PALEONTOLOGICAL CHARACTERIZATION OF THE AND-2A CORE, ANDRILL SOUTHERN MCMURDO SOUND PROJECT, ANTARCTICA

The palaeontological yield of the 1138.54 metre-long AND-2A sedimentary rock core provides unique documentation of Neogene environments in the Ross Sea region of Antarctica. Especially important is the biological legacy of the climatically crucial ‘mild’ middle Miocene phase. Diatom-bearing units provide key information for stratigraphic intervals never previously recovered from locations proximal to the Antarctic continent and constrain the age model for the AND-2A core. Benthic calcareous (and agglutinated) foraminifera were present at many levels; remarkable is the occurrence of planktonic taxa only seldom found in the Neogene nearshore record of the Ross Sea region. The sporadic occurrence of calcareous dinoflagellate remains (thoracosphaerids) is consistent with warmer-than-present seawater during the Miocene. Marine palynomorphs are almost ubiquitous, although their abundance and diversity are variable. Pollen and spores from the middle Miocene section suggest a mossy tundra vegetation and represent the first stratigraphically-constrained record of terrestrial vegetation in Victoria Land during this time. Fragments of lignin-rich organic matter (huminite-vitrinite and inertinite groups) are particularly predominant during the Miocene climatic optimum, and continue into the Pliocene. Macrofossils are reasonably common throughout the core. Polychaete worm tubes were almost ubiquitous. Especially remarkable is the bivalve record (mainly pectinids), with 4-5 different taxa pointing out a mild climatic situation in the Miocene nearshore.