Larger benthic foraminifera from the Middle Eocene

Larger benthic foraminifera (LBF) are common and diverse throughout the Paleogene sediments of southern Tanzania, but have previously been little studied. A recent programme of onshore drilling known as the Tanzania Drilling Project has recovered large proportion of this succession for palaeoclimatic and palaeontological study. The sediment is largely a hemipelagic clay with secondary gravity sediment flow limestones and calcarenites. LBF occur concentrated in the secondary beds and are present in some clay horizons. Planktonic foraminiferal, nannofossil and, in some cases, stable isotope studies of the clays allow the larger benthic foraminiferal ranges to be tied to global stratigraphy. Here we use nine of these drill sites to examine the LBF from the Middle Eocene to Oligocene. Within this interval several global turnover events of long-ranging and widespread LBF genera are known to occur. However, problems with biostratigraphy mean the exact timing and therefore mechanisms remain uncertain. Our study shows that ranges of Tanzanian LBF genera are within known global ranges. Additionally, there is a change in the LBF assemblage with a number of local first and last occurrences of genera during the Bartonian, which may have potential links to the onset of the Mid Eocene Climatic Optimum.____________________________________________________________________________________