Palynomorphs from a sediment core reveal a sudden remarkably warm Antarctica during the middle Miocene

Abstract

An exceptional triple palynological signal (unusually high abundance of marine, freshwater,
\nand terrestrial palynomorphs) recovered from a core collected during the 2007 ANDRILL
\n(Antarctic geologic drilling program) campaign in the Ross Sea, Antarctica, provides constraints
\nfor the Middle Miocene Climatic Optimum. Compared to elsewhere in the core, this
\nsignal comprises a 2000-fold increase in two species of dinofl agellate cysts, a synchronous fi vefold
\nincrease in freshwater algae, and up to an 80-fold increase in terrestrial pollen, including
\na proliferation of woody plants. Together, these shifts in the palynological assemblages
\nca. 15.7 Ma ago represent a relatively short period of time during which Antarctica became
\nabruptly much warmer. Land temperatures reached 10 C (January mean), estimated annual
\nsea-surface temperatures ranged from 0 to 11.5 C, and increased freshwater input lowered
\nthe salinity during a short period of sea-ice reduction.