East Antarctic Ice Sheet fluctuations during the Middle Miocene Climatic Transition inferred from faunal and biogeochemical data on planktonic foraminifera (ODP Hole 747A, Kerguelen Plateau)

This research focuses on a detailed study of faunal and biogeochemical changes that occurred at ODP Hole
747A in the Kerguelen Plateau region of the Southern Ocean during the middle Miocene (14.8-11.8 Ma). Abundance
fluctuations of several planktonic foraminiferal taxa, stable oxygen isotope and Mg/Ca ratios have been integrated as a
multi-proxy approach to reach a better understanding of the growth modality and fluctuations of the East Antarctic Ice
Sheet (EAIS) during this period. A 7°C decrease in Sea Surface Temperature (SST), an abrupt turnover in the planktonic
foraminiferal assemblage, a 1.5‰ shift towards heavier δ¹⁸O values (Mi3 event) and a related shift towards heavier
seawater δ1¹⁸O values between 13.9 and 13.7 Ma, are interpreted to reflect rapid surface water cooling and EAIS
expansion. Hole 747A data suggest a major change in the variability of the climate system fostered by EAIS expansion
between 13.9 and 13.7 Ma. Ice sheet fluctuations were greater during the interval 14.8-13.9 Ma compared with those
from 13.7 to 11.8 Ma, whereas the latter interval was characterized by a more stable EAIS. In our opinion, the middle
Miocene ice sheet expansion in Antarctica represents a first step towards the development of the modern permanent ice
sheet