Middle Miocene marine and continental climate and environments at the Wilkes Land margin, Antarctica (IODP 318)

Integrated Ocean Drilling Program (IODP) Expedition 318 accomplished successful drilling of the Wilkes Land margin (East Antarctica) in early 2010. Understanding the development and the dynamics of the cryosphere during the Cenozoic and obtaining high-resolution records of climate variability during the Neogene and the Quaternary were among the main targets. Samples from Site U1356 Hole A, between ~400 (across unconformity U5) and ~100 mbsf are analysed for dinoflagellate assemblages, pollen and spores, TEX86 and MBT in order to unravel marine and terrestrial climate variability during the early to middle Miocene. Results show that dinoflagellate assemblages, dominated by autotrophic species, are indicative of warm ice-free surface waters during the Middle Miocene Climatic Optimum (MMCO). TEX86-derived Sea Surface Temperatures (SSTs) confirm this interpretation. Continental temperatures based on pollen and Mean Annual Temperatures (MATs) as derived from MBT organic proxy indicate a vegetated Antarctic margin with temperate conditions. A clear climate deterioration occurs during the Mid Miocene Climate Transition (MMCT), when dinocyst and pollen assemblages indicate (year-round) sea-ice development and ice-sheets advance, respectively. Notably, SSTs and MATs markedly decrease.