Extinção e resfriamento de tundra

Mid-Miocene cooling and the extinction of tundra in continental Antarctica
¨ Adam R. Lewisa,b,c,d, David R. Marchanta, Allan C. Ashworthc, Lars Hedenase, Sidney R. Hemmingf, Jesse V. Johnsong, Melanie J. Lengh, Malka L. Machlusf, Angela E. Newtoni, J. Ian Rainej, Jane K. Willenbringk, Mark Williamsl, and Alexander P. Wolfem aDepartment of Earth Sciences, Boston University, Boston, MA 02215; bByrd Polar Research Center, Ohio State University, Columbus, OH 43210; cDepartment of Geosciences, North Dakota State University, Fargo, ND 58105; eDepartment of Cryptogamic Botany, Swedish Museum of Natural History, Box 50007, SE-104 05 Stockholm, Sweden; fLamont–Doherty Earth Observatory, Columbia University, Palisades, NY 10964; gDepartment of Computer Science, University of Montana, Missoula, MT 59812; hNatural Environment Research Council Isotope Geosciences Laboratory, Keyworth, Nottingham NG12 5GG, United Kingdom; iDepartment of Botany, Natural History Museum, London SW7 5BD, United Kingdom; jGNS Science, Lower Hutt 5040, New Zealand; kInstitut fur Mineralogie, Leibniz Universitat, D-30167 Hannover, Germany; lDepartment of Geology, University of Leicester, Leicester LE1 7RH, ¨ ¨ United Kingdom; and mDepartment of Earth and Atmospheric Sciences, University of Alberta, Edmonton, AB, Canada T6G 2E3

Edited by James P. Kennett, University of California, Santa Barbara, CA, and approved June 3, 2008 (received for review March 12, 2008)

A major obstacle in understanding the evolution of Cenozoic climate has been the lack of well dated terrestrial evidence from high-latitude, glaciated regions. Here, we report the discovery of exceptionally well preserved fossils of lacustrine and terrestrial organisms from the McMurdo Dry Valleys sector of the Transantarctic Mountains for which we have established a precise radiometric chronology. The fossils, which include diatoms, palynomorphs, mosses, ostracodes, and insects, represent the last vestige of a tundra community that