MOLLUSCAN RESPONSE ACROSS THE EOCENE-OLIGOCENE TRANSITION: TANZANIA DRILLING PROJECT SITES 11, 12 AND 17
Complete sections through the EOT containing molluscs are rare, due to associated sea-level fall across the boundary and a lower preservation potential of molluscs compared to microfossils such as foraminfera. However, three Tanzania Drilling Project sites, 11, 12 and 17 contain a record of small, but exceptionally well preserved, gastropods (including pteropods) and bivalves within hemi-pelagic clays which continuously span the EOT. Extensive studies of the nannofossils, planktonic foraminifera, LBF and stable isotopes have been carried out allowing the sites to be well correlated to global bio and chemo-stratigraphy. This unique record enables the response of the mollusc assemblage to be compared with the exact timing of the events of the transition, allowing further insight into ecological changes across this major climatic event. In contrast to other records, molluscan abundance increases across the EOT, indicating a possible increase in nutrients through the transition and further suggesting that de-stratification of the water column may have occurred during this interval.