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

  1. Sophie Warny1,
  2. Rosemary A. Askin1,
  3. Michael J. Hannah2,
  4. Barbara A.R. Mohr3,
  5. J. Ian Raine4,
  6. David M. Harwood5,
  7. Fabio Florindo6 and
  8. the SMS Science Team*
  1. 1Department of Geology and Geophysics, and Museum of Natural Science, E235 Howe-Russell, Louisiana State University, Baton Rouge, Louisiana 70803, USA
  2. 2School of Geography, Environment and Earth Sciences, Antarctic Research Centre, Victoria University of Wellington, PO Box 600, Wellington, New Zealand
  3. 3Museum of Natural History, Collections, Invalidenstrasse 43, 10115 Berlin, Germany
  4. 4GNS Science, PO Box 30368, Lower Hutt, New Zealand
  5. 5Department of Geosciences, and ANDRILL Science Management Office, 214 Bessey Hall, University of Nebraska–Lincoln, Lincoln, Nebraska 68588-0340, USA
  6. 6Istituto Nazionale di Geofisica e Vulcanologia, Via di Vigna Murata 605, 00143 Rome, Italy

    Abstract

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

      • Received 13 February 2009.
      • Revision received 27 May 2009.
      • Accepted 2 June 2009.
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    1. doi: 10.1130/G30139A.1 Geology October 2009 v. 37 no. 10 p. 955-958
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