BENTHIC FORAMINIFERAL ANALYSES OF EQUATORIAL MID-PLEISTOCENE TRANSITION SEDIMENTS

Samples from IODP Expedition 344 were collected to be processed for combined calcareous nannofossil and foraminiferal analyses over the Mid-Pleistocene Transition (MPT) which occurred between 1.25–0.7 million years ago. The samples from Site U1414, in the equatorial region off Costa Rica, contain excellent benthic foraminifera commonly associated with the mid-Pleistocene extinction event (Stilostomella Extinction Event referred to as SEE). The SEE includes >50 morphospecies and is well documented in DSDP and ODP sites, especially in the Southwest Pacific Ocean. The Stilostomella group has been noted to decrease in abundance and diversity in the late Pliocene with greater extinction rates having been documented between 0.7 and 1.2 Ma. The onset and duration of SEE events from the equatorial regions is only recorded at a couple of locations and comparisons of these and our study may provide a better understanding of the causes and impacts of the most recent benthic foraminifera extinction.

Here, we present foraminiferal ecology data and abundances throughout the MPT. Well-preserved specimens from these samples are used for stable carbon isotopic geochemistry. To determine microhabitat preferences of benthic foraminifera and assess their morphology and calcification with MicroCT scanning. MicroCT scanning was used in order to find volumes of the foraminifera tests. This data can be used to find patterns between individual foraminifera and how this relates to their depths and stable isotopic geochemistry. The findings of this project will provide initial observations and insights into the conditions prevailing at the equatorial region of the Southwestern Pacific during the MPT.