublished sections, one of which spans the EOT, along with initial results from integrated stratigraphic analyses of core recovered by the Florida Geological Survey, spanning the lower Eocene to Oligocene. Though in its early stages this work has important implications for refining the timing of LBF events with respect to the global isotope curve, and increasing understanding of the response of the shallow marine environment to major climatic and oceanographic changes.