GSA Annual Meeting in Phoenix, Arizona, USA - 2019

Paper No. 1-14
Presentation Time: 11:15 AM


LEBEL, Caitlin P., Department of Geological Sciences, University of Florida, 241 Williamson Hall, Gainesville, FL 32608 and COTTON, Laura J., School of Earth Sciences, University of Bristol, Wills Memorial Building, Queens Road, Bristol, FL BS8 1RJ, United Kingdom

The Eocene-Oligocene Transition (EOT) was an interval of dramatic climatic change and significant overturning in both marine and terrestrial organisms, including the larger benthic foraminifera (LBF). Larger benthic foraminifera are an informal group of foraminifera, defined by their exceptionally large size and complex internal structures, that inhabit the tropical photic zone. Several long-ranging groups of LBF are known to become extinct globally during the EOT. However, the majority of high resolution records across this interval come from the open ocean and very few from the carbonate platform, despite these areas being well known for their high biodiversity. It is therefore essential to include studies of shallow marine EOT records in order to more fully understand the complete ocean system and its response to major climatic shifts.

The American bioprovince contains abundant LBF during the Eocene but the assemblage is different to other parts of the world, the assemblages are dominated by lepidocyclinids, and there are few nummulitids. Whilst elsewhere lepidocyclinids do not occur until the Oligocene and nummulitids are abundant. This also means that the response of LBF assemblages in the Americas to the EOT differs from elsewhere, but little recent work has been carried out in this region.

Here we show the preliminary results from an 800 ft limestone core record recovered from Tallahassee, N. Florida. The core spans the Middle Eocene to Lower Oligocene, and enabled us to study LBF biodiversity and ranges across this interval of major climate change. In order to constrain the timing of LBF events these were coupled with chemo- and nannofossil stratigraphy, making it a unique record for the region. Understanding how LBF respond to the EOT and how this varies geographically will give important insight as to the mechanisms behind extinctions in the shallow marine realm.