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April 22, 2008

Antarctica: A Keystone in a Changing World ISAES X -2007
The 10th International Symposium on Antarctic Earth Sciences was convened at the University of California, Santa Barbara in August 2007 where 350 researchers (group photo) presented talks and posters on topics including climate change, biotic evolution, magmatic processes, surface processes, tectonics, geodynamics, and the cryosphere.  The symposium resulted in 108 peer reviewed papers and 217 extended abstracts that are published online (http://pubs.usgs.gov/of/2007/1047/). A proceedings book has also been published by The National Academies Press. See Publications for details.

Advances in our understanding of Antarctic tectonics were many, often involving techniques that provide information under ice sheets or from proxies such as glacial till to provide clues on provenance. Goodge and coworkers reported  a 1440 Ma A-type granite boulder from  glacial till from the Nimrod Glacier that can be matched to granites from the North American Laurentian province, supporting the postulated (SWEAT hypothesis) fit of East Antarctica and North America over 1 billion years ago.  Considerable debate concerned the formation of the Transantarctic Mountains and the role of plateau collapse. It was proposed that collapse of a  plateau during Cretaceous East-West Antarctic extension left a remnant edge forming the proto-mountains, since enhanced by Cenozoic rift-flank uplift.  Bialas and colleagues presented the concept and numerical model, Fitzgerald and colleagues the geological evidence, and Huerta some geomorphic evidence.

Definitive new findings emerged on the evolution of life on Antarctica. Insights into Gondwana ecosystem dynamics are being gleaned from tracks of animals in Devonian deserts, the climate records in Permian, Triassic and Jurassic floras and the Triassic and Jurassic reptiles and dinosaurs of the Transantarctic Mountains.  The newly identified fossil plant record shows that, even during the Antarctic icehouse, the continent supported a diverse ecosystem. Recent discoveries of fossil plants and insects by Francis, Ashworth and coworkers showed that small Nothofagus bushes, mosses and beetles persisted in Antarctica during the mid-Miocene. Kirschvinck examined the biochemical role of early ice sheets and the development of earth’s atmosphere linking intense global glaciations and atmospheric oxygen generation suggesting that ice sheets serve as an inorganic mechanism driving the evolution of oxygen-mediating enzymes.

Significant progress has been made regarding Antarctica’s Neogene-Pleistocene climate and its role in the global climate system. Studies of geologic proxies at various times-scales are underway to resolve the paleoclimatic events.  Several different initiatives are on-going including ANDRILL (ANTarctic geological DRILLing), SHALDRIL (SHALlow DRILling) and a Wilkes Land margin IODP cruise. Naish, Powell and the ANDRILL scientists presented the results of first drilling season, a novel record of at least 60 ice sheet fluctuations in the past 13 Ma, with indications of both warmer-than-present climate and ice sheets in the pre-Pleistocene period.

New discoveries on subglacial lakes were presented at the symposium, including outlining tectonic controls for formation of the lakes, documenting the interconnection of lakes, and describing  the recent discovery that subglacial lakes and ice streams lake-water discharge into the oceans. Leitchenkov presented the first dates from the interior of East Antarctica, a detrital zircon recovered from the Vostok ice core that clustered between 0.8-1.2 Ga and between 1.6-1.8 Ga.

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