Late Pliocene continental climate and vegetation variability in the Arctic-Atlantic gateway region prior to the intensification of Northern Hemisphere glaciations

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We describe Pliocene palynological assemblages from ODP Hole 910C on the Yermak Plateau, Arctic Ocean. Analysis of high-resolution (~10 ± 3 ka) sampling allows us to detect changes in late Pliocene vegetation biomes corresponding to climatic variability between ~3.4 to 2.6 Ma. Findings show that a cool temperate and mixed boreal forest ( Pinus-Tsuga-Picea-Alnus-Ulmus community) initially dominated the Arctic-Atlantic gateway region. Following the onset of Marine Isotope Stage M2 cooling, ~3.3 Ma, there was a marked decline in vegetation coverage (low abundance of Pinus, Abies community). The mid Pliocene warm period that followed at ~3.2 to 3.0 Ma showed an increase in percentage of thermophilic and moist boreal taxa ( Tsuga-Thuja- Cupressaceae -Betula-Ilex community) suggesting influx of warm Atlantic Current. The dominance of Pinus-Ulmus persisted until ~3.0 Ma. Intermittent cooler and warmer periods occurred after 2.9 Ma, with an increase in herbaceous pollen and cryptogamic spores. This was followed by an abrupt change at ~2.73–2.64 Ma marked by a prominent shift from taiga to tundra-steppe vegetation, and coinciding with the intensification of Northern Hemisphere Glaciation ~2.65 Ma. Occurrences of Impatiens pollen indicates frost-free conditions in the region until ~2.7 Ma. Our high resolution analysis of palynological assemblages synchronizes closely with the Marine Isotope record, in general; however, we show that the mid Pliocene warm period was interrupted by short spells of intermittent cooler periods. • Palynological succession ~3.40 to 2.62 Ma indicate biome change in ODP Hole 910C, Yermak Plateau. • Mixed boreal forest dominated until Marine Isotope Stage (MIS) M2 (~3.30 Ma ago). • During 3.21 to 3.02 Ma pollen taxa indicate warmer period obstructed by two cooling phases. • A shift from Taiga to Tundra-steppe vegetation was recorded between ~2.73–2.64 Ma and Impatiens pollen shows frost-free climate. • The intensification before Northern Hemisphere Glaciation was characterised by intermittent short-term interstadials.