Rare Antarctic fossils reveal extinction of tundra before full polar clima...( (Boston) An international research t...)

(Boston) An international research team in Antarctica led by David Marchant, an associate professor of earth sciences at Boston University, has reported the discovery of exceptionally well-preserved freshwater fossils including mosses, microscopic one-celled algae, known as diatoms, small fresh water crustaceans, and insects that represent the last traces of tundra in the southernmost region of the continent before a dramatic and enduring cooling occurred some 14 million years ago.

These rare fossilized terrestrial organisms, from the McMurdo Dry Valleys sector of the Transantarctic Mountains, were uncovered in sediments from a former ice-free lake, which served to pinpoint the inception of modern polar-desert conditions in Antarctica. The fossil discoveries are also the first to be found in the area even though other scientific expeditions have been visiting this southern region since the first expedition more than 100 years ago.

"The fossils and surrounding sediments are extremely well preserved," said Marchant. "They tell us that the landscape has changed very little in 14.1 million years, and that at the time the fossils lived the climate in this sector of Antarctica was similar to that of southern South America today. The organisms died out suddenly by 13.9 million years ago, and since that time interior Antarctica has been in a perpetual deep freeze, with most of the interior ice remaining relatively stable and frozen. The exact cause of this dramatic climatic shift, one of the most significant over the last 65 million years, remains unknown"

Marchant's comments follow the August 4th publication of "Mid-Miocene Cooling and the Extinction of Tundra in Continental Antarctica" in the Proceedings of the National Academy of Science.

Marchant, along with Adam R. Lewis, a former Boston University graduate student (Ph.D,2005) who discovered the fossils while working under Marchant, are the first of 13 authors on the pape
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