ARCTIC OCEAN BENTHIC FORAMINIFERAL FAUNAL CHANGE ASSOCIATED WITH THE ONSET OF PERENNIAL SEA ICE IN THE MIDDLE MIOCENE

Understanding how Arctic Ocean deep-water ecology responded to past climatic events is of importance in assessing the region's sensitivity to environmental change. Here we present the first quantitative Miocene-Pliocene benthic foraminiferal records from the central Arctic Ocean, Lomonosov Ridge, IODP Hole M0002A. Despite significant dissolution and the absence of calcareous tests, these data show a significant faunal change occurred at similar to 14 Ma, characterized by a change from an older, relatively diverse assemblage including Reticulophragmium pusillum, Ammo-lagena clavata, and Reacurvoides brideauxi, associated with open-ocean environments and a paleodepth probably >200 m, to a younger assemblage dominated by Rhabdammina spp. and the endemic Arctic benthic foraminifera Alveolophragmium polarensis. Sedimentologic proxies indicate the onset of perennial sea ice in the central Arctic Ocean likely occurred in conjunction with the faunal change, suggesting that this onset and increased ice rafting had a long-term impact on bottom-water ecology in the central Arctic Ocean. This ecologic change may have been related to changes in the type, quantity, and duration of organic carbon flux, which may also explain the documented increase in total sedimentary organic carbon at the same time, possibly indicative of increased productivity. In the younger section of M0002A, from similar to 12.6 Ma, abundances are too low for clear paleoecologic interpretations.