International Geologiical Congress - Oslo 2008

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AAN-02 Cenozoic Antarctic glacial history

 

Antarctic Cretaceous ice: Precursor to Cenozoic glaciation?

 

Jane Francis, University of Leeds (United Kingdom)
Vanessa Thorn, University of Leeds (United Kingdom)
Alan Haywood, University of Leeds (United Kingdom)
James Riding, British Geological Survey (United Kingdom)
Stephen Hunter, British Antarctic Survey (United Kingdom)
Alistair Crame, British Antarctic Survey (United Kingdom)
Rob Raiswell, University of Leeds (United Kingdom)
Jim Marshall, University of Liverpool (United Kingdom)
Peter Frost, University of Exeter (United Kingdom)
Duncan Pirrie, University of Exeter (United Kingdom)
 

 

Although the present major ice sheets on Antarctica became established in the latest Eocene-early Oligocene, ice may have been present on the continent much earlier, even during Cretaceous greenhouse climates. Analyses from deep sea drilling programmes suggest that extensive sea level changes during the latest Cretaceous could have only been caused by the presence of extensive ice sheets on Antarctica and that, following peak Cretaceous warmth, cooling during the Maastrichtian (∼71-65Ma) may have been severe enough for short-term glaciations at high latitudes.

The Maastrichtian sedimentary sequence on the Antarctic Peninsula has thus been investigated to determine the extent of Cretaceous ice. The sequence is dominated by unconsolidated silts and fine sands deposited on a marine shelf, with intervals of glauconite-rich sandstones, indicating that sedimentation rates were periodically extremely low, possibly due to high sea levels. Outsized pebbles are also present within the silts, although their interpretation as glacial dropstones is uncertain. Palynomorph studies indicate little change in terrestrial and marine floras, although the marine dinocyst flora that reflects unstable ocean palaeoecology at the end of the Cretaceous. Oxygen and carbon isotope analyses indicate cool ocean temperatures through the latter part of the Maastrichtian.
Climate simulations for the Maastrichtian using the fully coupled ocean-atmosphere global climate model HadCM3L have been performed to investigate the potential for Cretaceous ice. Results indicate that ice could have been present on East Antarctica with atmospheric CO2 levels 4 x pre-industrial levels. With CO2 concentrations equivalent to 2 x pre-industrial level an East Antarctic ice sheet could have existed that was equivalent in size to the present Greenland ice sheet (∼7m sea level change). Despite the lack of definitive geological evidence, these results suggest that bipolar glaciation was possible, even during the Late Cretaceous greenhouse.

 

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